Antenna System Planning

Professional Customer Services All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

Radio Network Planning Expert Center Domain

Network Planning

Product

GSM B7

Division

Methods

Rubric

Antenna

Type

Guideline

Keywords Release Date

GSM, UMTS, antenna type selection, feeder length planning, TMA planning, tilt planning, diversity planning, mounting clearance,antenna separation, antenna pattern, A955, EMC 2003-Apr-29

E. SCHNEIDER (LUDWIGSBURG )

Antenna System Planning Abstract

This document summarizes previously written documents on antenna engineering and emphasizes the key engineering issues.

Reference Classification: 900 000 File Name: Ant_SystPl_ed01.doc Save Date: 2003-05-06

Revision Number: 008

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Predistribution

M.Hahn V. Stuhr K.Heinlein FJ.Klein R. Schwarz S. Hosseyni

PCS/RNE ACS/PS (ND)

B. Payer K. Daniel

All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

PCS/NPL/Methods PCS/NPL/Tools PCS/RNE PCS/RNE PCS/RNE PCS/RNE

Appraisal and Approval Authorities

Department

Name

Date

MND/BU-MRA/PCS

C. Brechtmann

PCS/NPL/Methods

M. Hahn

PCS/RNE

K. Heinlein

Signature

Distribution List

PCS

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(IDDL_Default)

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Contents


SCOPE .............................................................................................................................................................4 REFERENCED DOCUMENTS...............................................................................................................................5 RELATED DOCUMENTS AND INTERNET LINKS ....................................................................................................5 1 DOCUMENT OVERVIEW .................................................................................................................................6 2 RULES FOR ANTENNA PLANNING ..................................................................................................................6 2.1 Selection of antenna type .............................................................................................................................6 2.2 Planning antenna feeder length..................................................................................................................12 2.3 Planning TMA usage for GSM.....................................................................................................................14 2.4 Antenna height planning............................................................................................................................18 2.5 Planning the antenna azimuth ....................................................................................................................20 2.6 Downtilt planning ......................................................................................................................................20 2.7 Antenna diversity planning .........................................................................................................................25 2.7.1 Rx Diversity gain .....................................................................................................................................26 2.7.2 Rx space diversity ....................................................................................................................................27 2.7.3 Polarization diversity................................................................................................................................28 2.7.4 GSM space and polarization diversity on UL .............................................................................................30 2.7.5 Further rules on diversity..........................................................................................................................30 2.7.6 UMTS-FDD Tx diversity ............................................................................................................................31 2.7.7 UMTS FDD 4-RX diversity on UL...............................................................................................................34 2.8 Intra-system and inter-system compatibility assessment for site sharing ..........................................................36 2.8.1 How to ensure the intra-system and inter-system compatibility? ..................................................................38 2.9 EMC impact on antenna system planning....................................................................................................43 2.10 RNP tool related aspects on antenna planning ...........................................................................................43 3 RULES FOR ANTENNA INSTALLATION ...........................................................................................................44 3.1 Mounting rules for tower, mast, roof, wall mounting of antennas ...................................................................44 3.1.1 Side mounting of omni macro antennas on mast/ tower ............................................................................44 3.1.2 Minimum macro antenna height mounting for roof top.............................................................................45 3.1.3 Maximum skew angle for wall mounting of directional macrocell antennas .................................................46 3.1.4 Microcell antenna mounting rules ............................................................................................................46 3.2 Spacing for single band antennas in dual band GSM900/GSM1800 scenario................................................47 3.3 Tilt angle implementation ...........................................................................................................................47 3.4 Azimuth angle implementation ...................................................................................................................47 ABBREVIATIONS ..............................................................................................................................................48 INDEX.............................................................................................................................................................49 APPENDIX A

FREQUENCY BANDS ................................................................................................................50

APPENDIX B

ANTENNA TYPES .....................................................................................................................51

APPENDIX C

ANTENNA SYSTEMS OPTIONS..................................................................................................52

APPENDIX D

OVERVIEW ON ANTENNA DOWNTILT ......................................................................................53

APPENDIX E

OVERVIEW ON ANTENNA DIVERSITY........................................................................................54

APPENDIX F

PRINCIPLE OF AIR COMBINING................................................................................................58

APPENDIX G

ANTENNA PATTERN DISTORTION FOR DIFFERENT MOUNTING SCENARIOS ...........................58

APPENDIX H

INTRA-/INTER-SYSTEM COMPATIBILITY......................................................................................61

APPENDIX I

MISCELLANEOUS.....................................................................................................................63

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Readership Profile Content Summary

The target group is: engineers planning GSM radio networks. This document summarizes previously written documents on antenna engineering and emphasizes the key engineering issues. The main focus of this document lies on antenna engineering for GSM networks. Where applicable, the considerations were extended for UMTS. Not in the scope of the document edition 01 are: indoor and repeater application, smart antennas, inter-system compatibility issues.

Service Information Please send your comments, update wishes referring to this document to [email protected]. They will be considered in a next edition of the document. To get into contact with the Radio Network Planning Expert Center on antenna topics, please use the intranet link of Professional Customer Services under http://aww-mnd.alcatel.de/pcs/Antennas.

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SCOPE


REFERENCED DOCUMENTS [1.1] [1.2] [1.3] [1.4] [1.5]

3DF 00995 000 PGZZA Memo Technical Sheet 3DF 01902 2011 VAZZA 3DC 21150 0263 TQZZA

[1.6]

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[2.1] [2.2]

3BK 10023 0001 DSZZA Memo

[2.3]

Memo

[3] [4.1]

3DF 00995 0000 DSZZA 3DC 20008 0001 UZZZA

[4.2] [5.1] [6.1] [6.2] [6.3] [7.1] [7.2] [7.3] [7.4] [7.5]

3DC 20008 0003 UZZZA 3DC 21019 0005 TQZZA ND Design Paper TD Memo Technical Sheet Memo Memo 3DC 21144 0024 TQZZA Memo 3DC 20001 0010 UZZZA

[7.6]

3DC 20001 0014 UZZZA

[7.7] [7.8] [8]

3DC 21083 0001 TQZZA 3DC 21083 0003 TQZZA ed 02, draft

[9] [10]

3DF 00983 1050 DSZZA William C.Y. Lee

Antenna Engineering Rules Use of TMA for G3/G4 BTS in GSM1800 TMA for UMTS Using GSM900 High Power TRX GSM 900, GSM 1800 Use of High power TRX with TMA (white paper) TMA configurations for GSM and impact on network design Aspects on Polarization Diversity Considerations of Cross Polarized Antennas for Radio Network Planning Performance of Cross Polarized Antennas in Rural Areas (summary of dipl. thesis, Sept 1999) Physical Specification of Standard Antenna Set Hardware commercial configurator for antenna systems Content of Saleable Items for Antenna Systems Site Sharing GSM-UMTS Rf Aspects (version 04) DL Analysis Tx Diversity Transmit diversity in UTRA/FDD 4-Ways Rx Diversity for UMTS Enhanced Diversity with G4 TRE BTS cell split FFD: Cell split over 2 BTSs in Release B7 GSM product range Hardware Commercial Configurator for EVOLIUM™ A9100 Base Station Hardware Commercial Configurator for EVOLIUM™ A910 Micro-BTS EVOLIUM™ A9100 BTS Product description EVOLIUM™ A910 µ BTS Product description Dual Band Network Engineering; Network Design, Planning and Operational Aspects Consideration of antenna diagrams A955 (V5, V6) Mobile Cellular Telecommunications Systems

RELATED DOCUMENTS AND INTERNET LINKS [A 1]

Antenna Data Sheet database; consistent with [4.2] http://aww.stgl.sel.alcatel.de/pub/mcd/mps/ant/index.htm

[RFS 1]

Application note APN008: Isolation/Co-siting, Oct 00, http://www.rfsworld.com

[RFS 2]

RFS white paper: Using continuously adjustable electrical downtilt antennas to optimize wireless networks, Feb 01 Celwave Antenna datasheets and patterns http://selldoc.rfsworld.com/IndoorDocs/Mobile%20Commu nication%20Antenna%20Systems/Antennas/

[RFS 3]

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[KAT 1]

Memo (Kathrein) The influence of reflections on radiation patterns

[KAT 2]

Kathrein antenna datasheets and patterns http://www.kathrein.de/de/mca/produkte/index.htm

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1 DOCUMENT OVERVIEW

?

antenna planning (ch. 2)

?

antenna installation (ch. 2.9)

Additional background information is given in the document annex on different antenna topics: frequency bands, antenna types, antenna systems options, downtilt, diversity, air combining, pattern distortions and interference mechanisms. General remark: throughout this document, GSM900 stands for P-GSM900 if not explicitly stated; issues related to E-GSM900 are clearly marked.

2 RULES FOR ANTENNA PLANNING This chapter gives rules for the selection of antenna type, feeder length planning, TMA planning, antenna height and azimuth planning, downtilt planning, diversity planning.

2.1 Selection of antenna type This chapter gives rules for the selection of antenna type for different application cases: macro/microcell, single/dual/triple band. General info on antenna types can be found in APPENDIX B . The Alcatel saleable antenna items described in [4.1], [4.2] and [A1] must be preferably selected by radio network planning to the maximum possible extent to minimize the number of different antennas in Alcatel offers/projects; they are based on the specification given in [3] for ?

single band (GSM850, P-GSM9001, GSM1800, GSM1900, UMTS),

?

dual band (P-GSM900/GSM1800, GSM850/GSM1800, GSM850/GSM1900, PGSM900/UMTS, GSM1800/UMTS)

?

broadband (GSM1800 /UMTS)

?

triple band (GSM900/GSM1800/UMTS)

Remarks to dual band: ?

BSS software release B7.2 only supports the combinations P-GSM900/GSM1800, GSM850/GSM1800 and GSM850/GSM1900; currently there is no market demand for GSM900/GSM1900.

?

the frequency combination GSM1900/UMTS is covered by broadband antennas

General rule: It is recommended to select the same antenna type +antenna feeder for all sectors of a site. This minimizes the logistic effort for antennas, feeders mounting kits, clamps, etc. but also reduces the risk of installation errors . Reminder: for a given frequency band, the radome length decreases with increasing vertical HPBW; for a given vertical HPBW, the radome length decreases with increasing frequency band. Single band macrocell application

1

Depending on the application environment the general antenna selection rules of Table 1, Table 2, Table 3 apply. The table contains standard antennas which can handle most of applications. The antennas are recommended for usage in air combining configuration. To select the right downtilt for the antenna, the downtilt planning must be done first, see chapter 2.6.

the P-GSM 900 antenna specification can hold also for E-GSM 900

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Main tasks of the document edition 01 are to give rules for:


Morphoclass dense urban, urban suburban rural highway coverage

Horiz. HPBW [°] 65 65 90 90 360 65 33

Vert. HPBW [°] ˜ 6.5 9 7-8.5 7-8.5 ˜7 7-8.5

GSM 850/GSM 900 Gain [dBi] El. Tilt [°] =17 =16.5 =16 =16 11 =17 =18

6 6 2-6 2-6 2 6 0

Polarization Xpol Xpol Xpol vert. vert. vert. vert.

Ant. size [m] =2.5 =2.0 =2.6 =2.0 =2.5

Remarks 1 2 2, 3 4 5

Table 1: GSM 850/GSM 900; Key parameters for macrocell single band antenna Morphoclass dense urban, urban suburban rural highway coverage

Horiz. HPBW [°] 65 90 90 360 65 33

GSM 1800/GSM Vert. Gain [dBi] HPBW [°] ˜ 6.5 =17 7-8.5 =16 7-8.5 =16 ˜7 11 7-8.5 =17 =18

1900 El. Tilt [°]

Polarization

6 2-6 2-6 2 6 0

Xpol Xpol vert. vert. vert. vert.

Ant. size [m] ˜ 1.3 ˜ 1.3 ˜ 1.3 ˜ 1.3

Remarks

2 2, 3 4 5

Table 2: GSM 1800/GSM 1900; Key parameters for macrocell single band antenna Morphoclass dense urban, urban suburban rural highway coverage

Horiz. HPBW [°] 65 90 90 360 65 33

Vert. HPBW [°] ˜ 6.5 7-8.5 7-8.5 ˜7 7-8.5

UMTS Gain [dBi]

El. Tilt [°]

Polarization

=17 =16 =16 11 =17 =18

V V V V V V

Xpol Xpol vert. vert. vert. vert.

0-8 0-8 0-8 0-8 0-8 0-8

Ant. size [m] ˜ 1.3 ˜ 1.3 ˜ 1.3 ˜ 1.3

Remarks 6 2, 6 2, 3, 6, 7 4, 6 5 ,6 6

Table 3: UTMS; Key parameters for macrocell single band antenna The following notation is used: ?

For the downtilt: 2° means a fix electrical tilt of 2°; 2-6 means a fix electrical tilt in the range 2°-6°; V 0-8 means a variable electrical tilt in the range 0°-8°.

?

for the gain: =16 dBi, means minimum 16 dBi ; it must be the maximum offered in this category (while freezing the rest of parameters).

Remarks:

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1.

The recommended antenna type for coverage reasons is the one with the maximum gain offered in this category. But this may not be acceptable by the operator for dense urban, urban environment if its height > 2 m. If this is the case the antenna with =2.0 m must be considered whith less gain. For dense urban (high density areas), urban: the coverage between sectors with 65° antennas is achieved by increased scattering in these environments.

2.

For suburban, rural: the cell overlap with 90° antennas between the sectors is usually sufficient to allow successful handovers.

3.

Same standard antenna as for suburban, but cross polar antenna usage is not recommended, prefer using single polarized antennas and space diversity (see ch. 2.7).

4.

In rural areas: as an alternative, omni antennas can be used, but consider the pros and cons mentioned in APPENDIX B .

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Two solutions exist, depending on the type of the roadway arrangement: •

preferred: same 65° antenna as for dense urban but vertical polarized. If necessary, according to the current morphoclass, uptilt must be applied to get the desired cell range.

•

for exceptional cases or straight, rectilinear highway: 33° narrow beam antenna (Remark: two side by side coupled antennas of series AP 9065* (RFS) also lead to 33° horizontal HPBW for highway coverage)

6.

For UMTS, analogue parameters as for the lower frequency bands, but with V0°8° variable electrical tilt; reasons for the variable electrical tilt: a.) to be future proof for the remote tilt option, see APPENDIX D . b.) due to commercial reason: same price expected from preferred antenna suppliers.

7.

Currently UMTS is not foreseen to be deployed in rural areas; however, for the opposite case, the same recommendation is valid as for the other bands.

Influence of cell split feature on antenna selection for monoband sites If e.g. a 3x8 TRX monoband site is realized with the B7 feature “cell split over 2 BTS’s” (see [7.7]), the same antenna type and the same antenna numbers must be selected for each BTS rack, else the measured BCCH promises coverage in areas, what cannot be held by the TRX covering the other area. Single band microcell outdoor application

In the GSM850, GSM900, GSM1800, GSM1900 and UMTS bands, the antennas specified in Table 4 can handle most of applications. The range of the parameters is due to the fact, that the visual impact of the micro antenna has a higher influence on the antenna selection then its electrical properties.

Omni Sector

Horizontal HPBW 360° 85° ± 20°

Vertical HPBW 60° ± 20° 65° ± 20°

Gain 5 dBi ± 3 dB 8 dBi ± 3 dB

Table 4: Key parameters for microcell single band outdoor antenna Micro antenna selection rules: ?

For crossroad scenario with symmetrical streets or asymmetrical streets, use omni antenna; a sector antenna can be used as an additional option for crossroad scenario with asymmetrical streets.

?

For in-street scenario, wall mounting:

?

•

for coverage in 2 opposite directions: use bi-directional antenna

•

for coverage in 1 direction: use directional antenna

For the Alcatel Evolium A910 µBTS in •

low-loss configuration with air combining: the external sector antennas should be cross polarized.

•

single antenna configuration: the external sector antenna is vertical polarized

Remark: the internal integrated antenna of the Alcatel Evolium A910 µBTS matches the specified values of Table 4; its parameters are: Horizontal HPBW > 80°, Vertical HPBW = 65°±15°, Gain > 6.3 dBi, cross polarized, isolation between the 2 polarization branches > 25 dB; see the A910 product description [7.8]. 900/1800 macrocell dual band application

In a GSM900/GSM1800 dual band scenario, independent whether it is implemented with ?

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co-located single band cells (dual BCCH)

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5.


it is basically possible to use 3 technical solutions for antenna implementation: ?

solution 1: dual band antennas with variable electrical downtilt for each band

?

solution 2: single band antennas

?

solution 3: dual band antennas with fixed electrical downtilt

For the multiband cell the separate modification of the downtilt is a key instrument to tune the fieldstrength level difference between the 900 and 1800 bands to the values expected by the HO algorithms of B6/B7. The main criteria for selection among the above mentioned solutions is the coverage target; Table 5 makes a preference ranking for the solutions; for further details see Table 6 which gives a comparison of single band antennas vs. dual band antennas based on the implementation in Alcatel Evolium BTS shown in Figure 1.

multiband BSS (dual BCCH) multiband cell (single BCCH)

nb. TRX in 900 band low other cases low other cases

nb. TRX in 1800 band high high

Preference of solutions 1 > 2 >3 1 = 2 =3 1 >> 2 > 3 1=2=3

Table 5: Preference ranking of antenna solutions for dual band (assumption: preferred band=1800)

dual band antennas (solution 1, 3) + better suitability for multiband cell operation

single band antennas (solution 2) – not suitable for multiband cell (accurate identical azimuth setting required in 900 and 1800 is more difficult to achieve) – not ideal for coverage optimisation (separate + better for coverage optimization due to electrical but no separate mechanical tilt possible separate mechanical downtilt for 900 and 1800 in solution 1) (separate azimuth is possible but doesn’t represent a real advantage due to the goal to achieve a maximum overlap in 900/1800) + separate antenna configuration planning for both bands possible, e.g. 4 TRX in 900 (BTS standard configuration wired to one crosspolar 900 antenna) and 4 TRX in 1800 (BTS low loss configuration with air combining) 0 same number of feeders, (expensive costs for feeders, clamps and their installation can be reduced by diplexer usage; diplexer impact on coverage =1dB loss) + need of 2 external diplexers (if the dual band – need of 4 external diplexers antenna has 2 internal diplexers inside the radome) + twice less antennas (visual impact) – twice more antennas (visual impact) – higher antenna price; dual band antenna price > sum of 900+1800 antenna prices (subject to commercial conditions) + somewhat lower total cost for the site including hardware (antennas, cable, clamps) and installation labour

+ lower antenna price; sum of 900+1800 antennas< dual band antenna price (solution 2 is especially cheaper if initial antenna can be reused after migration from single to dual band operation) – somewhat higher total cost for the site including hardware (antennas, cable, clamps) and installation labour – twice more weight and wind load – higher pole required for vert. separation resp. more mounting space for horiz. separation

Legend: + advantage; – drawback for the solution; 0 equal rating

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X X

X

X

900

1800

Diplexer Tx/Rx/Rxdiv 900+1800

Diplexer

Tx/Rx/Rxdiv 900+1800 Tx/Rx/Rxdiv 900+1800 Tx/Rx/Rxdiv 900+1800

Diplexer

Diplexer Diplexer

Tx/Rx/Rxdiv Tx/Rx/Rx div 900 MHz



Evolium BTS

Diplexer

Tx/Rx/Rxdiv Tx/Rx/Rx div 1800 MHz Evolium BTS

Figure 1: Dual band antenna solution (here with integrated diplexer in the antenna) and single band antennas solution for Alcatel Evolium BTS Remarks to Table 5, Table 6: ?

The conclusions of Table 6, Table 5 mainly apply for the single operator case (1 operator colocates on a site 2 systems in GSM 900, GSM 1800). For the multioperator case, mainly solution 2 is applicable. But if there are EMC or mounting constraints imposed by local authorities, than operators may be forced to cooperate and make an antenna sharing with solution 1 or 3.

?

Solution 1: main advantages are separate electrical tilt tuning and better suitability for multiband cell operation; especially when used in a multiband cell with high QoS (CSR, CDR, HSR etc.) requirements and higher TRX number in the preferred band (e.g. 2x900+6x1800), solution 1 is the only recommended (the reason: in the multiband cell the intra-zone HO outer=>inner (900=>1800) is done with B7.2 HO cause13, which is based only on the outer zone level and –in B7-on the traffic balance between outer/inner zone; in cases with higher TRX number in the preferred band, MS’s will be often pushed in the inner zone to keep the load balance condition of cause 13, but this can lead to bad QoS if there is no perfect overlap of the inner and outer zones; with solution 1, the risks of solution 2 - like mismatching azimuths or non-clearance in the near field of one of the single band antennas- is eliminated; see [8])

?

Solution 2: main advantage is the individual mechanical tilt tuning; this advantage especially is relevant for high QoS requirements (CSR, CDR, HSR etc.) for colocated single band cells or multiband cell.

?

Solution 3: is a tradeoff for cases where the QoS requirements can be met with fixed down-tilts and especially fixed delta between GSM900 and GSM1800 fieldstrength level (cf. [8])

Antenna selection rules for the 900/1800 dual band macrocells: Depending on the application environment the general antenna selection rules of Table 7 apply for dual band antennas cf. solution 1 (for the selection of single band antennas cf. solution 2, refer to Table 1, Table 2). Table 7 contains antennas which can handle most of applications. The parameters are valid for both bands; the electrical tilt is variable and band independent. 10/64

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Table 6: Comparison of single band antennas vs. dual band antennas


Morphoclass dense urban, urban suburban rural highway coverage

900/1800, 900/UMTS, 1800/UMTS, 850/1800, 850/1900 Horiz. Vert. Gain El. Tilt Polarization Diplexer in the HPBW [°] HPBW [°] [dBi] [°] radome 65 ˜ 7.5 =17 V 0-8 XXpol yes 90 ˜ 7.5 =16 V 0-8 XXpol yes 90 ˜ 7.5 =16 V 0-8 vert. no 65 ˜ 7.5 =17 V 0-8 vert. no 33 =18 V 0-8 vert. no

Remarks 1 2, 3 4, 5, 6 7

Table 7: Key parameters for macrocell dual band antenna The following notation is used: ?

for the gain: =16 dBi, means minimum 16 dBi ; it must be the maximum offered in this category (while freezing the rest of parameters).

?

for the downtilt, V0°-8°T means a variable electrical downtilt in the range 0°-8°.

Remarks: 1. For dense urban (high density areas) and urban: the coverage between sectors is achieved by increased scattering in these environments. 2. For suburban, rural: the cell overlap between the sectors is usually sufficient to allow successful handovers. 3. A XXpol 90° antenna is recommended, but currently not offered by the Alcatel preferred antenna suppliers; e.g. Kathrein plans its market introduction for 3 Q 2003. 4. Same standard antenna as for suburban, but cross polar antenna usage is not recommended, prefer using single polarized antennas and space diversity (see ch. 2.7) 5. In rural areas: a standard omni dual band antenna is not specified due to its low market penetration, cf. APPENDIX B . 6. Currently UMTS is not foreseen to be deployed in rural areas. 7. In many projects, dual band coverage is planned for highway coverage only in exceptional cases; instead single band coverage is done. ?

If enough frequencies are available in the 900 band, typically this band is used due to its better coverage.

?

If (typically) more frequencies are available in 1800 band than in 900, than this band is used due to the higher capacity which can cope with the total traffic.

However, if it is desired to have dual band coverage, two solutions exist, depending on the type of the roadway arrangement: ?

preferred: same 65° antenna as for dense urban but vertical polarized. The tilts must be carefully tuned in both bands to get a matching coverage overlap.

?

for exceptional cases or straight, rectilinear highway: 33° narrow beam antenna; it is currently not offered by the Alcatel preferred antenna suppliers;

Rule for diplexer usage: diplexer usage is recommended, since: ?

it is cheaper to install external diplexers (at BTS side) and possibly at antenna connector side (if not already incorporated in the antenna radome) than to install a second feeder pair

?

at migration single => dual band, the old feeder system can be kept if the cable losses in the new band are still in the allowed range, i.e. =3 dB (see ch. 2.2).

Influence of cell split feature on antenna selection for multiband cell (single BCCH) If e.g. a 3x(4+4) TRX multiband cell is realized with the B7 feature “cell split over 2 BTS’s” (see [7.7]), by doing a migration from multiband BSS (dual BCCH), the previously installed antennas of the multiband BSS solution can be kept unchanged. 3DF 01902 2711 VAZZA

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1800/UMTS macrocell broadband application 850/1800, 850/1900 macrocell dual band application 900/1800,850/1800,850/1900, 900/UMTS,1800/UMTS microcell outdoor dual band application

For parameters see Table 7. For parameters see Table 7. Broadband antenna shall be selected only if commercially required (if cheaper). For parameters see Table 7. However, market availability strongly depends on the project demands. In many projects dual band microcell coverage is rather an exception. If (typically) more frequencies are available in 1800 band than in 900, than this band is used for single band coverage due to the higher capacity which can cope with the total traffic. As mentioned in the subchapter “Single band microcell outdoor application”, the visual impact of the µ antenna has a higher influence on the antenna selection than its electrical properties. So, deviations from the standard antenna parameters mentioned below are possible. Often, antenna manufacturers offer broadband µ antennas instead of dual band µ antennas, which cover the whole band from GSM850 to UMTS. The specified values of Table 4 are valid and hold for both bands. However, the sector antenna for the in-street scenario is cross polarized (XXpol) in both bands.

Triple band macrocell application

A triple band sector antenna for this case is defined by the parameters for all 3 bands: HPBW 65° (horizontal), 7.5° (vertical), gain 17 dBi, V0°-8 ° T variable and band independent electrical tilt, cross polarized (XXXpol) in all bands This is not a standard antenna, as it covers only a small application range.

Triple band microcell outdoor application

see subchapter “900/1800… microcell outdoor dual band application”

2.2 Planning antenna feeder length This chapter gives rules for feeder length dimensioning and feeder selection and illustrates them with practical examples.

Feeder characteristics

Exemplary feeder types used in Alcatel projects and their loss characteristics are given in Table 8. To retrieve these and further characteristics (e.g. bending radius), refer to the manufacturers catalogue.

Cable Type Diameter Supplier Losses in dB/100m series 900 MHz 1800 MHz 2200 MHz LCF 12-50 1/2” 6.80 9.91 11.10 RFS LCF 78-50 7/8” 3.87 5.73 6.44 LCFS 114-50 1 1/4” 2.77 4.15 4.68 LCF 158-50 1 5/8” 2.34 3.57 4.05 Table 8: Typical feeder types and losses in dB/100m, exemplary for Cellflex Low-Loss Foam-Dielectric Coaxial Cable (RFS) Jumper configuration Jumper cables have to be provided at the points A, B, C along the feeder path of Figure 3. Table 9gives the jumper cable configuration for sites with and without TMA; the number of jumpers is per feeder, i.e for a single band crosspolar antenna fed by 2 cables, the number of jumpers must be multiplied by 2 (see figure in APPENDIX C ).

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900/UMTS, 1800/UMTS macrocell dual band application


Feeder cable type LCF 12-50 LCF 78-50 LCFS 114-50 LCF 158-50

Jumper cable type

Jumper per feeder 0* 2 2 2

LCF 12-50 J jumper

Jumper per feeder on TMA sites 1* 3 3 3

Table 9: Jumper configuration

* Remark to Table 9:

From practical point of view it is better to use for the LCF 12-50 feeder cable type: - no jumper cables of type LCF 12-50 J jumper, if no TMA used (instead of 1) and - only 1 jumper cable of type LCF 12-50 J jumper if TMA used (instead of 2), between TMA and antenna. The reason is that LCF 12-50 J jumper and LCF 12-50 have the same loss and nearly the same handling/bending flexibility. Anyway, the LCF 12-50 feeder is usable only for short distances of 6-7 m, so additional jumpers are difficult to justify. For the LCF 12-50 J jumper cable of RFS the loss/m is given in Table 10 (without connector losses which must be added; a typical connector loss is <0.02 dB). LCF 12-50 J jumper loss

900 MHz 0.068 dB/m

1800 MHz 0.099 dB/m

2200 MHz 0.110 dB/m

Table 10: Insertion losses of jumper cable Typical lengths of the jumper cable LCF 12-50 J jumper are: 1m, 2m or 3m (where 2m, 3m are mostly used). Feeder length dimensioning

Rule: recommended maximum allowed attenuation (losses of feeder cable+jumper cables+connectors) between the BTS front end connector and the antenna connector is 3 dB (value typically used in practice). Exemplary, Table 11 give the maximum feeder length for the typical losses of RFS’s Cellflex cables mentioned in Table 8, considering the jumper configuration of Table 9 and the jumper insertion losses of Table 10. Analog, Table 12 gives the maximum feeder length for the case of TMA usage. Cable type

900 MHz

1800 MHz

2200 MHz

LCF 12-50

44.1

30.3

27.0

LCF 78-50

67

42.0

36.3

LCFS 114-50

93.6

58

50

LCF 158-50

110.8

67.4

57.8

Table 11: Recommended max. feeder length (m) assuming 2x LCF12-50 Jumper usage of 3m each (for 1/2 cable: no jumpers)

Cable type

900 MHz

1800 MHz

2200 MHz

LCF 12-50

35.2

23.2

20.5

LCF 78-50

51.4

29.8

25.0

LCFS 114-50

71.8

41.2

34.4

LCF 158-50

85

47.9

39.8

Table 12: Recommended max. feeder length (m) assuming 3x LCF12-50 Jumper usage of 3m each (for 1/2 cable: 1 jumper) and TX DL insertion loss of TMA (cf. Table 10) Feeder selection The antenna feeder have to be selected according to the following criteria: 3DF 01902 2711 VAZZA

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maximum allowed feeder length (see Table 11, Table 12)

?

site construction constraints (existing space in cable trays and wall breakthroughs, minimum allowed bending radius)

?

commercial conditions (price)

Selection rules: ?

It is recommended to select the same feeder type for all antennas of a site. This minimizes the logistic effort for feeders, mounting kits, clamps, etc. but also reduces the risk of installation errors .

?

Usually, the usage of the 1/2 “ feeder cable is not recommended; a breakeven calculation shows that the 1/2” cable offers less total loss vs. the 7/8” cable only for very small feeder length of 6-7 m.

?

The RNE must first try to use the 7/8” feeder cable due to its lowest price and highest handling flexibility; it can already cover many practical applications, due to the achieved length. If the required feeder length is longer than the value indicated in Table 11 for 7/8” the usage of next thickness class is recommended (1 ¼”). If 1 5/8” is still not long enough, the distance BTS-antenna must be reduced or the losses of >3 dB must be tolerated. One must keep in mind that for e.g. rural tower sites the feeder length must cover the exemplary distances as indicated in Figure 2. Feeder length:=2m+7m+(H tower-2m-0.5* H ant. radome)+2m ˜ H tower+8m, where 0.5* H ant. radome is approximized with 1 m.

H Tower Max. H planning A955

Lightning protection

jumper 2m

BTS shelter

2m

feeder

7m

2m

Figure 2: Rural site example; Feeder length + antenna height planning

2.3 Planning TMA usage for GSM This chapter gives rules for/shows the consequences of TMA usage and illustrates them on an example. For general remarks on TMA see APPENDIX C . Further related documents to this topic are [1.5], [1.6]. When to use TMA ?

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?

A TMA may be used in coverage driven (noise limited) environments (e.g. suburban/residential, rural, roads).

?

If the link budget is UL limited, a TMA usage may be sensible for high power (HP) TRX configurations and for suburban or rural sites with antenna height ≥ 20 m; its

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?

MAPL DL

benefits are the gain in cell range (due to gain in the maximum allowed path loss, MAPL) and the improvement of indoor coverage. DL no TMA Tx insertion loss

TMA contribution


MAPL UL

∆

UL no TMA

A TMA helps to improve the MAPL in a UL limited linkbudget only if 0 < ? - Tx insertion loss of TMA in DL < TMA contribution in UL where ?=MAPL (DL,no TMA) - MAPL (UL,no TMA)>0 and ? - Tx insertion loss of TMA in DL=improvement in linkbudget The breakeven of TMA usage for the business case is given in [1.6].

For a turnkey project in a coverage driven environment, the improvement in linkbudget must be at least: • 0.6 dB for area coverage with 3-sectored sites • 0.9 dB for road coverage with 2-sectored sites ?

If the link budget is DL limited, a TMA will show no effect on the cell range.

?

If the link budget is balanced, the TMA can be used as a network enhancing feature depending on the operator policy: it efficiently reduces the UL MS power yielding better MS standby times and reduced UL electromagnetic pollution levels. Also if the link budget is balanced and no power reduction for MS is done, the TMA helps to increase the UL throughput for GPRS and E-GPRS.

Table 14 and Table 15 indicate for GSM 900 and GSM 1800 in the environments suburban, rural, roads: the limiting link in the link budget and if a TMA is sensible or obsolete. The recommendation for TMA usage is based on the: ?

computation of typical link budgets for the Alcatel G4 Evolium A9100 BTS for MP and HP (see also [1.4], [1.5], [1.6]);

?

BTS output power at antenna connector for the used BTS configurations as given in [7.7]; combining/no combining stands for the operation mode of ANc module in the BTS;

?

TMA parameters for the present products in Table 13.

Band GSM 900 GSM 1800

Gain Noise figure TX insertion loss in DL 14 dB 1.8 dB 0.6 dB 12 dB 1.8 dB 0.4 dB Table 13: Most important TMA parameters

GSM 900 Medium Power TRX (MP) High Power TRX (HP) BTS config. without use TMA? BTS config. without use TMA? TMA TMA 3x2 no combining UL rather not (remark 3x2 no UL yes (remark 2) 1) combining 3x3 combining DL no 3x3 combining DL no 3x4 no UL yes (remark 2) combining* 3x4 combining DL no 3x4 combining DL no 3x6 combining* DL no 3x6 combining* DL no Remarks: * this BTS configurations is realized with 2 cabinets (B7 feature “cell split over 2 BTS”) 1. no, if benefit of TMA in MAPL is too low (e.g. 0.4 dB); to be checked case by case 2. benefit of TMA in MAPL is typically better than 1.6 dB

Table 14: GSM 900 – Typical link budget limitations and indication for TMA usage

GSM 1800 Medium Power TRX (MP) High Power TRX (HP) BTS config. without use TMA? BTS config. without use TMA? TMA TMA 3x2 no balance rather not (remark 3x2 no UL yes (remark 2) combining 1) combining 3x3 combining DL no 3x3 combining DL no

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UL

yes (remark 2)

3x4 combining DL no DL no 3x6 combining* DL no DL no Remarks: * this BTS configurations is realized with 2 cabinets (B7 feature “cell split over 2 BTS”) 1. no, if benefit of TMA in MAPL is too low (e.g. 0.4 dB); to be checked case by case 2. benefit of TMA in MAPL is typically better than 2 dB; see example in Table 16

Table 15: GSM 1800 – Typical link budget limitations and indication for TMA usage Remark to Table 14 and Table 15: ?

If the link budget for MP is already UL limited or balanced, the migration from a MP to a HP TRX in the same TRX configuration shows a benefit for the MAPL, only if the HP TRX is deployed together with a TMA.

?

Improvement (lowering) of the noise figure of the total receive chain =>getting a better sensitivity (desired) according to Friess formula => increased MAPL.

?

Degradation of the blocking and intermodulation characteristics of the BTS (not desired) i.e. risk to not fully comply with 3 GPP recommendation 05.05 regarding blocking and intermodulation for the case that the value of the TMA amplification gain (mostly fix cf. TMA data sheet, e.g. 12 dB) greatly exceeds the value of the losses between the antenna and the input of the base station, i.e. the losses of the feeder+jumper cables and connectors; This degradation may exist in the G3 and G4 BTS, because the excess gain compensation capability is =0 for 1-2 TRX (exactly the cases of major interest for the TMA application in GSM1800) .

Consequences of TMA usage

Measure to combat BTS blocking characteristics degradation ([1.2]): planning an antenna height = 20 m; realistic for rural, roads and possibly for suburban sites. Measure to combat BTS IM characteristics degradation: no measure, since required minimum coupling loss between the antennas of MS and BTS of typ. 100 dB cannot be achieved with realistic BTS antenna heights; however, the risk of having this IM created is extremely low and can be tolerated. If Alcatel suggests TMAs to operators whos gain greatly exceeds the losses of feeder+jumpers+ connectors, these need to be made aware of the possible 3GPP non compliance of that configuration. Impact of TMA on link budget

Example for TMA usage with HP TRX in GSM1800

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In case TMAs are present in the system, they have to be considered in the network design. ?

For the UL path of the link budget in a coverage driven scenario, the TMA impact cannot be treated by simply adding the TMA gain; instead the TMA contribution has to be added (the TMA contribution is the value indicating the BTS sensitivity improvement by the TMA). The calculations for the TMA contribution in UL are done with the Friess Formula (see APPENDIX C ).

?

In the DL path of the link budget the TMA will add a Tx insertion loss composed of the TMA insertion loss according to the data sheet (Table 13) and the loss of an additional jumper cable (Table 10).

Given is a 3x2 HP TRX no combining BTS configuration in rural environment with antenna height= 35m. Figure 3 shows the UL receive path for G3 (ANx) or G4 BTS (ANc) in GSM 1800.

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3x4 no combining* 3x4 combining 3x6 combining*

Antenna

Tower

A mounted RX B

C

D


Amplifier (MHA)

Frontend (ANX or E ANC)

F Splitter G (ANY)

H Splitter I (ANY)

J

Receiver (TRE)

BTS

Figure 3: UL receive path for G3 (ANx) or G4 BTS (ANc) in GSM 1800 For the calculations the following figures have been considered: ?

total cable loss (feeder plus jumpers) of 3.0 dB = 2.4+3*0.2 for 40m cable length 1.2 dB = 0.6+3*0.2 for 10m cable length •

feeder Cable losses cf. Table 8: 2.4 dB (40m) and 0.6 dB (10m)

•

usage of 3 Jumper cable of 2 m each (at point A, between antenna/TMA; point B, between TMA/feeder cable and point C between feeder cable/BTS) Losses per jumper cable=0.2 dB for GSM1800, cf. Table 10.

?

Selecom TMA technical data according to datasheet, see Table 13

?

for a G3 BTS with a Noise Figure 4dB, a S/N = 6dB leads to a sensitivity of –111dBm, since: sensitivity = -174 dBm + 10*log (200 kHz)+S/N + system noise figure= -121 dBm+ S/N + BTS noise figure= -121+6+4 = -111 dBm

Table 16 gives the exemplary impact of TMA usage for GSM 1800HP TRX. The TMA contribution (benefit) is calculated with the Friess formula (see APPENDIX C ) compared to the same BTS configuration without TMA and the same total cable loss The new system sensitivity (taking into account the TMA presence) to be considered in the link budget is calculated in Equation 1: new system sensitivity= -111 dBm - |TMA contribution| Equation 1: BTS sensitivity calculation due to TMA usage The benefit of TMA for the MAPL is lower then the TMA contribution since the link budget gets DL limited through the TMA introduction. TMA Gain [dB] 12 12

Antenna height [m] 35 35

Cable TMA New BTS Benefit of TMA length contribution Sensitivity for the MAPL [m] [dB] [dBm] [dB] 40 4.2 -115.2 2.1 10 2.6 -113.6 2.1 Table 16: Exemplary impact of TMA usage for GSM 1800 HP TRX

Gain in cell range [%] 14 14

Blocking & IM degradation [dB] 9 10.8

Remark: the blocking degradation (resp. IM degradation) of Table 16 is taken into account for the calculation of the required minimum separation (i.e of the required minimum coupling loss) between the antennas of the MS and of the BTS by subtracting the degradation value from the 3GPP specified maximum allowed in-band blocking level for the BTS (resp. from the 3GPP specified maximum allowed IM level caused by 2 MS in the receiver front end of the BTS). Conclusions on the example: If a TMA with 12 dB gain is applied the benefit for the MAPL is maximum of 2.1 dB. The improved UL sensitivity leads however to a degradation in terms of blocking resp. intermodulation cf. Table 16; but this can be combated resp. tolerated as shown in the section “Consequences of TMA usage”.

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2.4 Antenna height planning

It is quite hard to give a general guideline for antenna height only in function of the morphostructure. Though, the selection of the antenna height, shall be done based on: ?

simulations (fieldstrength, coverage, interference probabilities) with a RNP tool such as A955, taking into account the morphostructure, the topography, building geometry etc., to meet the QoS requirements in the cell (fieldstrength, coverage probability);

?

necessary clearance in the antenna near field range (cf. Equation 7 , chapter 3.1 for flat roof);

?

site constraints, due to •

existence of adjacent operator(s) on site;

•

maximum mast heights (see below).

The selected antenna height has a strong impact on the cell coverage range and interference situation in the vicinity. The higher the antenna height, the bigger the coverage area is, but also the potential interference area. Especially in the areas where Alcatel doesn’t face any coverage commitment, one should try to minimize the antenna height to a value, guaranteeing coverage e.g. for the intended village, but not covering the tree areas around. Reason: minimize site construction costs (see next subchapter). Maximum mast heights

For macrocells mounted on masts, two types of masts are used: guided masts (70-80% of cases) and self supporting masts. They are typically offered in the height classes mentioned in Table 17, but the availability of classes may differ on a Alcatel project basis. If possible, the RNE must try to minimize the antenna height to a value fitting into the next lower mast height class given in Table 17, in order to save installation costs. The top of the sector antenna radome may reach the top of the tower but never overtop it due to the lightning protection of the tower.

Guided mast heights [m] Self supporting mast heights [m] 21 Table 17: Mast height classes [m]

26

29 31

35 36

41 41

47 46

53 51

Further issues 1.

Typical µcell antenna heights

Field proven values for µcell antenna height are 3 –15 m and below rooftop, whereas the umbrella cell antenna height are 15 – 35 m. In cases with very high buildings, µcell antenna height can be > 10m; the big µcell can relief from traffic congestion in umbrella cell. But the risks associated to high µcell antenna heights are also present if the frequency spectrum doesn’t allow an optimized frequency plan: -for outdoor MS served by the high µcell, the risk to get the UL disturbed by a neighbour macro site increases with increasing µcell antenna height -for indoor MS located in higher building floors and served by the high µcell, there is a risk of DL+UL interference. If the target is to relieve hot spot macrocell from in building traffic, dedicated indoor solutions must be evaluated.

2.

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Impact of close proximity scenario on µcell antenna height

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This chapter gives rules for planning the GSM antenna height, which is key result of the RNP process.

Impact on antenna engineering: choice of µcell antenna height below rooftop, to prevent from receiver blocking of the µBTS receiver (in UL path). However, problems due to the close proximity scenario were never reported from the field. For a description of the close proximity scenario see APPENDIX I . All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

3.

Influence of antenna height on space antenna diversity separation

According to Equation 3 in ch. 2.7.2 the separation of the diversity antennas must be: d_horiz > effective antenna height/10 . 4.

Antenna heights in dual band case with single band antennas (solution 2 in chapter 2.1)

It is recommended to mount the higher band antennas above the lower band antennas to partially compensate weaker propagation conditions in lower frequency band (e.g. 1800 antennas above 900 antennas). 5.

Impact of cell split feature on antenna height

If e.g. a 3x8 TRX monoband site is realized with the B7 feature “cell split over 2 BTS’s” (see [7.7]), the same antenna height must be selected for the Tx resp. for the Rx antennas of each BTS rack. If e.g. a 3x(4+4) TRX multiband cell is realized with the B7 feature “cell split over 2 BTS’s” (see [7.7]) by using separate single band antennas (solution 2, see chapter 2.1) the same rule as in the previous point applies. 6. Antenna height planning for hopping networks:

Hopping type

impact on interference situation in network same antenna height

regular antenna azimuth

tilt tuning

Remarks

RFH 1x3

+

+

+

a

RFH 1x1

++

O

++

a

BBH

O O O Table 18: Impact of height, azimuth, tilt planning for hopping networks

b

Remarks on Table 18: ?

Generally in RFH networks, it is necessary to achieve a minimum coverage overlap (to reduce interference) which still allows secure HO between cells. •

With a reuse scheme of 1x3: RFH is most efficient if the network design is regulary, i.e same antenna heights, regular antenna azimuths.

•

With a reuse scheme of 1x1, the same frequency group is used everywhere; here the requirement to have same antenna height is even higher as for 1x3, whereas there is no requirement for same azimuth.

?

For BBH networks there are no such constraints on network design.

7.

Consideration of antenna height in A955 RNP tool

Reminder for RNE (see Figure 2): ?

antenna height used for tool predictions := height above ground of Tx antenna radome center.

?

maximum allowed sector antenna height for the tool predictions:= tower/mast/pole height (without lightning protection) – 0.5* radome size The top of the sector antenna should never trespass the top of tower/mast/pole due to the existing lightning protection for the construction. Example: for a 31 m mast height, the maximum allowed antenna height for the A955 prediction in GSM 1800 with a typical antenna height of 1.3 m is 30m (in fact 30.4m=31m-1.3/2). The antenna connectors at the antenna bottom will be at 29.7 m.

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2.5 Planning the antenna azimuth

General rules for azimuth planning:

Dual band GSM900/GSM1800 scenario

Hopping networks

?

For a standard planning, with a standardized 3 sector arrangement, the antenna azimuth is planned following a fixed grid pattern with sector direction e.g. 60°,180° and 300°.

?

In urban areas it may not be sensible to direct the main beam of a sector along a straight rectilinear road since this ensures a larger cell range then planned for this morphoclass. The following scenario is possible: a MS far from the site on the road may still be booked on the site due to direct line of sight along the road, whereas the monitored neighbours in the neighbour list do not offer anymore a sufficient level for a secure HO; if the serving cell level further decreases, a call drop is possible.

?

For 2 sector sites on roads in rural area the main beams must follow the direction of the road.

For the co-located dual band TRX’s in GSM900/GSM1800 scenario the planning of the antenna azimuth is a critical issue: ?

For the co-located single band cells (where solutions 1, 2, 3 of chapter 2.1 are possible) it is recommended to achieve a maximum coverage overlap in both bands by planning antenna azimuths identical in both bands. Reason: multiband MS benefit most from the traffic distribution between bands if the coverage overlap is maximum; for single band MS’s there is no impact.

?

For the multiband cell (where solutions 1, 3 of chapter 2.1 are favoured vs. solution 2) this is even mandatory to do so. Reason: there is no BCCH reception in that regions of the inner zone which do not overlap with the outer zone.

See subchapter “Further issues” in 2.4.

2.6 Downtilt planning This chapter gives rules for planning the antenna downtilt in GSM; in UMTS-FDD extensive field experience on the tilt-traffic dependency must be acquired on the field. General remarks on downtilt for all frequency bands are given in APPENDIX D . Goal of downtilt planning

Principle

The goal of downtilt planning is: ?

for urban areas, to find a tradeoff between maximum fieldstrength level at cell border and interference reduction;

?

for rural areas, to ensure a maximum fieldstrength level at cell border (good fringe coverage).

The downtilt planning is done with a geometrical ray optics method under consideration of: ?

vertical HPBW of the BTS antenna

?

BTS and MS antenna height above ground

?

effective BTS antenna height (see Figure 6) which takes into account the topography between BTS and MS location

?

morpho-structure in the vicinity of the BTS antenna.

Figure 4, Equation 2, Table 19 show the principle under the simplifying assumption of flat terrain. 20/64

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This chapter gives rules for planning the antenna azimuth, which is key result of the RNP process. First some general rules are given, then some particular cases are treated.

HPBW main beam direction All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

HPBW

2° downtilt 7° vertical HPBW

a

b

4° downtilt 7° vertical HPBW

tilt H HPBW a

main beam dir. b

c

Figure 4: Assessment of required tilts There is a strong impact of vertical antenna pattern on the minimum efficient downtilt angle. The downtilt angle is efficient, only if it is bigger than ½ of vertical HPBW (see Figure 4 and Table 19). For the example of vert. HPBW = 7° a minimum efficient downtilt angle is 4°. It is possible to further increase the downtilt, e.g. until the vertical pattern’s minimum between the main beam and the 1st upper side lobe is oriented towards the horizon. For a vertical HPBW = 7° the first upper side-lobe lies on the horizon line at an downtilt angle of 8°–9°. Equation 2 gives the rules for calculation of required tilt according to the desired coverage range using geometrical ray optics. It gives the dependency of position of points c (corresponding to the upper 3 dB point in the vertical pattern), b (corresponding to the main beam) and a (corresponding to the lower 3 dB point in the vertical pattern) of the antenna height above ground (“H”), the required electrical + mechanical downtilt angle (“tilt”) for the main beam and the antennas vertical HPBW (“HPBW”).

c=

H H H ; b= ; a= tan( tilt − HPBW / 2) tan( tilt ) tan( tilt + HPBW / 2) Equation 2: Tilt assessment with geometrical ray optics

Remark to Equation 2: If e.g. the height ‘H’ is fixed by constraints and the resulting value for ‘tilt’ is relative high (>20°) it is worth it to look for alternative lower sites and/or select another antenna with a more narrow vertical pattern. Reason: high risk for pattern distortions for the case of flat roof mounting of the antennas. A calculation example (for qualitative purpose only) is given in Table 19: Downtilt [°] 1 2 3 4 5 6 7 8

Dist. of point a [km] 0.38 0.31 0.26 0.23 0.20 0.18 0.16 0.15

Dist. of point b [km] 1.72 0.85 0.58 0.43 0.34 0.29 0.24 0.21

Dist. of point c [km] over radio horizon over radio horizon over radio horizon 3.44 1.14 0.69 0.48 0.39

Table 19: Exemplary calculation of points a, b, c positions for antenna height = 30 m, vert. HPBW = 7°, flat terrain

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Figure 5, Table 20 and Table 21 show how the tilt is determined as function of morphoclass and coverage range under the simplifying assumption of flat terrain. With Equation 2 it is possible to adjust cell overlap areas during the initial network design phase, as shown in Figure 5; this first design may be subject for a later optimization. Case 1: tilt planning for dense urban, urban environment The tilt planning is done for point c in Figure 4, i.e. the upper –3dB lobe of the vertical pattern is directed towards the calculated cell range. It is assumed that multipath propagation ensures for this 3 sectorized cell arrangement a sufficient cell overlap for a secure handover (to be validated on the field). The required tilt can be read out of Table 20 exemplary for a vertical HPBW=7°; here the cell range may be indoor/incar/outdoor cell range based on coverage and/or capacity requirements in the cell. If the required tilt doesn’t match the electrical tilt for the selected antenna in Table 1 an additional mechanical uptilt/downtilt must be applied. Further, if this tilt planning leads to HO drop due to ?

level (bad coverage) between some distinct sites, less downtilt must be applied, e.g. by using mechanical uptilt;

?

interference between some distinct sites, more downtilt must be applied.

Advantages of this tilt planning are: ?

frequency reuse improvement through interference reduction further away from site

?

improvement of indoor coverage close to the site.

Case 2: tilt planning for suburban, rural, highway environment The tilt planning is done for point b in Figure 4, i.e. the main beam of the vertical pattern is directed towards the calculated cell range. The required tilt can be read out of Table 21. If the required tilt doesn’t match the electrical tilt for the selected antenna in Table 1 an additional mechanical uptilt/downtilt must be applied. For rural areas with big cell ranges, pointing the main beam towards the targeted cell border, can yield downtilt of ˜ 0°=arc tan (mast height/cell range). Advantages of this tilt planning: good fringe coverage.

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Required tilt

Case 1: Dense urban, urban coverage; Tilt planning for point c (Intersection plane X-X) Tilt 2

Site A

Tilt 2 be e lo Sid

Ma in be am


Site B

Cell range R2

0.5* R2

Inter Site Distance A-B = 1.5* R2

X

A

B

R2

X

0.5* R2

Case 2: Suburban, rural, highway coverage; Tilt planning for point b Tilt 1

Tilt 1

Site C

Ma in b eam

Site D

eam in b Ma

Cell range R1

Cell range R1

Inter Site Distance C-D = 2* R1

Figure 5: Tilt planning for different environments

cell range [m]

Antenna height [m] 30 35

15

20

25

40

45

50

300 400

6.4 5.6

7.3 6.4

8.3 7.1

9.2 7.8

10.2 8.5

11.1 9.2

12.0 9.9

13.0 10.6

500 600

5.2 4.9

5.8 5.4

6.4 5.9

6.9 6.4

7.5 6.8

8.1 7.3

8.6 7.8

9.2 8.3

700 800 900

4.7 4.6 4.5

5.1 4.9 4.8

5.5 5.3 5.1

6.0 5.6 5.4

6.4 6.0 5.7

6.8 6.4 6.0

7.2 6.7 6.4

7.6 7.1 6.7

1000 1300

4.4 4.2

4.6 4.4

4.9 4.6

5.2 4.8

5.5 5.0

5.8 5.3

6.1 5.5

6.4 5.7

1500 1700

4.1 4.0

4.3 4.2

4.5 4.3

4.6 4.5

4.8 4.7

5.0 4.8

5.2 5.0

5.4 5.2

2000

3.9

4.1

4.2

4.4

4.5

4.6

4.8

4.9

Table 20: Downtilt (electrical+mechanical) in degrees referring to case 1 of Figure 5 (vertical HPBW=7°)

Antenna height [m] cell range [m] 300 400 3DF 01902 2711 VAZZA

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20

25

30

35

40

45

50

2.9 2.1

3.8 2.9

4.8 3.6

5.7 4.3

6.7 5.0

7.6 5.7

8.5 6.4

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1.7

2.3

2.9

3.4

4.0

4.6

5.1

5.7

600 700

1.4 1.2

1.9 1.6

2.4 2.0

2.9 2.5

3.3 2.9

3.8 3.3

4.3 3.7

4.8 4.1

800 900

1.1 1.0

1.4 1.3

1.8 1.6

2.1 1.9

2.5 2.2

2.9 2.5

3.2 2.9

3.6 3.2

1000 1300

0.9 0.7

1.1 0.9

1.4 1.1

1.7 1.3

2.0 1.5

2.3 1.8

2.6 2.0

2.9 2.2

1500 1700

0.6 0.5

0.8 0.7

1.0 0.8

1.1 1.0

1.3 1.2

1.5 1.3

1.7 1.5

1.9 1.7

0.4 0.6 0.7 0.9 1.0 1.1 Table 21: Downtilt (electrical+mechanical) in degrees referring to case 2 of Figure 5

1.3

1.4

2000

Further rules on downtilt

?

The tilt angles can be implemented only with a resolution of 0.5°, see also ch. 3.3.

?

Prefer electrical vs. mechanical downtilt (refer to APPENDIX D ).

?

Tx and all Rx antennas must have the same tilt.

?

If e.g. a 3x8 TRX monoband site is realized with the B7 feature “cell split over 2 BTS’s” (see [7.7]), the same tilt must be selected for all antennas on each BTS rack.

?

For microcell and picocell antenna downtilt is not recommended. Reason: for these very small antennas (i.e. length up to a few tens of cm) with a typical vertical HPBW between 45° and 80°, downtilt is beneficial in terms of field strength reduction only with relative high tilt angles (35° to 50°).

?

In a 900/1800 multiband cell scenario (single BCCH, independent whether it is realized with one BTS or with the B7 feature “cell split over 2 BTS’s”) where the HO algorithms (e.g. cause 13) assume a constant fieldstrength level difference between 900/1800 bands, it is recommended (especially for indoor places with high 1800 TRX ratio) to match the fieldstrength level distributions (along the distance) for the 900/1800 bands by •

setting different downtilt values for 900 and 1800 bands (typically lower tilt value for 1800) or

•

possibly selecting single band antennas with different antenna gains and vertical patterns (high RNE effort).

This helps to divert the 900 traffic into the 1800 band with the required QoS and to efficiently use the high number of 1800 TRX’s. A955 RNP tool simulations and sample measurements recorded in the respective places help to determine the downtilt settings (see [8]).

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?

In RFH networks, it is necessary to achieve a minimum coverage overlap (to reduce interference) which still allows secure HO between cells. For a reuse scheme of 1x3 and even more for 1x1 a careful tilt tuning is recommended.

?

Combination of mechanical and electrical tilt for GSM : •

Choosing sector antennas with high electrical downtilt (6°...8°) and applying mechanical uptilt in main beam direction is a very effective means for interference and range reduction in side lobe direction. The high high electrical downtilt + mechanical uptilt is a favoured solution vs. low electrical downtilt + additional mechanical downtilt.

•

For very high antenna locations (e.g. on the tops of high mountains, or on the roof-tops of tall buildings for coverage in the street below) a combination of electrical and mechanical downtilt is recommended.

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Tilt consideration in RNP tools ?

The antenna manufacturers typically provide two cuts through the radiation pattern in horizontal and vertical direction. Mathematically, there is no exact method to rebuild a three-dimensional structure from two two-dimensional cuts. So assumptions and simplifications are made. Different planning tools have different approaches, as no exact solution exists. Refer to [9] for A955’s approach description (valid for V5 and V6 of A955). Also consider, that A955 does not consider three-dimensional radiation patterns provided by some antenna manufacturers for parts of their product range.

?

If a manufacturer provides for a variable electrical tilt antenna several patterns (e.g. one pattern per tilt value), it is recommended to create as many antenna types as tilt values, to be able to use all patterns. Reason: within A955 tool, an antenna type can have only one pattern (horiz. and vert.). See also the section “Handling of cross polar antennas in RNP tools” in ch. 2.7.3.

2.7 Antenna diversity planning This chapter gives rules for planning antenna diversity in GSM and UMTS-FDD: this comprises the Rx diversity, Tx diversity, space diversity and polarization diversity. General remarks on antenna diversity are given in APPENDIX E and APPENDIX F . Impact on service coverage

Antenna diversity has only an impact on the service coverage, if the system is UL limited. It needs to be checked with a linkbudget for the installed equipment, if there will be an impact on the cell range in UL, see also Table 14, Table 15. If the linkbudget is DL limited by e.g. 2 dB, there will be no improvement in the service coverage when improving the UL with better diversity gain.

Summary

Table 22 summarizes the GSM rules for diversity planning. For additional details refer to the following subchapters.

Environment

recommended diversity type

Rx Div. gain (UL)

dense urban+urban + suburban

crosspolar diversity

˜ 3 dB

rural, highway

space diversity

for horizontal separ.:˜ 5 dB for vertical separ.:˜ 3 dB

Addit. Tx loss (DL) for crosspolar diversity ˜ 0 dB

1.5 to 3 dB

Comparison of diversity types for the environment crosspolar diversity: +lower visual impact of antennas +˜ same Rx diversity gain in NLOS areas as with space diversity +air combining possible with ≤ 4 TRX * space diversity: higher visual impact of antennas - air combining possible only with ≤ 2 TRX* crosspolar diversity: -negligible Rx diversity gain in NLOS areas

-additional Tx loss of ˜ 1.5 to 3 dB space diversity: + high Rx diversity gain in NLOS areas + no Tx loss +higher visual impact of antennas not as relevant as in urban environments *provided, that the requirement is to have max. 2 antennas per sector in dense urban+urban + suburban Table 22: Summary table with rules and key parameters for GSM diversity planning (+=advantage; –=drawback)

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2.7.1 Rx Diversity gain Table 23 presents the overview on diversity gains for space and polarization diversity in different environments for GSM900/1800. The bold values are for a conservative RNP. The gain for polarization diversity in rural areas has been examined in [2.3]. Diversity gain Environment dense urban+urban + suburban

rural, highway

Space diversity

Polarization diversity

same order of magnitude Horiz separ.: 3..6 dB 3..6 dB, dep. on UL wave propag. condition Vert. separ: 3..4.5 dB (LOS, NLOS, …), MS antenna inclination Horiz separ.: 5 dB negligible 0-0.6 dB Vert. separ: 3 dB

Table 23: Summary on diversity gain for space and polarization diversity in different environments for GSM900/1800 Remarks: 1. The values of Table 23 are valid for maximum ratio combining (MRC) method used in the Alcatel G3 TRX. For the G4 TRE, and for B6.2 BSS software release onwards, a new combining method (Enhanced diversity combining, see APPENDIX E ) offers additional antenna diversity gain vs. the MRC method. According to [7.1], currently there are only simulated values available for the antenna diversity gain of the enhanced diversity combining method vs. no combining (the values are independent on the penetration rate of BTS using enhanced diversity): •

In interference limited environment (dense urban, urban): 2-5 dB improvement.

•

In noise limited environment (suburban/residential, rural): 3-6 dB improvement;

As long as the simulated values are not confirmed by extensive field tests, it is recommended to consider the values of Table 23. Impact on RNP of enhanced diversity combining: •

No changes on existing antennas and supporting constructions;

•

Improved Rxqual in UL direction only;

•

The additional gain of the enhanced diversity combining can only be applied if the mobile and the interfering MS are located in different direction from the BTS: this happens typically e.g. a.) in random hopping scenarios or b.) in indoor scenarios where it is desired to reduce the uplink interfering signals coming from an outdoor micro cell for a mobile in indoor environment connected to a G4 TRE.

2. For urban and suburban environment the diversity gain has the same order of magnitude. 3. For rural environment polarization diversity gain is negligible (in LOS areas there are no reflection, diffraction effects which are responsible for polarization direction changes). 4. The diversity gain of Table 23 is considered only in the UL path of the link budget. 5. Modeling of diversity gain in A955 RNP tool: no impact on predictions, independent if MRC or enhanced diversity combining method is active, since there is no UL prediction in A955; furthermore, the UL path is further improved through antenna diversity. 26/64

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Rx Diversity gain GSM900/1800

Rx Diversity gain UMTS –FDD

In an UMTS system, the RX diversity gain depends on the service, on the multipath profile and on the velocity. The Rx diversity gain is manifested by a reduction of the required received uplink Eb/No.


A typical RX diversity gain on Rx Eb/N0 is between 1.5 and 4 dB; it is slightly larger in Pedestrian A than in Vehicular A environment since the channel power variations are larger and the interchip interference is lower in Pedestrian A. This is shown exemplarily in Table 24 by simulation results for an 8 kbit/s voice channel simulation results for different services (provided by TD/SYT). The simulation assumption was that the two RX signals were completely uncorrelated, i.e. it can be expected that in high scatter environments (urban, suburban) the same order of magnitude can be achieved with space and cross polar diversity. Environment

Speed (km/h) 3 6 10 25 50 120 200 350 3 6 10 25 50 120

Vehicular A

Pedestrian A

1 antenna 7.7 7.9 8.0 8.1 8.3 8.9 9.5 11.1 7.2 7.7 7.8 8.2 8.6 9.1

Uplink 2 antennas 5.1 5.2 5.3 5.4 5.5 6.3 7.0 8.5 4.2 4.8 4.7 4.8 5.0 5.8

Rx Div. Gain 2.6 2.7 2.7 2.7 2.8 2.6 2.5 2.6 3.0 2.9 3.1 3.4 3.6 3.3

Table 24: Rx Eb/N0 required for a BER of 10-3 in speech 8 kbps and corresponding Rx diversity gain for UMTS-FDD 2.7.2 Rx space diversity Required Rx antenna separation for space diversity

There are 2 driving factors for the required Rx antenna separation in case of space diversity:

Separation to achieve sufficient signal decorrelation

?

Separation to achieve sufficient signal decorrelation;

?

Separation due to effective antenna height.

The recommended and required separation between the two Rx antennas to achieve sufficient signal decorrelation and so the space div. gain given in Table 23, Table 24 is: d H=20λ, dV =15λ

Table 25 gives the corresponding values (λ ≈ 33/16/14.6 cm for GSM900/GSM1800/UMTS-FDD frequency ranges). Rx antenna separation horizontal vertical

GSM900 6.6 m 5m

frequency band GSM1800 UMTS-FDD 3.2 m 2.9 m 2.4 m 2.2 m

Table 25: Recommended Rx antenna separation for space diversity Remark: the vertical separation is measured between the antenna radomes (i.e. between the bottom of upper and the top of lower mounted antenna). Rules: 1. 3DF 01902 2711 VAZZA

For space diversity prefer horizontal separation vs. vertical separation, due to

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higher diversity gain

•

lower mast/pole heights.

On the other hand in case of flat roof mounting of antennas, the number of poles possibly increases (due to 2 poles per sector diversity, but with common usage of poles for adjacent sectors) . 2.

If the installation space is limited, lower separations than dH=20λ, dV =15λ can be applied, at the cost of a lower diversity gain, but they should not be reduced below 50% of the values in Table 25. There is no deterministic formula to calculate the diversity gain as function of separation distance, because the gain is highly dependent on the multipath environment. But a lower diversity gain due to lower separations than dH=20λ, dV =15λ has only an effect, if the system is UL limited. It needs to be checked with a linkbudget for the installed equipment, if there will be an impact on the cell range in UL (see also Table 14, Table 15).

Separation due to effective antenna height

The required (horizontal) antenna spacing is not only determined by Table 25, but additionally by Equation 3: d > effective antenna height/10 Equation 3: Space diversity separation as function of effective antenna height

dH

where the effective antenna height takes into consideration the topography as shown in Figure 6. Both conditions need to be fulfilled; the highest separation is valid.

BTS heff = f ( α,D1, hBTS, hMS )

BTS

MS heff

hMS

The rule comes into account only for e.g. antennas placed on a 20 m tower on a high hill serving the valley below, where the effective antenna height can easily trespass 60 m, e.g. 100 m. The dH for optimum space diversity gain should be 10m, but this is irealistic to implement. So it is not relevant whether the implemented spacing is 6m or less, since the diversity gain given in Table 23 is never reached and will be low. Figure 6: Effective antenna height

D1

Dual band, triple band Dual band resp. triple band cases with Rx space diversity: ?

Single band antenna usage: for required Rx antenna separation refer to Table 25.

?

Dual band resp. triple band antenna usage: the required Rx antenna separation is determined by the lower band requirements in Table 25.

2.7.3 Polarization diversity The main issues of cross polar antennas application are:

Rx application of cross polar antennas in GSM, UMTS

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?

only Rx application

?

Tx+Rx application

?

cross polar vs. horiz./vert. polarized antennas

The main issue for the Rx application is the Diversity gain in UL (cf. [2.2], [2.3]):

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•


Tx+Rx application of cross polar antennas in GSM

?

The Rx diversity gain improves only the UL path of the link budget. For achievable values, see Table 23 and Table 24.

?

In rural (low scatter) environment, Rx polarization diversity gain is negligible for GSM and UMTS.

The following considerations are valid for GSM and need to be verified for UMTS. The main issues for the Rx application are the same as above. The main issues for the Tx application are:

1. Additional pathloss for DL Pathloss differences between scenarios with cross polarized transmitting antennas and vertical polarized ones depend on propagation conditions (LOS or NLOS, scattering, MS antenna inclination) in the current environment. [2.3] examines the dependency for GSM ( 900,1800). In high scatter NLOS areas, the polarization of the received wave fronts is independent from the polarization of the source antenna and randomly distributed around 360O (cf. [2.2]). This means, that the polarization of the receiving antenna has no impact on the pathloss, so that vertical and cross polarized transmitting antennas lead to the same pathloss result, no matter of which polarization is the receiving antenna. The additional pathloss for the Tx path (DL) in urban/suburban environment for cross polarized antennas vs. vertical polarized antennas, is ≈0.6 dB, so nearly 0. In contrary, for a LOS condition, the additional measured pathloss is considerable (up to 4.3 dB) if the polarizations of transmitting and receiving antenna do not match. Rule of thumb for RNP: for GSM in rural areas, the mean additional loss compared to vertical polarization is in the range of 1.5 to 3 dB. 2.

Air combining gain for DL

For air combining principle see APPENDIX F . Air combining is recommended if no heavy visual impact is to fear, as in e.g. rural areas/highways. With air combining, combiner losses can be saved, resulting in a lower path loss of ˜ 3 dB/saved combiner stage independent on frequency range. To be more accurately on the air combining gain: according to [7.7] the air combining gain isn’t entered anymore directly in the link budget (the former definition of the BTS transmit output power was based on the internal TRE output power e.g. 35 W, from which duplexer, combiner and internal cabling losses were subtracted); instead, the new definition of the BTS output power specified at the antenna connector already considers/omits duplexer, combiner and internal cabling losses. Handling of cross polar antennas in RNP tools 1.

Consideration of the additional pathloss in the A955 RNP tool

For the prediction calculations of A955, only the transmitting aspect is relevant. It is assumed that in this case, the receiving antenna (the MS antenna) is vertical polarized. (However the fact, that in reality a high percentage of receiving MS antennas are inclined is not considered in A955). An additional pathloss is currently not automatically considered in A955 V5/V6, since the tool has no information about polarization planes. Workaround: RNE can manually subtract this pathloss from the EIRP for rural regions. 2.

Consideration of the air combining gain in the A955 RNP tool

The treatment of the combining gain for A955 RNP tool can be considered by using the new specified value of the BTS output power at the antenna connector which already omits duplexer, combiner and internal cabling losses. 3. 3DF 01902 2711 VAZZA

Cross polar antenna pattern modeling in RNP tools

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?

has no information about polarization planes;

?

can consider only one of the antenna diagrams, i.e it assumes the same relative antenna gain and though predicts the same pathloss for the DL and UL spectrum portions of the same frequency band.

Example: a broadband crosspolar antenna for GSM 1800/UMTS with variable electrical downtilt (0°-8°) has 20 patterns specified by the manufacturer: for each of the 5 downtilt values (0°, 2°, 4°, 6°, 8°), 4 antenna patterns are given (for UL band in +45° polarization plane , UL –45°, DL +45°, DL –45°). Preprocessing yields one antenna pattern for each considered downtilt value and it typically involves the following steps:

Cross polar vs. horiz./vert. polarized antennas

?

conversion of the dB pattern values into W

?

averaging the W values for UL+45°, UL –45°, DL +45°, DL –45°

?

conversion of W values back into dB.

Cross polar antennas have the same polarization diversity gain compared to horiz./vert. polarized antennas. Still, cross polar antennas are preferred instead of horiz./vert. polarized antennas because: in case of air combining, both polarization directions of a cross polar antenna can be used for Tx, whereas only the vertical polarization direction of a horiz./vert. polarized antenna can be used for Tx ([2.3] shows that important losses can also be expected on the horizontal polarization direction, assuming a vertical polarized MS antenna). Air combining with horiz./vert. polarized antennas is not practicable; so, horiz./vert. polarized antennas have a low market penetration. In this document, the focus within dual polarized antenna class will be only on cross polar antennas and not on horiz./vert. polarized antennas.

2.7.4 GSM space and polarization diversity on UL An interesting combination of space and polarization diversity is given in Figure 7. Ant. A

Ant. B

D

ANC 1

ANC 2

TRX1 TRX2

TRX3 TRX4

Figure 7: GSM 4-RX diversity on UL It is not a 4-Rx diversity, since for a given call only 2 reception paths are present. For the separation D, Table 25 applies. The gain benefit of this mixed diversity configuration is expected to be higher than the one indicated in Table 22 (to be confirmed on field tests. 2.7.5 Further rules on diversity Selection space vs. polarization diversity for GSM900/1800

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For the Rx application the selection between space and polarization diversity is based on the diversity gain, according to ch. 2.7.1:

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Some antenna manufacturers provide antenna patterns for different spectrum portions in the same band (e.g. for UL/DL) and for different polarizations (+45° / – 45°; they result from co-polar measurements, i.e. Tx and measuring Rx antenna have the same polarization). In the main beam direction the patterns are typically very similar, but in the side lobes differences of = 20 dB are possible. Since RNP tools generally (and A955 particularly) cannot handle more than one (horiz. and vert.) antenna pattern, the different pattern data has to be preprocessed by the planner. A955 V5/V6 currently:


Selection space vs. polarization diversity for UMTS-FDD Compatibility of downtilt and diversity Rx antenna orientation in space diversity

?

For dense urban, urban and suburban areas crosspolar antennas are recommended.

?

For rural areas and highway coverage in a tyypical coverage driven planning, the space diversity (with vertical polarized antennas) is recommended. For the exceptional case of a traffic driven planning in these environments, crosspolar antennas can be considered to minimize project logistic.

Cross polar antennas must be used in urban and suburban areas, whereas two separated vertical polarized antennas must be used in rural areas for space diversity. Space and cross polar diversity are compatible with mechanical and electrical downtilt; but in general electrical downtilt is preferred vs. mechanical downtilt (see ch. 2.6), especially in UMTS (interference limited system). The orientation of the Rx diversity antenna arrangement must correspond to the cell orientation (see Figure 8), to achieve highest space diversity gains (cf. [10]) RxA

Maximum Diversity

Maximum Diversity RxA

RxB

Cell Border

Correct orientation Figure 8: Orientation of Rx antennas for space diversity

RxB

Incorrect orientation

2.7.6 UMTS-FDD Tx diversity In this chapter only the expected gain due to STTD and closed loop mode 1 is given. Further details on UMTS-FDD Tx diversity are provided in APPENDIX E and [6.1]. Simulation results on Tx diversity gain for different services are provided by TD/SYT in [6.2]. Tx diversity gain

The Tx diversity gain provided by Tx diversity in DL is manifested by 2 effects: ?

a reduction of the required Tx DL Eb /N0.

?

a reduction of the required Rx DL Eb /N0 .

For Tx Eb /N0 and Rx Eb /N0, the denominator N0 denotes the noise measured at the receiver side and Eb is the energy per information bit at the transmitter side and receiver side respectively. Table 26 exemplary shows Tx DL Eb /N0 required for a target BLER=10-2 (AMR 12.2 kbps) and the corresponding Tx diversity gain for STTD/ Closed loop mode 1 for the 3GPP defined multipath environments Vehicular A (representative for macrocellular propagation) and Pedestrian A (microcellular propagation). Some remarks on the TD/SYT simulation results:

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STTD always improves the performance compared to no transmit diversity. The largest gain is obtained for low speed and environment with low multi-path diversity such as rural or indoor environments (3.3 dB in Pedestrian A environment at 3 km/h). The gain then rapidly decreases when the speed increases.

?

Closed loop mode 1 improves the performance compared to no transmit diversity only for low mobile speeds (typically below 60-80 km/h) and degrades them otherwise. The largest gain is obtained for low speed and environment with low multi-path diversity like with STTD (4 dB in Pedestrian A environment at 3 km/h).

?

Comparison STTD/Closed loop mode 1: the closed-loop mode 1 enables better performance (higher capacity gain) than STTD for low mobile speeds (below 50-60 km/h). For larger mobile speeds (above 50-60 km/h), STTD enables better performance.

?

A big advantage of STTD over closed-loop mode 1 is that STTD is always better than no transmit diversity, which is not the case of closed-loop mode 1. Indeed, closed-loop mode 1 degrades the performance compared to no transmit diversity

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for medium and large mobile speeds (above 60-80 km/h) with a loss that may be significant (up to 1.1 dB at 120 km/h and even larger loss above 120 km/h).

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Speed (km/h)


Environment

3 6 10 25 50 120 250 350 3 6 10 25 50 80 120

Vehicular A

Pedestrian A

DL Target transmit Eb /N0 Without STTD ClosedTx loop diversity mode 1 7.4 6.7 6.2 7.7 7.4 7.0 6.6 6.8 8.1 10.1 11.3 11.1 10.8 8.9 8.0 7.9 7.9

6.8 6.7 6.6 6.3 6.6 8.1 10.1 8.0 8.0 8.3 7.2 7.1 7.0 7.0

Tx diversity gain STTD Closedloop mode 1 0.7 1.2

6.3 6.3 6.1 6.4 7.9 9.6 14.3 7.3 7.3 7.2 6.8 6.5 7.8 8.6

0.9 0.7 0.4 0.3 0.2 0 0 3.3 3.1 2.5 1.7 0.9 0.9 0.9

1.4 1.1 0.9 0.2 -1.1 -1.5 -4.0 4.0 3.8 3.6 2.1 1.5 0.1 -0.7

Table 26: Target Tx DL Eb/N0 and corresponding Tx diversity gain for UMTS-FDD for a target BLER = 10-2 (AMR 12.2 kbps) Table 28 shows Rx DL Eb /N0 required for a BER of 10-3 in speech 8 kbps and the corresponding Tx diversity gain for STTD in the multipath environments Vehicular A and Pedestrian A (simulation results provided by TD/SYT): ?

Only a slight reduction is achieved (= 1 dB).

?

The Tx diversity gain on Rx Eb /N0 is larger for Pedestrian A than for Vehicular A.

Environment

Speed [km/h]

Vehicular A

3

Downlink Eb/No Eb/No without Tx STTD diversity[dB] [dB] 6.8 6.6

Tx div. gain [dB]

0.2

6 7.1 6.9 0.2 10 7.2 7.0 0.2 25 7.2 6.9 0.3 50 7.4 7.1 0.3 120 7.6 7.5 0.1 200 8.4 8.2 0.2 350 10.4 10.0 0.4 Pedestrian A 3 6.5 6.3 0.2 6 7.1 6.6 0.5 10 7.6 6.9 0.7 25 8 7.0 1 50 8.3 7.3 1 120 8.5 7.7 0.8 Table 27: Rx DL Eb/N0 required for a BER of 10-3 in speech 8 kbps and corresponding Tx diversity gain for UMTS-FDD

Impact on antenna engineering 1. For Tx diversity the 2 Tx paths need to be uncorrelated; this is achieved by:

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space diversity: for the separation rules refer to chapter 2.7.2 and Table 25;

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polarization diversity.

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2. With duplexer usage, each Rx diversity antenna can also be used for transmission with Tx diversity. 3. TX diversity gain variation in urban and rural environment: to be studied on field.

2.7.7 UMTS FDD 4-RX diversity on UL Diversity gain

The gain of 4-RxDiv can be mapped onto a gain in cell range only in case of limited UL in the link budget. If the system is DL limited, 4RxDiv will show no effect on the cell range (cf. [6.3]). The diversity gain is manifested by a reduction of the required Rx UL Eb/No which will improve the coverage and capacity performance of the system. The potential gain of receive antenna diversity with 2, 3 or 4 perfectly uncorrelated antennas is simulated by TD/SYT for vehicular A and pedestrian A environments, where the BER is measured at the output of the channel decoder ([6.3]). For a BER of 10-3 there is a difference on Rx Eb/No level in the node B of: ?

˜ 3 dB between using 1 or 2 receiving antennas;

?

˜ 2 dB dB between using 2 or 4 receiving antennas.

The real potential gain of 4-RxDiv will depend on the environment (propagation channel), the service (BER or BLER), the speed of the mobile and antenna characteristics. Implementation

4-Rx diversity for UMTS-FDD is provided optionally only in the Node B. To achieve these gains the decorrelation of the Rx branches must be ensured by space diversity or polarization diversity. ?

For space diversity, this decorrelation can be achieved by spatially separating the antennas, horizontally or vertically, by applying the separation rules of Table 25 and Equation 3.

?

For polarization diversity, the decorrelation is obtained with cross polar antennas (+/-45°).

Upgrade towards 4Rxdiv The upgrade strategy towards 4Rxdiv depends on the previously implemented 2Rxdiv antenna solution. Upgrade starting from space diversity ?

Initial situation: 2RX diversity scheme with single polarized antennas and vertical or horizontal separation.

?

After upgrade: for low visual impact, replacement of the 2 existing antennas with 2 cross polar antennas, see Figure 9. Space Diversity

Vertical polarised antenna 1

Distance d

Rxdiv1

Vertical polarised antenna 2

Replace Antennas

Polarisation Space Diversity Diversity Xpol antenna 1

Distance d

Rxdiv1 Rxdiv2

Rxdiv2

Polarisation Diversity Xpol antenna 2

Rxdiv3 Rxdiv4

Figure 9: 4-Rx div upgrade starting from space diversity Upgrade starting from polarization diversity ?

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Initial situation: 2RX diversity scheme with 1 cross polar antenna (typical in dense urban, urban, suburban environment).

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4. Consideration of TX diversity gain in A955 RNP prediction: use Eb/No of Table 26.

After upgrade: combination of space and polarization diversity; adding of an additional cross polarized antenna, either vertically or horizontally separated from the first one; the separation rules of Table 25 and Equation 3 must be respected; higher visual impact; see Figure 10.


?

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Xpol antenna

Rxdiv3

add Xpol antenna in distance d

Polarisation Space Diversity Diversity Xpol antenna 1

Distance d

Rxdiv1 Rxdiv2

Rxdiv4

Polarisation Diversity Xpol antenna 2

Rxdiv3

Rxdiv4

Figure 10: 4-Rx div upgrade starting from polarization diversity

2.8 Intra-system and inter-system compatibility assessment for site sharing Mobile intra-system and inter-system compatibility for the same site have an impact on antenna engineering of this site. This chapter describes the methodology for compatibility analysis and shows how to achieve the compatibility. For related documentation to this topic see [5.1]. EMC aspects

The possible interference scenarios and most important EMC interference mechanisms (Transmitter Noise/Spurious Emissions , Blocking, Intermodulation) need to be combated to guarantee the intra-system and inter-system compatibility for site sharing/co-location. They are described in APPENDIX H .

Methodology

The assessment methodology for mobile intra-system and inter-system compatibility for site sharing (co-siting) consists in the following steps (for GSM and UMTS): 1. Listing of possible relevant intra- and inter-system incompatibility issues. example: for a site which is shared by operator1 (which operates in 900/1800 dual band) and operator2 (which operates UMTS) the possible system incompatibility issues are: a.) intra-system incompatibility inside 900, 1800, UMTS b.) inter-system incompatibility between 900-UMTS, 1800-UMTS, 900-1800. 2. For the cases identified in step 1: •

Analysis of the 3 EMC interference mechanisms by considering: •

the requirements specified by the relevant standardization body (e.g. 3GPP for GSM and UMTS) for: level of spurious emissions, level of blocking limit, in-band IM attenuation etc.

•

the Alcatel values for: level of allowed spurious emissions, level of limiting interference signal (for spurious emissions), level of allowed blocking limit, allowed IM level etc. (In order to prevent performance degradation for co-located mobile systems, the BTS hardware of the vendor needs to fulfill the requirements specified by the relevant standardization body.)

•

Determination of the resulting decoupling requirements for each of the 3 EMC interference mechanisms.

•

Finding out which decoupling values are the dimensioning ones (see Table 28, Table 29 for some important combinations).

3. Planning how to implement the decoupling. For exemplary calculations see [5.1]. Tx/Rx decoupling requirements

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Definition: The decoupling (isolation) is measured between the antenna connectors of the transmitter in mobile system 1 and of the receiver in mobile system 2, as shown in Figure 11. The achievable decoupling value is strongly influenced by:

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Polarisation Diversity

Antenna

Antenna

TX power


Decoupling

Rx BTS or Node B

?

the antenna spacing between Tx antenna (of mobile system 1) and Rx antenna (of mobile system 2),

?

the gains and radiation patterns of the 2 antennas,

?

the presence of filters and diplexers. Figure 11: Definition of required decoupling

Tx BTS or Node B

Alcatel proposes in Table 28 (cf. [5.1]) the Tx/Rx decoupling requirements for intraband and some important inter-band mobile system co-locations, both for Alcatel BTS and other vendors BTS (also fulfilling the mentioned 3GPP specifications); Table 28 also mentions the interference mechanism which is the dimensioning one. GSM900 (RX) Specification according to:

GSM 05.05

GSM 05.05

Alcatel

25 dB

GSM1800 (RX) GSM 05.05

Alcatel

3G TS 25.104

Alcatel

46 dB

25 dB IM

v.8.5.1: 34dB

v.8.5.1: 34dB

GSM spurious

GSM spurious

Blocking

GSM900 (TX) →

IM Alcatel

25 dB

46 dB Blocking

25 dB IM

IM GSM 05.05

39 dB Blocking

GSM1800 (TX) →

Alcatel

39 dB Blocking

3G TS 25.104 UMTS (TX) →

Alcatel

35 dB

Blocking

35 dB

Blocking

25 dB IM

25 dB IM

25 dB IM 30 dB

Blocking

30 dB

Blocking

UMTS (RX)

25 dB IM 43 dB Blocking

43 dB Blocking

30 dB

Blocking

30 dB

Blocking

61 dB Blocking

30 dB

Blocking

v.8.4.1: 85 dB

v.8.4.1: 85 dB

v8.5.1: 34dB

v8.5.1: 34dB

GSM spurious

GSM spurious

62 dB

34 dB

Blocking

GSM spurious

58 dB

Blocking

58 dB

Blocking

34 dB

Spurious

34 dB

Spurious

Table 28: Tx/Rx decoupling requirements for some important system co-locations Remark: the requirements specified by 3GPP are based on the assumption that the decoupling (between the Tx antenna connector of mobile system 1 and the Rx antenna connector of mobile system 2, as shown in Figure 11) provided by the antenna system is minimum 30 dB; this assumption is indeed confirmed by antenna manufacturer measurement series, refer to [RFS 1]. But by using the Alcatel EVOLIUM™ 9100 BTS (G3, G3.5, G3.8, G4, G4.2, Evolution step 1, Evolution step 2), even less decoupling is required than the 30 dB of Table 28:

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?

For certain combinations 900 TX-900 RX, 1800 TX-1800 RX, 900 TX-1800 RX, 1800 TX-900 RX: 25 dB are sufficient (IM is the dimensioning scenario; Transmitter Noise/Spurious Emissions: no problem, due to high selectivity of Tx filter as specified by 3GPP for GSM; Out-of-band blocking: no problem, due to the high selectivity of the Rx filters).

?

For other combinations, the 30 dB in Table 28 provide additional safety margin, since the required decoupling is also less than 30dB due to relaxed receiver blocking requirement (derived from [5.1]), see Table 29.

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2.8.1 How to ensure the intra-system and inter-system compatibility? This chapter gives engineering hints on how to achieve the sufficient decoupling for intra-system and inter-system compatibility. The decoupling to combat the 3 interference mechanisms is achieved by space separation, filters, diplexers and duplexers. Additionally for IM a careful frequency planning is required. Space separation

For the intra-system case it is possible to apply the empirical formulas below (source: Celwave/RFS) giving an orientative value for the decoupling; they are applicable: ?

for calculation of the decoupling/isolation between Tx/Rx antennas of •

the same sector;

•

adjacent sectors;

•

co-sited adjacent operators;

?

for in-band case in GSM and UMTS bands;

?

for omni and directional antennas;

?

for vertical polarized Tx/Rx antennas ;

?

for 0° mechanical tilt.

The distance required for a specific isolation varies with operational frequency and antenna gain. Lower frequencies and higher gains require greater separations. 1. Achievable decoupling/isolation DV by vertical separation DV=28+40log(dV/λ) [dB] Equation 4: Decoupling by vertical separation

Tx dv

Mast

dV = vertical separation as indicated in the sketch λ = wavelength (GSM900 ≈ 33 cm, GSM1800 ≈ 16 cm; UMTS-FSS ≈ 14.6 cm)

Rx

This formula is only valid for dV/λ > 10

dm

For optimum distance dm to the mast/wall, see ch. 3.1. 2.) Achievable decoupling/isolation DH by horizontal separation

Tx

dH

DH=22+20log(dH/λ)-(GT(ϕ)+GR(ϕ)) [dB] Equation 5: Decoupling by horizontal separation

Rx

This formula is only valid for dH /λ > 10 G T and G R are gains (T=transmit; R=receive) measured on the horizontal antenna diagrams of the Tx and Rx antennas in the direction (angle ϕ) of the imaginary “antenna connection line”, i.e. = (gain in main beam direction – relative gain in direction ϕ) 3.) Achievable decoupling D by combination of horizontal and vertical separation Tx

α dV

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D=(DV-DH)α/90°+DH [dB] (no tilt considered ) Equation 6: Decoupling by of horizontal+vertical separation separation

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required decoupling 900 Tx-UMTS Rx 21 dB UMTS Tx-900 Rx 18 dB UMTS Tx-UMTS Rx 13 dB Table 29: Tx/Rx decoupling requirements for Alcatel BTS co-location in some important systems

This is a linear interpolation of the 2 formulas above. Remarks to the decoupling Equation 4, Equation 5, Equation 6 : All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

1. Since the formulas given are not exact and have several restrictions, it is recommended to carry out decoupling measurements locally on the site to verify the compliance with the requirements. This is the more recommended in the cases: •

the separation distances yielded by the mentioned formulas, are too high and not feasible for the network operator (from financial, visual, civil engineering/site construction etc. p.o.v.);

•

mechanical downtilt application;

•

cross polar Tx/Rx antenna usage;

•

inter-system co-siting with substantially different frequency band (e.g. GSM1800-UMTS).

2. In case of spatial Tx/Rx separation with dual band / triple band antennas, the decoupling values of the lowest frequency band are dimensioning. E.g. for GSM900/1800, the isolation has to be calculated for the 900MHz band, since the decoupling for horizontal separation is 6 dB lower than in 1800MHz and for vertical separation 12 dB lower than in 1800MHz (Figure 12). Figure 12 shows the achievable decoupling based on horizontal (for a 11dBi omni antenna) and vertical separation according to equation given above. 110 105

35 30

GSM 900 GSM 1800

25 20

Decoupling Dv [dB]

100 95 90 GSM 900

85

GSM 1800

80 75 70 65

15

9

9 10

10

8

8

7

7

6

6

5

5

4

4

3

1

2

3

60

1

2

Decoupling Dh (dB)

40

vertical separation [m]

Horizontal separation (m)

Figure 12:Decoupling achieved by horizontal and vertical separation Antenna spacing for the Evolium A9100 BTS (G3 /G4) with antenna diversity

In Figure 13, the antenna separation dH and dV between Ant A and Ant B is dH and dV := max { X, Y} where X=space diversity separation cf. Table 24 between RxA-RxdivA, RxB-RxdivB

Y=decoupling separation cf. Equation 4, Equation 5, Equation 6 between TxA-RxB, TxA-RxdivA, TxB-RxA, TxB-RxdivB. Figure 13: Antenna spacing for the Evolium A9100 BTS (G3 /G4) with antenna diversity TxA, RxA, RxdivB

TxA, RxA, RxdivB

Ant A

TxB, RxB, RxdivA

dV

dH Ant B

Ant A

TxB, RxB, RxdivA ANC

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For the Evolium A9100 BTS (G3 /G4) with antenna diversity, the decoupling requirement is easier fulfilled with a vertical separation of antennas (horizontal spacing distances may not be feasible in practice). This is valid for omni and directional antennas, and for any frequency range. But this must be balanced against the fact that the diversity gain for vertical separation is ˜ 2 dB lower than for horizontal separation (see Table 22, Table 23). Examples for space separation Example 1: Low-loss configuration for more then 2 TRXs per sector Ant. C

Ant. A

Ant. B

Ant. C

Ant. D

Ant. D

D1

D2 D1

D2

D1 Ant. A

Ant. B D1

ANC 1

ANC 2 ANC 1

TRX1 TRX2

ANC 2

TRX3 TRX4 TRX1 TRX2

solution 1

TRX3 TRX4

solution 2

Figure 14: Separation for low-loss configuration for more then 2 TRXs per sector Given is a low-loss configuration Evolium A9100 BTS (G4) with 4 TRX’s/sector (e.g. for rural areas in GSM1800) and directional vertical polarized antennas of Celwave series AP 186516 (65° horiz. HPBW, 7.5° vert. HPBW, 17 dBi gain) see Figure 14. The issues are: ?

Tx/Rx antenna spacing inside the same sector: D1, D2=?

?

Tx/Rx antenna spacing between adjacent sectors (of the same operator) D3 =?

D1 (between the antennas of the same ANc, i.e. A-B and C-D) The distance D1 is determined by the diversity spacing requirement of Table 25. Here it is recommended to choose horizontal separation (if site installation space is not limited) to achieve higher diversity gain (see Table 23). With vertical separation site construction is simplified however the required separations can also lead to high towers. D2 (between the antennas of the 2 ANc’ s of the same sector, i.e. A-C, A-D, B-C, B-D) Two solutions are possible as indicated. The distance D2 is determined by the minimum decoupling requirement of the Evolium BTS to prevent from IM which is min. 25 dB between TX and RX paths (Table 28). The formulas in 2.8.1 can be used only for calculation of the theoretical decoupling for d/λ>10, yield: D2 (solution 2) << D2 (solution 1) and are not practicable.

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Rule:


Practically, decoupling measurements done locally on the site by RFS/Celwave (cf. [RFS 1]), typically yield for GSM1800 antennas of series AP 186516 a minimum isolation of: ?

30 dB, at 0 cm horiz. antenna separation (i.e. A+C, B+D may almost touch)

?

60 dB, at 0 cm vertical separation Seen from this p.o.v., solutions 1 and 2 are equally recommended.

D3 (between the antennas of the two ANc’ s of adjacent sectors) The distance D3 must respect the same requirement as D2. So, for the typical case of a 3 sector site with equal 120° sector arrangement (i.e. sites, where the antennas of the sectors point in different directions and installation space on the site is sufficient to avoid crossing of antenna main beams) the antennas of the adjacent sectors may almost touch each other (decoupling measurements cf. [RFS 1] typically yield a minimum isolation of 30 dB at 0 cm horiz. antenna separation). Example 2: similar to example 1, but antennas A+B, C+D are each replaced by one GSM1800 cross polar antenna of Celwave series APX 186515 (65° horiz. HPBW, 7 ° vert. HPBW, 17.5 dBi gain). (Remark: lets consider this although it is better to use space diversity in rural areas) D1 – not applicable in this case D2 – similar considerations as in example 1 ?

For calculation of the theoretical decoupling, the formulas in 2.8.1 are not applicable.

?

Practically, decoupling measurements cf. [RFS 1] yield for cross polar antenna of the type APX 186515 (65° horiz. HPBW, 7 ° vert. HPBW, 17.5 dBi gain) and APX 186516 (65° horiz. HPBW, 4.5 ° vert. HPBW, 18.3 dBi gain) a minimum isolation of •

45 dB (worst case for co-polar or cross-polar measurement), at 0 cm horizontal antenna separation

•

55 dB (worst case for co-polar or cross-polar measurement), at 20 cm vertical antenna separation

Seen from this p.o.v., solutions 1 and 2 are equally recommended. D3 – similar considerations as in example 1 Decoupling measurements for type APX 186515 (resp. APX 186516) cf. [RFS 1], typically yield a minimum isolation of 30 dB at 0 cm horiz. antenna separation (worst case for co-polar or cross-polar measurement) Example 3: similar to example 1, but for GSM900 same conclusions as in example 1. Example 4: similar to example 1, but for dualband sites GSM900/GSM1800 Given is a dualband Evolium A9100 BTS (G4) configuration with 2 TRX’s/GSM900 + 2 TRX’s/GSM1800. For each frequency band the chosen antennas are directional, single band, vertical polarized antennas (let’s assume that the operator preferred single band antennas for flexible tilt tuning and antenna space diversity for rural area) ?

for GSM 900 Celwave AP 909014 (90° horiz. HPBW, 8.5° vert. HPBW, 16 dBi)

?

for GSM 1800 Celwave AP 189014 (90° horiz. HPBW, 7.5° vert. HPBW, 16.1 dBi)

Same considerations apply as in example 1. D1- will be different for GSM900 and GSM1800 D2- decoupling measurements for vertical polarized antennas will typically yield a minimum isolation of

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?

30 dB (in GSM900) and 32 dB (in GSM1800), at 0 cm horizontal antenna separation

?

40 dB (in GSM900) and 52 dB (in GSM1800), at 0 cm vertical separation

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D3- Same considerations as in example 2.

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2.9 EMC impact on antenna system planning All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

When a site needs some re-engineering to respect the exposure index in a neighbour living place (mainly fixed by local authorities), the most straightforward solution is to change the height, the tilt or the EIRP. These modifications will then impact the coverage and frequency reuse in neighbour cells. This chapter anticipates how Alcatel would implement these changes and what would be the actual impact on dense urban and urban environments. Reason: the exposure index requirement has not been finally settled for the time being. Option 1: if site re-engineering is not desired/allowed/possible, the certain distances must be respected to fulfil the exposure index requirement. Option 2: site re-engineering by increasing only the antenna height Advantage: the coverage gets better (this may not necessarily be an advantage if the coverage was sufficient before the modification) Drawbacks: ?

risk to increase the interference (if no additional downtilt can be applied)

?

limitation on antenna mast height may apply

?

critical/not feasible in case of mast sharing with competitor operator

Option 3: site re-engineering by decreasing only the antenna downtilt Drawbacks: ?

close to the site, it is almost impossible to reduce the exposure index to the required limit even with 0° downtilt

?

far from the site, the interference risk is increased (especially in 1x1 RFH networks)

Option 4: site re-engineering by reducing only the EIRP of the BTS

Consequences: ?

undermining the benefit of high power TRX in MAPL

?

less coverage and increased number of sites

Option 5 (most probable): site re-engineering by mixed solution, i.e antenna height increase + downtilt increase + EIRP reduction

2.10 RNP tool related aspects on antenna planning This chapter summarizes the handling of the antenna system planning aspects which are relevant from point of view of RNP tool (e.g. A955) handling. These are:

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?

filling of the vertical antenna pattern outside the main beam; necessary in order to approach the prediction to the measurements; currently this topic is under investigation in PCS

?

planning for a maximum antenna height, see chapter 2.4 ;

?

consideration of vertical patterns with an electrical tilt, see chapter 2.6;

?

handling of crosspolar antenna patterns, see chapter 2.7;

?

respecting the exposure limit in a specified distance from the antenna to the next building/housing apartment in main beam direction, see chapter 2.9

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3 RULES FOR ANTENNA INSTALLATION

3.1 Mounting rules for tower, mast, roof, wall mounting of antennas This chapter gives mounting rules for omni, sector, macro and micro antennas for common mounting places; this comprises mainly clearance rules such as: ?

minimum mount distance of omni antennas from supporting structure, see 3.1.1

?

minimum mounting height of antennas (see 3.1.2)

?

maximum skewing angle for antennas relative to a reflective surface (see 3.1.3).

The considerations below are generally valid for GSM and UMTS. Further details are contained in APPENDIX G . Table 30 gives a summary on the required standard mounting restrictions. If the rules cannot be respected, site operation is still possible but with QoS results worse as predicted. Macro antennas

Tower Mast Roof top

µ antennas

Mounting on top side top side wall (e.g. elevator shaft) mast - top mast - side

Wall

Omni NR, remark 1 see 3.1.1 NR, remark 1 see 3.1.1 n.a. see 3.1.2 see 3.1.1, 3.1.2 see 3.1.4

Sector (remark 2) n.a. see 3.1.3 n.a. NR see 3.1.2,3.1.3 n.a. see 3.1.2 see 3.1.4

Table 30: Summary on required mounting restrictions (NR=no restriction; n.a.= not applicable) Remarks to Table 30: 1. For top mounting of omni antennas on tower /mast (nowadays rarely done) : no mounting restrictions apply if there are no further obstacles in the near field range, except the lightning protection. An almost circular pattern is created (with some tolerable ripples in the pattern due to the lightning rod). 2. For side mounting of sector antennas on a tower/mast/wall, the mounting spacing to the tower/mast/wall can be reduced to a feasible minimum (i.e. ˜ 0 cm), since the antenna housing acts as an reflector (everything “behind” the antenna has no impact on the pattern). 3.1.1 Side mounting of omni macro antennas on mast/ tower A tower or mast, which usually consists of a good reflecting material (steel, concrete), changes the antenna pattern considerably. Decisive factors are the spacing between the mast and the antenna as well as the mast dimensions. Cylindrical mast

For side mounting of omni antennas on a cylindrical mast the antenna manufacturer can calculate the resulting pattern relatively simply for typical radiation patterns. An exact quantitative degradation calculation can be simulated by the antenna manufacturer. Figure 18 in APPENDIX G shows the degradation of the pattern independent from the frequency range [KAT 1]. It can though be used for RNP purposes, only from a qualitative p.o.v., since e.g. a mast diameter of 0.04 lambda is not feasible. But one can see, that a spacing of 0.25 λ, 0.50 λ, 0.75 λ may be implemented to achieve the desired coverage around the site.

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Some issues arising during antenna installation are not subject of the network design phase. This chapter gives rules for antenna mounting during installation phase.


Lattice tower

For side mounting of omni antennas on a lattice tower the antenna manufacturer can calculate the resulting pattern, but the modeling of each tower element causing reflections (tower legs, bracing, existing ladders and cable traces) is more complex. Typically, larger spacings to the mast always create the risk of unexpected nulls in the pattern. At smaller spacings (0.25 λ / 0.5 λ) the tower leg on which the antenna is mounted, is mainly responsible for the pattern. The principal pattern shapes of „offset“ and „bidirectional characteristic“ still exist, but compared to a cylindrical mast the patterns will have certain irregularities and discontinuities. The exact pattern distortion needs to be simulated by the antenna manufacturer on a case by case study.

3.1.2 Minimum macro antenna height mounting for roof top The considerations in this chapter apply for all cases indicated in Table 30. Antennas are frequently mounted on (flat) roofs. The recommended location for this kind of installation is the roof edge, but for optical reasons the antennas are placed within the roof plane for example on the top/at the wall of an elevator shaft. Depending on the vertical HPBW and the roof shape, the roof plane may create reflections, which cause an uptilt of the resulting final pattern. So, the radiated power towards the roof must be limited, by mounting the antenna with a sufficient height above the roof. The rule is that the first Fresnel zone, which carries the main signal RF energy, shall not be disturbed by any obstacles in the antenna near field (in this case the dominating obstacle is the roof edge; the roof itself represents a strong reflecting plane for RF energy). But the exact determination of the Fresnel zone is hardly possible, due to the variable distance between transmitting and receiving antenna. In the approach of Figure 15 (see [1.1]), the first Fresnel zone is approximized by the antenna vertical HPBW with an additional safety margin (vertical clearance margin) of 20°, which means no obstacle 20° below the 3dB (HPBW) point of the vertical pattern . With ray optics, the allowed distance and height of obstacles in the beam direction of the antenna can be approximized to prevent antenna near field obstruction: H>=D*tan(HPBW/2+dt+20°) Equation 7: Antenna height as function of roof geometry and vertical antenna pattern where dt = downtilt angle omni or sector

omni or sector Downtilt angle

HPBW/2+20°

H

HPBW/2+20°

H

D

D roof side view

roof side view

Figure 15: Mounting distances for a flat roof or a reflective plane It is possible to set a lower vertical safety margin of 10°..15°, as long as the QoS requirements for the site are fulfilled even with a distorted antenna pattern. Example: 8.5° vertical HPBW, 2° dt results in easy to apply rule of thumb: H>=0.5 *D:

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Distance

D [m]:

5

10

>20

Required height

H [m]:

2.5

5

10

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3.1.3 Maximum skew angle for wall mounting of directional macrocell antennas

Max. skew

70° - horiz. HPBW/2

Horiz. HPBW/2 20 °

for a horizontal HPBW of 33°..65°..90° ..(105°) In the sketch, the 20° between the horizontal HPBW/2 and the horizontal line represent a horizontal safety margin.

Wall Trespassing this limit for project needs requires a measurement campaign to verify the fulfillment of QoS requirements for the site even with a distorted antenna pattern.

APPENDIX G shows the qualitative impact of antenna inclination and horizontal HPBW on horizontal antenna patterns for an ideally reflective wall (the antenna radiation characteristics strongly depends on the wall structure and roughness): horizontal antenna patterns are more and more damaged with increasing: ?

antenna inclination angle with reference to the wall perpendicular

?

antenna horizontal HPBW.

Further rules on skewing: ?

Skewing the space diversity antennas mounted on a wall is not recommended.

?

Mounting of directional antennas on building corners as shown in the sketch is not recommended due to: •

shadowing of both Rx-antennas radiation patterns by the Tx-antenna;

•

negative influence on the space diversity performance ⇐ creation of unequal Rx radiation patterns ⇐ mirror imaged reflections

•

increased installation cost and effort

3.1.4 Microcell antenna mounting rules Directional microcell antennas

Omni microcell antennas; crossroad case

For microcell outdoor antennas (in-street or crossroad) the skewing rule mentioned for macrocells (3.1.3) is valid, but maybe harder to fulfill due to the possibly resulting visual impact of the antenna installation. ?

In case of continuous µcell coverage layer, it is recommended to stick to the rule as much as possible.

?

In case of hotspot application cases (majority of microcell applications) violating the rule is not so critical since the service coverage is required only in a delimited area around the site.

The maximum distance R of a cross road omni µcell antenna from the street corner is defined based on experience; recommended angle α is = 20° ; see Figure 16. Omni micro antenna

R

D

Street top view

αmax = 20°

building

Street

Figure 16: Clearance for omni µ cells R = tan(α max) * D = 0.36 * D Equation 8: Clearance for omni µ cells Example: D=50 cm results in R =18 cm For picocell antenna indoor 46/64

(out of documents scope): engineering is mainly determined by visual aspects.

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Maximum azimuth inclination angle (skew) relative to the wall perpendicular for crosspolar antennas and vertical polarized antennas with no space diversity (to prevent excessive antenna pattern distortion):

3.2 Spacing for single band antennas in dual band GSM900/GSM1800 scenario


In a GSM900/GSM1800 scenario, independent whether it is implemented with ?

co-located single band cells

?

or multiband cell

it is possible to use single band antennas for antenna implementation (cf. technical solution 2 in chapter 2.1). In case of Alcatel Evolium A9100, A910 BTS’s, the single band antennas for GSM900 and GSM1800 can be mounted side by side, horizontally or vertically, due to minimum 30 dB, specified and confirmed by decoupling measurements of antenna manufacturers (e.g. in [RFS 1]); 30 dB is sufficient decoupling according to Table 28. Here horizontal side by side mounting means same antenna azimuth.

3.3 Tilt angle implementation The mechanical down-/uptilt to be implemented must be given by the RNE to the installation team in the resolution of 0.5°. A higher resolution e.g. 0.1° cannot be implemented due to the tilt scaling restriction on the antenna.

3.4 Azimuth angle implementation The considerations below are valid for each frequency band. An azimuth angle implementation by the installation team with a compass is highly erroneous due to magnetic perturbation caused by ferrous constructions in the antenna vicinity. Instead the following reliable procedure is proposed to reduce risk of frequent installation errors:

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?

Selection of a prominent obstacle on a good resolution paper map (e.g. building, tower, building, church etc.). If the obstacle is far away it is sufficient to consider its center, otherwise an edge of it (e.g. corner) which can be identified from the site.

?

Map read out of the angular difference ? between the planned azimuth of the antenna and the azimuth of the identified obstacle; the same angular azimuth reference must be used as for RNP (e.g. N over E). If no good resolution paper map is available, the azimuth to the obstacle can be calculated geometrically with the GPS coordinates of the obstacle (must be retrieved) and of the site (already known).

?

Implementation of ? with a tool supplied by the antenna manufacturer (not the compass).

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ABBREVIATIONS

A910 A9100 A955 V5/V6 Anc Anx ANXU Any B7 BBH BTS CDR CSR dBc dBm DL Eb/No EIRP G3 BTS, G4 BTS GSM HO HP TRX horiz. HPBW HSR IM MAPL MHA MP TRX MRC MS OMC-R PCS QoS RF RFS RNE RNP Rx RFH/ SFH TMA TRE TRX Tx UL UMTS-FDD UTRA vert. VSWR XPD

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Evolium A910 micro BTS international standardization body (does the work of former ETSI) Evolium micro BTS Evolium macro BTS RNP tool of Alcatel verion 5 resp. 6 network combining stage duplexer stage Antenna Network for UMTS combiner stage BSS software release baseband hopping Base Transceiver Station call drop rate call success rate decibel carrier decibel miliwatt downlink bit energy to noise ratio equivalent isotropic radiated power (Alcatel internal) release names of Evolium A9100 macro BTS Global System for Mobile Communication handover high power TRX for 900, 1800 horizontal half power beamwidth handover success rate intermodulation (product) Maximum allowed path loss mast head amplifier medium power TRX for 900, 1800 maximum ration combining Mobile Station operation and maintenance center radio Professional Customer Service quality of service radio frequency Antenna manufacturer radio network engineer radio network planning receive radio (synthesized) frequency hopping tower mounted amplifier TRX with GMSK and 8PSK modulation transceiver with GMSK modulation transmit uplink UMTS frequency division duplex UMTS terrestrial radio access vertical voltage standing wave ratio cross polar discrimination

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INDEX 1x1, 19

diversity gain, 56

mechanical downtilt, 53

1x3, 19

dual band, 6, 8

MRC combining, 56

4-Rx diversity, 34

Dual band antennas, 51

narrow beam, 8, 11

A955, 18, 19, 24, 25, 26,

effective antenna height,

omni antenna, 51

29, 30, 34, 48, 53

28 polarization diversity, 28

Additional pathloss, 29

enhanced

diversity

combining, 26, 56

Polarization Rx diversity,

air combining, 6, 8, 9, 25,

57

29, 30, 52, 58

Evolium BTS, 9, 10, 40 remote electrical tilt, 54

antenna near field, 18, 45,

feeder selection rules, 14

64

Sector antennas, 51 fixed electrical tilt, 53

antenna pattern, 21, 29,

SFH, 19, 48

30, 44, 45, 46, 53

frequency bands, 50 Space Rx diversity, 27, 56

antenna selection rules, 6,

Friess, 16, 17, 52, 53

8

TMA, 6, 12, 13, 14, 16, G4 BTS, 16, 17, 48, 56

17, 48, 52, 53

BBH, 19, 48 interference mechanisms, Broadband antennas, 51

transmitter noise, 62

6, 36, 38, 61, 62 triple band antenna, 51

clearance, 10, 18, 45

interference

scenarios,

36, 61

Tx diversity, 31

close proximity scenario, 64

Intermodulation, 36, 63

variable electrical tilt, 8, 53

decoupling requirements,

link budget, 14, 15, 16,

36, 37, 38, 62

17, 26, 29

visual impact, 8, 9, 12, 25, 29, 46, 53, 58

directional antennas, 51

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mast height, 18

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System

FREQUENCY BANDS Total Bandwidth

GSM 850

2x25MHz

Uplink frequency band 450.5-467.5 MHz 824-849 MHz

GSM900

2x25MHz

890-915 MHz

935-960MHz

200 kHz

www.3gpp.org/

EGSM

2x35MHz

880-915 MHz

925-960MHz

200 kHz

www.3gpp.org/

876-915 MHz 17101785MHz 1850-1910 MHz 18501910MHz

921-960 MHz 1805-1880MHz

200 kHz

www.3gpp.org/

not applicable

19201980MHz 19001920MHz (UL+DL) 824-849MHz

2110-2170MHz

5 MHz

www.3gpp.org/

3.84 Mcps

2020-2025MHz (UL+DL)

5 MHz

3.84 Mcps

869-894MHz

1.25 MHz

18501910MHz 824-849MHz

1930-1990MHz

1.25 MHz

1.2288 Mcps 1.2288 Mcps

869-894MHz

30 kHz

18501910MHz 824-845 MHz 1850-1910 MHz 824-849 MHz 871-904 MHz 915-925 MHz 890-915 MHz 940-956 MHz

1930-1990MHz

30 kHz

GSM 450

R-GSM GSM1800

2x75MHz

GSM1900 PCS 1900 (USA) IMT-2000 (UMTS FDD) UMTS TDD

2x60MHz

IS-95 800 (cdmaOne) IS-95 1900

2x25MHz

IS-136 800 US-TDMA IS-136 1900 TDMA D-AMPS 850 D-AMPS 1900

2x25MHz

E-AMPS ETACS NTACS NTM900 PDC900

20MHz + 5MHz

2x60MHz

2x60MHz

Downlink frequency band

Carrier Spacing

869-894MHz

200 kHz

Internet Link

Chiprate

479-496 MHz not applicable not applicable not applicable

1930-1990 MHz 1930-1990MHz

869-890 MHz 1930-1990MHz 869-894 916-949 860-870 935-960 810-826

MHz MHz MHz MHz MHz

Table 31: Frequency Bands

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APPENDIX A

APPENDIX B All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

Omni antenna

ANTENNA TYPES The omni antenna is used in order to achieve large continuous coverage ranges especially in homogeneous, rural, low traffic areas or as an umbrella cell for microcellular networks [1.1]. Main advantages: ?

Continuous coverage is achieved around the site.

?

Antenna installation is more simple than for sector antennas.

?

Better trunking efficiency (e.g. a 6 TRX omni has a higher capacity than a sector site 3x2; provided of course, that there is enough frequency spectrum available to allow a 6TRX omni cell)

Main drawbacks: ?

No mechanical (but electrical) downtilt is possible.

?

Clearance of the antenna is required in all directions: no wall mounting possible, further there are restrictions for side mounting on masts/poles (see ch. 3.1)

?

The omni cell can catch a lot of traffic and get quickly in high load situation if it is not/or can not be equipped with a sufficient number of TRX’s.

?

The omni cell can create a lot of interferences and disturb the frequency reuse; the TRX’s of an omni site require a higher frequency reuse than the same TRX’s in a 3 sector configuration.

Omni antennas are also offered for UMTS as macro and micro antennas. Sector antenna

Sector antennas/directional antennas are typically used: ?

in high traffic areas to increase capacity with sectorized sites;

?

to focus on special areas (road coverage, indoor coverage);

?

to achieve low coverage in regions of low interest (e.g. forest).

Main advantages: ?

Electrical downtilt and mechanical downtilt are possible.

?

Wall mounting is possible.

?

Higher capacity per site can be achieved.

Drawback: more hardware (TRX’s) is required. Typical parameters: gain = 17dBi, horiz. HPBW = 65°…105°, vert. HPBW = 8.5° Dual band antenna

Dual band antennas are characterized by being suitable for two frequency ranges and having two separated input connectors; e.g. GSM900/GSM1800, GSM1800/UMTS, GSM900/UMTS; GSM 850/GSM 1800 Currently dual band antennas are mostly offered as sector antennas.

Triple band antennas

A GSM900/GSM1800/UMTS triple band antenna combines three antennas inside one radome.

Broadband antennas

Broadband antennas serve the specified frequency range with only one antenna inside the radome. E.g.: GSM1800/GSM1900/UMTS or GSM 900/GSM1800/UMTS (frequency range: 890-2170 MHz) Main advantages:

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?

Possibly cheaper price than the respective dual band/triple band antennas;

?

Only a single feeder cable per antenna branch needed;

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No diplexer at antenna side required (but if the broadband antenna is used as a dual band antenna, an additional diplexer at BTS side is necessary per antenna branch).

Main drawback: identical antenna characteristics for all bands, e.g. no different electrical downtilt possible. A broadband antenna shall be selected instead of a dual band antenna only if commercially required (if cheaper). Dual polarized antenna

Polarization is defined as the direction of oscillation of the electrical field vector. Dual polarized antennas are used to integrate two RX antennas in one, reducing the necessary number of antennas on site (gain of space and esthetic). Used with a duplexer, they permit the integration of the TX path on the same antenna. Used with air combining, one TRX can be associated with one polarization direction. Dual polarized antennas are offered only as sector antennas (and not omni).

Microcell antenna Picocell antenna

Repeater antennas

APPENDIX C

Can be offered as single band, dual band, broadband or triple band antennas. They are characterized by esthetical design, suitability for indoor wall/ceiling mounting, low dimension and light weight. Their installation is quick, easy, and unobtrusive. They can be omni, directional, single and dual polarized; they are offered in all frequency ranges. For repeater applications antennas with a high directivity such as Yagi antennas are used for the link between the donor cell BTS and the repeater.

ANTENNA SYSTEMS OPTIONS TMA A tower mounted amplifier (TMA) can be used at a BTS/Node B to improve (i.e. reduce) the effective receiver system noise figure when a long length of feeder cable has to be used, due to high tower/mast heights. The reduction in the receiver system noise figure means an improvement in the uplink power budget. This can be interpreted as compensating the losses between the antenna and the input of the base station: of the feeder+jumper cables, connectors, diplexers, filters ([1.3], [1.6]).

X 900

TMA

TMA

Jumper

Within the TMA, the duplexer separates and recombines the signals on the Rx and Tx paths. It also provides sufficient out-of-band filtering and isolation between the two paths (min 30 dB isolation). Only the RX signal gets amplified by a low-noise amplifier inside the TMA, thus, improving the quality of the UL branch; the TX signal is bypassed to the antenna. For RX or RX/TX antenna diversity operation, the configuration has to be doubled. This means that for each antenna, one TMA unit is required (see figure). If the two units are in the same housing, it is called dual TMA.

Feeder

TMA usage in multiband configurations is possible only if the signals applied to each antenna are single band signals (i.e. the TMA module which is used per antenna is only single band).

BTS

The DC supply of the TMA is done via the RF feeder cable from the Bias-T included in the Node B's antenna unit ANXU. Friess Formula In order to calculate the overall noise Figure of a reption chain, the Friess Formula is used. Equation 9 gives an example (cf. [1.3]) with TMA and no jumper cables:

n tot = n TMA +

n cable − 1 n DX − 1 n BS − 1 + + g TMA g TMA ⋅ g cable gTMA ⋅ g cable ⋅ g DX Equation 9 Friess Formula with TMA

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n element = 10

NFelement 10

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where NFelement is the noise figures in dB and Gelement is the gain in dB of the corresponding element (note that a loss is a negative gain!). The index “element” can be TMA, cable (denotes cables and connectors, here excluding jumper cables), DX (denotes diplexer or filter) or BS (denotes node B). If there are no diplexers or filters in the chain, nDX and gDX are set to 1. In case there is no TMA, the Friess Formala is given in Equation 10:

n tot = n cable +

n DX − 1 n BS − 1 + g cable g cable ⋅ g DX

Equation 10 Friess Formula without TMA

APPENDIX D Scope of downtilt

OVERVIEW ON ANTENNA DOWNTILT With introduction of downtilt, the antenna signal in the main beam direction is focused below the horizon. Downtilt can be achieved mechanically, electrically or with a combination of the two; downtilt can be controlled remotely for certain antenna types. Downtilt improves outdoor and indoor coverage probability close to the site, while with a certain distance away, the coverage probability gets lower; it reduces co-channel interferences by reducing the cell radius or by maintaining cell radius (and reducing the overshoots over the planned cell range); it adjusts cell borders for optimum handovers and removes insular coverage.

Mechanical downtilt

Benefit: it is achieved by the mounting hardware (cost-effective); no antenna swap is necessary. Drawbacks:

Fixed electrical tilt

?

Non-regular coverage reduction is achieved (maximum interference reduction in main direction only). The adjusted downtilt angle is only valid for the main direction of the horizontal radiation pattern. In the tilt axis direction (+/-90° from main beam) there is no downtilt at all. Further, the resulting gain reduction depends on the azimuth direction. This effect is considered in A955 V5/V6.

?

Distortions in horizontal antenna pattern in case of mechanical tilt cause large gain variations i.e. large signal fades ; risk of call drops is increased (see [RFS 2]).

?

The polarization plane is also rotated.

?

Frequent mechanical tilt adjustment (done onsite!) has bad visual impact (site operation outage).

Benefit: the adjusted downtilt angle is constant over the whole azimuth range, so all lobes are equally tilted; this yields an equal reduction of all interferences and a regular reduction of coverage. Drawback: electrical tilt adjustment is not possible (antenna swap necessary associated with visual impact, site operation outage).

Variable electrical tilt

Benefits: ?

Easy cell size tuning according to capacity evolution while minimizing co-channel interferences;

?

For electrical tilt adjustment the antenna remains unchanged => •

No outage on site operation;

•

Cost saving through reduced inventory management.

Drawbacks :

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?

Variable electrical tilt adjustment must be done via control button at the antenna radome (i.e. installer must climb up);

?

Higher price.

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Remote electrical tilt

Benefits (cf. [RFS 2]): For electrical tilt adjustment the antenna remains

? •

No outage on site operation;

•

Cost saving through reduced inventory management.

?

For time being, tilt adjustment is done from the base of the antenna tower via a control unit linked with a cable to a laptop. For the next BSS releases (B8?) it is foreseen to implement an interface to the OMC-R=>tilt tuning without sending crew onsite, i.e reduction of network optimization costs especially for badly accessible sites.

?

Provision of easy adaptation coverage versus capacity and interference control;

?

Control of cells overlapping;

?

No limitation on frequency of tilt tuning;

?

Compatible with future dynamic capacity allocation.

Drawback: possibly elevated price. Upper side lobe suppression

UMTS; Tilt adjustment for optimum traffic distribution

A high first upper side lobe suppression is a mandatory feature for electrically tilted antennas. The drawback of increased antenna length has only a small impact on site geometry and can be tolerated. The first upper side lobe, which is typically in the range of up to max. 20°, is critical for inter-cell interference. Electrical tilt adjusts antenna footprint: it minimizes inter-cell interference while maintaining cell coverage. Both coverage and inter-cell interference are traffic dependent =>optimum tilt value to control inter-cell interference is traffic dependent. In inhomogeneous traffic scenarios: ?

Reduce footprint of highly loaded cells by increasing electrical tilt.

?

Enlarge footprint of lower loaded cells by decreasing electrical tilt.

Scope: ?

Avoid overload in single cells

?

Even traffic distribution between cells

Table 32 below presents the application area of UMTS adjustable tilt: Remote electrical tilt Variable electrical tilt Inhomogeneous traffic Inhomogeneous traffic distribution distribution High time dependency of Low time dependency of traffic traffic Table 32: Application area of UMTS adjustable tilt

APPENDIX E

Fixed electrical tilt Homogenous traffic distribution Very low time dependency of traffic

OVERVIEW ON ANTENNA DIVERSITY Purpose

The purpose of using diversity is to reduce short-term fading effects, such that an acceptable level of performance (receiver sensitivity) can be achieved, without having to increase the transmitted power or the bandwidth.

Principle

The principle relies on the combination of two or more signals, containing the same information, which are at least partially decorrelated. If two signals of the same level are completely decorrelated, the probability that both signals experience the same depth of fade is only the square compared to the probability for one signal. Therefore the signal reliability is increased.

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The diversity types which are subject of this document are:

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Category GSM yes yes yes n.a. no no

Rx diversity

space div. polarization div. space div. + polarization div. 4-Rx diversity space div. + polarization div. Tx diversity space div. polarization div. Figure 17: Overview on diversity types

Applicable in UMTS yes yes n.a. yes yes yes

Only two Rx diversity systems are subject of this document: ?

For space diversity, the decorrelation is achieved by receiving the signals with two spatial separated (horizontally or vertically) antennas.

?

For polarization diversity, decorrelation is achieved by using antennas with different polarization planes (horizontal/vertical or cross, i.e. +/-45°).

To achieve a maximum Rx diversity gain it is required to have [2.1]: ?

high signal decorrelation between receiver paths

?

low signal level difference between receiver paths (due to the maximum ratio or enhanced diversity combining methods in the Alcatel BTS which weighten the signals in proportion to their signal/noise ratio, see APPENDIX E ).

With space diversity better signal decorrelation can be achieved. MRC combining

The G3 receivers in the Alcatel BTS use the maximum ratio combining (MRC) method. The MRC method does not reduce the interference level received from other mobiles using the same frequency(ies) (co-channel interference) or from adjacent frequencies (adjacent interference). It only improves the received signal by steering a beam into the direction of the mobile; it estimates the phase difference between the two antennas, corrects this phase difference, weightens the signals in proportion to their signal to noise ratio before the co-phased signals are added; there is coherent addition of the signals and incoherent addition of the noises; this increases the signal to noise ratio. MRC combining offers:

Enhanced diversity combining

•

Very good performance under noise limited conditions; for diversity gain see Table 23: 3 – 6 dB improvement compared to no antenna diversity.

•

Less improvement under interference limited condition;, up to 3 dB diversity gain compared to no diversity.

The G4 receivers in the Alcatel BTS (G3 BTS or G4 BTS) use the enhanced diversity combining method. This feature is available from B6.2 BSS software release onwards. The enhanced diversity combining uses several algorithms: ?

There is an beam forming algorithm to improve the received signal by steering a beam into the direction of the mobile (like in MRC method).

?

But moreover, there is an algorithm to reduce interference: it cancels interferers by steering a null into their directions (it estimates the phase difference between the two antennas for the interfering signals and then, it rejects these interfering signals by adding the signals with an inversed phase).

Enhanced diversity combining gives its best efficiency when the useful signal and the interfering signals come from different directions. Space Rx diversity

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?

Principle: during a deep fade at one Rx antenna location, the fade will not be as severe at the other Rx antenna location, if the two Rx antennas are sufficiently separated. For space diversity, reflections are not so important.

?

Advantages:

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Diversity type


•

UL improvement (optimum diversity gain for wide area);

•

Space diversity works better than polarization diversity in rural environment (characterized by wave propagation with few reflections).

?

Drawback: possibly large space requirement for sufficient Rx antenna separation=> expensive tower/mast construction. (An alternative can be to mount the diversity Rx antennas on 2 separate poles constructed in the required distance; equal feeder length required).

?

Principle: polarization decorrelation of the different signal rays which encounter different multipath reflections while traveling between the MS to the BTS. So the reflections are mainly important for polarization diversity, since they change the wave polarization.

?

Advantages:

Polarization Rx diversity

•

UL improvement (diversity gain);

•

2 Rx antennas with different polarizations mounted under the same radome;

•

No need for large site structures as in case of space diversity.

Drawback: effective only in high multipath environments. UMTS-FDD Tx diversity

The aim of transmit diversity is to alleviate fast fading and therefore to increase the capacity of the downlink transmission. The transmit antenna diversity technique consists in using at the transmitter several antennas, broadcasting complementary signals. To implement the TX diversity feature, two power amplifiers per sector are needed. Adding a power amplifier will double the available output power (3dB gain on output power); this gain of 3dB is not a diversity gain in the original sense of the word, but merely linked to the second power amplifier. Several transmit diversity techniques have been standardized in the FDD mode of UMTS for two transmit antennas: ?

?

open loop transmit diversity •

TSTD, Time Switched Transmit Diversity (for the DL synchronization channel)

•

STTD, Space Time Transmit Diversity (for traffic channels)

closed loop transmit diversity mode 1 and mode 2.

Antenna transmit diversity is provided optionally for UMTS-FDD Node B, but it is mandatory for the MS. It can be switched-on on a per channel basis. The MS (with omni, vertical polarized antenna) uses the maximum ratio combining method to combine the 2 DL signals. Support by HW and SW: Open and closed loop are supported by Evolium Node B; but in R1 only 'closed loop Tx diversity mode 1' is implemented. In R2 neither open loop nor closed loop TX diversity are implemented. Important characteristics for cross polar antennas

The isolation between ports is the attenuation between the branches in near field. In contrary the cross-polar discrimination is the attenuation between the two branches in far field. Antenna inter-port isolation: Denotes the ratio in dB of the power level applied to one port of a dual polarized antenna to the power level received in the other input port of the same antenna. Typical value is minimum 30 dB. Cross polar discrimination (XPD): The difference in dB between the co-polarized main beam signal and the cross-polarized signal measured within an angular zone in azimuth of twice the maximum half power beam width of the frequency band. E.g. for a 65° hor. HPBW antenna , XPD is measured both in the main axis and at 60° opening angle. Typical value is 30…35 dB minimum. The better the cross polarized discrimination is, ?

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the better the diversity gain of the antenna;

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APPENDIX F

the lower the level of disturbing signal (coming from the opposite slant) is, in order to insure a safer reception.

PRINCIPLE OF AIR COMBINING The idea of air combining is to combine transmitted signals in the air and not with an BTS internal combiner, in order to avoid combining losses. Each TX-signal will be transmitted via a separate antenna. With air combining combiner losses can be saved (depending on the number of saved combiner stages, i.e. on the number of TRX’s), resulting in a lower path loss in the DL. This results in an improved coverage range for macrocells or in an improved indoor coverage for microcells. Air combining can be realized with: ?

two sector or omni antennas (vertical polarized)

?

one cross polar antenna transmitting different carriers on +-45°.

Thus cross polar antennas allow air combining configurations with a single antenna. Remark: Air combining with horiz./vert. polarized antennas is not recommended, since there are losses of typ. 3 dB on the horizontal polarization direction, assuming a vertical polarized MS antenna (see also ch. 2.7.3).

APPENDIX G

ANTENNA PATTERN DISTORTION FOR DIFFERENT MOUNTING SCENARIOS Refer to [KAT 1]. Regarding Figure 18: Spacing 0.5 λ An increase of the spacing to 0.5 λ creates a bi-directional pattern perpendicular to the line antenna – mast, which becomes more characteristic with bigger mast diameters. This pattern shape provides 2-3 dB more gain and could be applied for the coverage of highways and railway lines. Spacing 0.75 λ At a spacing of 0.75 λ a further beam grows in the direction of the antenna; a tridirectional pattern is formed. Spacing 20 λ The number of beams becomes greater and the depths of the corresponding minima become smaller as the spacing is increased; the pattern changes back into an omni characteristic. However the influence of the mast can still be recognized up to spacings of 20-25 λ. Such a spacing of 20 lambda is not feasible due to heavy visual impact but shows the behaviour from a qualitative p.o.v. Regarding Figure 19, Figure 20: The antenna radiation characteristics strongly depends on the wall structure and roughness. Figure 19, Figure 20 are given for an ideally reflective wall (such as concrete walls or aluminum covered facades.

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Figure 18: Typical radiation pattern distortions of mast side mounted omni antenna

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Figure 19: Typical horizontal radiation pattern distortions of wall mounted GSM900 directional antennas;22 ° inclination

Figure 20: Typical horizontal radiation pattern distortions of wall mounted GSM900 directional antennas;45° inclination 60/64

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APPENDIX H

INTRA-/INTER-SYSTEM COMPATIBILITY

Intra-/Inter-system compatibility

Intra-system compatibility guarantees no disturbances due to interference mechanisms within the same communication system ?

1 system, 1 operator

?

1 system, 2 operators (e.g. UMTS-UMTS co-siting on multi operator site)

Inter-system compatibility guarantees no disturbances due to interference mechanisms within the different communication systems

Interference scenarios

?

2 system, 1 operator (e.g. GSM1800-UMTS co-siting operated by same operator)

?

2 system, 2 operator (e.g. GSM1800-UMTS co-siting on multi operator site)

The following interference scenarios are generally valid for any type of cellular systems. Two different cellular systems shall cover the same area. The co-existence of two systems or even site sharing means, that there are 4 possibilities that interference arise. Serving Base Transceiver Station

Interfering Base Transceiver Station

I

S

S

I

S I

Figure 21: Two cellular systems covering the same area The different combinations of interference disturbing the serving BTS and the MS, which is dedicated to the serving BTS, is shown in the following picture. Some abbreviations are used: S=Serving; I=Interfering; green=carrier; red=interferer signal Serving Base Transceiver Station


I-BTS DL à S-BTS UL

I

S

S

I

S I

Serving Base Transceiver Station


I-BTS DL à S-MS DL

I

S

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I

S


I-MS UL à S-BTS UL

S

I

S I



I-MS UL à S-MS-DL

I

S

S

I

S I

Figure 22: Interference scenarios The four combinations of Figure 22 are: Transmitter Link creating /Interference source interference BTSàBTS BTSàMS MSàBTS MSàMS

I-BTS I-BTS I-MS I-MS

DL DL UL UL

Receiver

Link which is interfered

S-BTS S-MS S-BTS S-MS

UL DL UL DL

Table 33: Interference scenarios Planning a radio network mainly means planning site locations for transceiver stations. Therefore BTS à BTS interference problems can be reduced or avoided. The BTSàMS interference comes from a interfering BTS. Normally, the influence on planning this configuration is low, if another operator handles this network. The MS à BTS situation is only taken into consideration by planning the BTS, with all its attributes like antenna height, antenna orientation, and so on. The location of a mobile user can have a big variety. In the MSàMS scenario, it is not avoidable, that two mobile users of different systems get close to each other. So the focus is on combating the BTS à BTS interference scenario. Co-location of base stations may cause interference resulting in performance degradation. In order to minimize this performance degradation to an acceptable defined level, decoupling requirements between the systems have to be met. Interference mechanisms

The most important interference mechanisms are: Transmitter noise/ spurious emissions The transmitter noise floor or transmitter spurious of system "A" within the receive band of system "B" causes interference of system "B´s" receiver and vice versa. This could be avoided by increasing the stop band attenuation of system "A´s" antenna network in the transmit path for the receive band of system "B", or by increasing decoupling between the two systems, either the air decoupling or the decoupling provided by diplexer. Receiver blocking

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Transmit signals of system "A" are blocking the receiver of system "B" and vice versa. This could be avoided by increasing the stop band attenuation of system "B´s" antenna network in the receive path for transmit frequencies of system "A", or by increasing the decoupling between the two systems (air or diplexer decoupling). All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.

Intermodulation (IM) products Significant intermodulation products are generated in nonlinear devices (especially mixers and amplifiers but also connectors), if two or more strong signals are applied. Intermodulation problems due to co-location might rise, if transmit carriers from the co-located system "A" generate intermodulation products falling into a used receive channel of system "B" or vice versa. Also a combination of transmit frequencies of both systems might fall into a used receive channel of either system "B" or system "A." ?

IM can occur within one system, without co-location of any other system (1 system, 1 operator); this is an intra band IM; condition: both frequency signals are applied on the same duplexer

?

IM can occur between 2 co-located systems; condition: antenna and/or feeder sharing (there are no IM between 2 co-located systems if this condition is not given) •

Intra band IM: can happen on multi operator sites (e.g. UMTS-UMTS colocation: 1 system, 2 operators)

•

Inter band IM: can happen on multi operator sites (e.g. GSM1800-UMTS colocation: 2 systems, 2 operators ) or on single operator sites (e.g. GSM1800-UMTS co-location- 2 systems, 1 operator)

General formula for IM products: fIM = m • f1 + n • f2

with m, n = 0, +1, +2, +3, ...

where the order of the IM product=|m|+|n|; only positive fIM make sense. Only low order IM products are critical; the higher the IM order, the less their power and the less critical the IM products are. The reference point for IM products inside a used Rx channel is the BTS antenna connector. As long as the signal level of the interfering critical IM product is well below the systems noise floor, almost no receiver degradation, and thus no problem due to IM will occur. The total intermodulation level compared to a power-rating of 1 mW is expressed in dBm: IM = 10 log PIMP3 [dBm] . On the other hand, dBc is defined as the ratio of the third order intermodulation product to the incident Tx carrier signal power: IM = 10 log(PIMP3/P Tx ) [dBc] .

APPENDIX I

MISCELLANEOUS

Antenna mounting location For outdoor macrocell antennas it is possible to have the following cases: ?

tower/mast/pole: top mounting or side mounting;

?

roof: top mounting;

?

wall: side mounting.

Microcell outdoor antennas used for in-street coverage are mounted on the wall/pole but below rooftop and the ones used for crossroad coverage are mounted on a pole. Antenna near and far field

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The antenna radiation behaviour is splitted in a near and a far field characteristic. Typically the antenna radiation characteristics given in antenna catalogues are valid for the far field. The near field antenna radiation characteristic depends on tower /mast /wall construction elements and the antenna dimensions; it is not depending on the far field radiation characteristics. Edition 01

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The range of the antenna near field is dependent on the maximum size of the antenna aperture D (i.e. antenna length) and the wavelength λ. It can be estimated with the following deterministic formula: Rmin=2D²/λ Typical values for macro antennas are: GSM900 (D = 2.5 m; λ= 33 cm; Rmin = 38 m) GSM 900 (D = 2.0 m; λ= 33 cm; Rmin = 24 m GSM1800 (D = 1.3 m; λ= 16 cm; Rmin = 21 m) UMTS (D = 1.3 m; λ= 14,6 cm; Rm i n = 23 m) Close proximity scenario (µ cell)

An indoor mobile is connected to micro BTS 1, while another mobile being connected to micro BTS 2 might turn around the corner and have sudden direct line of sight condition to micro BTS 1. In such a scenario there is a high risk of µBTS receiver inband-blocking. In order to achieve a sufficient minimum coupling loss between mobile antenna and BTS receiving antenna the mounting height has to be accordingly high, taking into account the following two basic items: ?

In order to increase the minimum coupling loss between MS and BTS, the antenna should be positioned as high as possible.

?

With increasing mounting height the interferer potential will be increased, especially since microcells often are planned with a reduced Reuse Cluster Size.

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There should not be any obstacles within the near field since the antenna diagram is then severely disturbed.

Antenna System Planning

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