2g Radio Network Optimization Training ( Practical Workshop)

2G Radio Network Optimization Technology Training Network Planning & Optimization Veeresh N

1

© Nokia Siemens Networks

NPO 2G Radio Network Optimization Technology Workshop--veeresh

Course Outline •

DAY 1---CALL FLOW ( MTC& MOC)& Network Optimization Principles( Parameters ,Hoc, Poc, Timers)

•

DAY2- Network Performance Optimization(Counters, KPIs, ND Reports)

•

DAY 3-- AMR TRAINING & FEATURES PRESENTATION(Robust AMR , AMR PPC, SAL)

Soc Classification level 2 © Nokia Siemens Networks

Contents Channels –Basics Mobile Originated Call—MOC Mobile Terminating Call—MTC Handover control ---HOC Power Control –POC  Parameters Timers


Presentation / Author / Date

Logical Channels on Air interface LOGICAL CHANNELS

DEDICATED CHANNELS

COMMON CHANNELS

COMMON CONTROL CHANNELS

BROADCAST CHANNELS

FCCH

SCH

BCCH

PCH

DEDICATED CONTROL CHANNELS

SDCCH

RACH

AGCH

SACCH

TRAFFIC CHANNELS

FACCH

TCH/F

TCH/H 4

4


TCH/EFR

GSM Channels GSM Channels Traffic Channels (TCHs)

Control Channels

Broadcast Channels (BCHs) Full rate

Half rate

Common Control Channels (CCCHs)

Dedicated Control Channels (DCCHs) (down uplink)

Downlink

Downlink

Uplink Fast

Slow

TCH /F TCH /HFCCH SCH BCCHPCH AGCH CBCH RACHSDCCH FACCH SACCH Traffic Multiframing Soc Classification level 5 © Nokia Siemens Networks

Signaling Multiframing

Traffic Multiframin 5

The Logical Channels on Radio Interface TS

0123456 7

BTS

MS FCCH

TCH

Frequency correction Synchronization

Traffic (speech-data) SCH

FACCH

Associated Signaling

BCCH Broadcast control RACH Access request Subscriber paging Answer to Access request

PCH

SACCH SDCCH

Radio Measurement + SMS Dedicated Signaling

CBCH Broadcast info

AGCH FCCH CBCH

Broadcast info Dedicated Signaling

SDCCH SACCH

Sys InFo 5, 6 + SMS

SCH

M.S. Pre-synchronization

BCCH RACH Access request PCH

Traffic (speech data) TCH Associated Signaling FACCH Soc Classification level 6 © Nokia Siemens Networks

Subscriber paging AGCH

Answer to Access request

6

Logical Channel Description (1/2) SACCH MESSAGES TCH MESSAGES Measures:

- power level of the communication

• Speech

- quality level of the communication

• Data

- level on the beacon frequency of the

• Handover Access message (uplink)

neighboring cells • Timing Advance

• Power Control • SMS

FACCH MESSAGES • Connection establishment from SDCCH

to TCH SDCCH MESSAGES • Request for a SDCCH assignment • Request for the end of channel

assignment • Order of commutation from SDCCH to

TCH • SMS Soc Classification level 7 © Nokia Siemens Networks

• End validation of a SDCCH-TCH

commutation • Characteristics of the future used BS

after handover • Connection establishment to BS after

handover • Validation of an handover

7

Logical Channel Description (2/2) FCCH MESSAGES

AGCH MESSAGES

• no message is sent (all bits 0)

• For dedicated channel assignment:

SCH MESSAGES • Frame Number

- frequency number - slot number - frequency hopping description - Timing Advance (1st estimation) - MS identification

• Base Station Identity Code (BSIC)

CBCH MESSAGES BCCH MESSAGES

• Specific information

(weather, road information • System Information type 1, 2, 2bis,

2ter, 3, 4, 7, 8 (idle mode)

RACH MESSAGES • Service request:

PCH MESSAGES • messages containing a mobile

identity for a call, a short message or an authentication Soc Classification level 8 © Nokia Siemens Networks

- emergency call - answer to an incoming call - outgoing call - short message - call re-establishment - inscription

8

Mobile Originated Call – – – – – – –

Request for Service Authentication Ciphering Equipment Validation Call Setup Handovers Call Release


9

Call establishment from a mobile--MOC Mobile looks for BCCH after switching on RACH send channel request AGCH receive SDCCH

SDCCH send call establishment request SDCCH do the authentication and TMSI allocation SDCCH send the setup message and desired number

SDCCH require traffic channel assignment FACCH switch to traffic channel and send ack (steal bits) FACCH receive alert signal ringing sound FACCH receive connect message FACCH acknowledge connect message and use TCH Soc Classification level 10 © Nokia Siemens Networks

TCH conversation continues

Call establishment from a mobile--MOC csf_1a csf_2e

csf_2e


CONTINUE

csf_2e

blck_8d dcr_3i dcr_3j dcr_4e blck_29

dcr_8c dcr_8e

dcr_5a Soc Classification level 12 © Nokia Siemens Networks

dcr_5a dcr_8c dcr_8e

dcr_3i dcr_3j dcr_4e


Call establishment to a mobile--MTC Mobile looks for BCCH after switching on Mobile receives paging message on PCH Generate Channel Request on RACH Receive signaling channel SDCCH on AGCH Answer paging message on SDCCH Receive authentication request on SDCCH

Authenticate on SDCCH Receive setup message on SDCCH Receive traffic channel assignment on SDCCH

FACCH switch to traffic channel and send ack (steal bits) Receive alert signal and generate ringing on FACCH Receive connect message on FACCH Soc Classification level 14 © Nokia Siemens Networks

FACCH acknowledge connect message and switch to TCH

Mobile Terminated Call MS Paging Request Channel Req

Imm Assgn Paging Response

Paging Command

Channel Actvn Chan Actvn Ack Imm Assgn Establish ind

Alert Connect Connect Ack Speech

Company Confidential

Paging

Channel Reqd

CM Service Accept Security Procedures Set Up Call Proceeding TCH Assignment


MSC

BSC

BTS

CL3 Informant

Paging   

Paging is process by which Mobile receives incoming calls Mobile has to monitor the paging channel to receive paging messages Mobile will not monitor all paging channels, it will monitor the channel specific to its CCCH_Group and Paging Group

CCCH_ GROUP      

BCCH defines the number of PCHN ( timeslots ) supporting CCCH CCCH can be allocated only to TN 0,2,4,6 CCCH will have the same structure on all allocated timeslots ( 9 blocks ) Each PCHN supporting CCCH is alloted a CCCH_Group No ( range : 0 .. 3 ) Each CCCH_Group carries its own group of Mobiles. Mobiles will listen to paging messages and send RACH's only in their specific group

0 1 2 3 4 5 7 6

B D C T C T C T 9 b l o c k s 9 b l o c k s 9 b l o c k s 9 b l o c k s



Paging Group 



Within the CCCH_Group , Mobile listen to paging in specific paging (CCCH) blocks only The block specific to a mobile is its Paging Group

T N

F S B C F S C C F S C C F S C C F S C C I 0 D 1

I S B C I I C C I I C C I I C C I I C C I 2 T 3



C C C H _ G R O U P



P a g i n g G r o u p

Paging How to derive CCCH_Group and Paging Group for a mobile ? Let us understand some parameters required to achieve this .

1. BS_CC_CHANS : Total No of PCHN supporting CCCH ( Sys Info Type 3 ) Range : 1 - 4 2. BS_AG_BLKS_RES : Blocks reserved for AGCH 3. BS_PA_MFRMS : Multiframe Repetition rate

4. IMSI : 15 digit Mobile Identity

We will now understand 2 & 3



Paging Available Paging Blocks on 1 CCCH_Group Available Paging Blocks = CCCH Blocks -- bs_ag_blks_res Maximum AGCH Reservation for Non-Combined = 7 Available Paging Blocks = 2 Maximum AGCH Reservation for Combined = 2 Available Paging Blocks = 1 Mimimum AGCH Reservartion for Non-Combined = 0 Available Paging Blocks = 9 Minimum AGCH Reservation for Combined =0 Available Paging Blocks = 3 No of Paging Blocks will have a range of 1 - 9 Soc Classification level 19 © Nokia Siemens Networks


Paging BS_PA_MFRMS -- No of Multiframes after which Same Paging Group is repeated -- This Parameter is broadcasted on BCCH -- Ranges between 0 -- 9 Multiframes

F S B A F S A A F S A A F S A A F S I P 0 P 1

M F 2


M F 3


Mobile belonging to Paging Group P0 will remain idle during P1 ,P2,P3 Mobile utilizes power only during PO. This is known as DRX Soc Classification level 20 © Nokia Siemens Networks


Paging Total No of Paging Groups on 1 CCCH_Group ( N )

No of Paging Groups = Paging Blocks x Repitition of Paging BLock N = [ CCCH - bs_ag_blks_res ] x bs_pa_mfrms

Range of Paging Groups on 1 CCCH_Group Minimum Available Paging Groups = Min Pag blocks x Min bs_pa_mfrms = 1 x 1 = 1 Maximum Available Paging Groups = Max Pag blocks x Max bs_pa_mfrms = 9 x 9 = 81



Paging How does a Mobile knows it CCCH_Group Paging Group No ?

CCCH_Group = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] div N

Pag Grp No = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] mod N

N = Total Paging Groups = No of Paging Blocks x bs_pa_mfrms



HOW TO WORK OUT WHICH PAGING GROUP AN MS IS ASSIGNED TO • •

The paging group is determined by the following: PAGING GROUP = {(IMSI mod 1000) mod [BS_CC_CHANS*N]} mod N

•

Where N = No of Paging Groups = No of PCH x BS_PA_MFRMS IMSI = International Mobile Subscriber Identity Mod = MODULUS (see additional notes on modulus at the end) BS_CC_CHANS = CCCH (COMBINED (3) or NONCOMBINED (9)) Example: Assuming that the relevant parameters for the calculation are as follows: IMSI= 460003811319045 N = Number of Paging Groups (For this we will assume there are 28 Paging Groups) Mod = Scientific calculation. Full notes at end explaining mod. BS_CC_CHANS = 9 (As we will assume for this that NON-COMBINED Signaling is in use)


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© 2005 Nokia

V1-Filename.ppt / 2005-02-15/ sr

CALCULATION So the calculation {(IMSI mod 1000) mod [BS_CC_CHANS*N]} mod N based on the information in the previous slide would be as follows: {(460003811319045 mod 1000) mod [ 9 * 28 ]} mod 28 STEP1. (IMSI mod 1000) = (460003811319045 mod 1000) 460003811319045 / 1000 = 460003811319.045 mod then requires removing the whole number and multiplying the remainder by the original mod number. This would give 0.045 *1000 = (45) STEP2. From previous slide, (BS_CC_CHANS*N) BS_CC_CHANS = 9 Number of Paging Groups (N) = 28 (9 * 28) = (252) STEP3. {(IMSI mod 100)mod[BS_CC_CHANS*N]} = {(45) mod [252] } 45 / 252 =0.1785 mod requires removing the whole number however as there is no whole number in this case then the remainder is multiplied by 252. This would give 0.1785 * 252 = 44.982 (Round up to 45) STEP4. Result obtained in Step 3, mod 28, therefore: (45) mod 28 45 / 28 = 1.6071 mod requires removing the whole number and multiplying the remainder by the original mod number. This would give 0.6071 * 28 = 17 Therefore we conclude that IMSI 460003811319045 belongs to Paging Group 17. For More information on Paging Groups see GSM Specification 05.02.


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© 2005 Nokia


MODULUS EXPLAINED •

What is MODULUS?

• If you divide 14 by 4 you get an answer of 3 plus a remainder of 2. • When using MODULUS the remainder is the important bit, the ‘whole’ number is discarded. • Example 14/4 = 3 remainder 2, discard the whole number (3) leaving the answer 2, the maths for this would be written in the form: [14] mod 2.


25

© 2005 Nokia


MTC _CALL FLOW •

PSR = (first paging response+ repeated paging response)*100/first paging request The following formula indicates the success rate of paging (call & SMS) 100* sum(succ_page)/sum(fail_page+succ_page) Paging (MSC to BSC ;BSSMAP) • This message is sent by MSC when it has found out the called MS is somewhere under him (= MSC recognises this is a GSM_END -call). This message contains mainly four kind of information: message type, IMSI of the called subscriber, TMSI of the called subscriber and Cell Identifier list. If TMSI -numbers are defined for use these have the priority one, for security reasons and if the network does not use TMSIs then IMSI -number is included only. The paging is sent as an UDT (Unit Data) message to the BSC.

•

•

Paging Command (BSC to BTS ;BTSM) The BSC always calculates so-called paging group. The idea of this calculation is to find out in which radio time slots the BTS can send the Paging Requests out towards the MS. Reason: in the network, there is a possibility to have at least three different kind of BCCH-TRX -radio time slot configurations and thus logical channel PCH can have at least three different kinds of location. If the BSC receives both TMSI and IMSI from the MSC, then it uses always TMSI number when sending paging further on. Paging Request (BTS to MS;PCH) The BTS sends paging on a PCH channel.



Major Issues that affect Paging Performance SMSC

MSC A - Interface

BSC LAPD (Abis) Interface

LA BTS 1

LA BTS 2

BTS

• •

SMSC Capacity Utilization

• • • •

A Interface( SS7) Signaling Load

• •

BCSU Processor Overload – Lower/Upper Limit Issues

• •

LAPD Load – Against the Signaling Link Used ( 16/32/64Kbps)

• •

Paging Deletion in Cells

• • • •

Cell Reselection Strategy ( HYS - Specially in LA borders)

Page Time Out

Page Time Out VLR Subscriber Capacity BHCA ( SMS & Voice)

Example of smart Network -Philippines

BSC Hardware Utilization

Paging Load ( High Page Volume) Above Capacity Limits

RACH Collisions – Overload

BTS

Air - Interface

Overshooting of Cells beyond the desired boundary Distant & Un-necessary neighbor relations Poor Coverage & Quality

MS MS

Other than Capacity Issues, PAGE TIME OUT is the main reason that is Soc Classification level to be analyzed 27 © Nokia Siemens Networks

Paging Scenario in SMART

Conclusion

• TMSI is used for both INITIAL PAGING & PAGE REPETITION • Re-page Interval ( INT3.5 Sec ) • Re-Paging Attempts is 1 ( PAGE IS REPEATED ONCE) • TMSI Re-Allocation is not done during MT Call & MT SMS


Network Element Capacity & Interface Analysis - SMSC SMS Assessment – No Page Response

Clear Code 12 (NO PAGE RESPONSE) - Reasons • Paging time out • Subscriber is not reachable • No response to paging message

Possible reasons • Mobile Station Reason • MS does not give the response to the paging message • Network Availability Issues • Out of Coverage Area • During Location Update Process / LU Update Failure

Detailed analysis of Trace is in next slidex Soc Classification level 29 © Nokia Siemens Networks

Network Element Capacity & Interface Analysis - SMSC B-Subscriber is in Same BSC ( In this case BSC48)

Time Out after

MT SMS to Same Customer But Took 2 RETRY

•DX Cause 0x12 indicates NO PAGE RESPONSE ( Or Page Failure MS in same location – User A sends SMS to User B

• NO PAGE RESPONSE to

1st Attempt Including, REPAGE ( Time

Out after 7 Sec) • PAGE SUCCESFUL in 2nd RETRY , but 5.66 Sec Page Response time Indicates need to increase INT ( Re-page Interval) as MS took long time to RESPOND SMS Assessment – No Page Response


Network Element Capacity & Interface Analysis - SMSC SMS Assessment – No Page Response

B-Subscriber switches between 2 BSC Report Time Length 19.07.2009 9:16:20 PM 59 19.07.2009 9:19:06 PM 59

Orig Calling No Msisdn Number 639103106764 639071071672 639103106764 639071071672

Bsc Id 48 145

Lac 12145

Cell 21704

Paging Time Dx Cause 402

0x12 0x0

Finding from Trace file : • B Subscriber switches between 2 LACs. • When the subscriber was paged 1st time, the MS may be under location update process & NO PAGE RESPONSE • Again after 2 min 46 Sec , the customer was again Paged with new LAC / Cell ID • Page was Successful, again the response time was 4.02 Sec.

Main Observations • Location update and/or Cell Reselection process took more time. Observed high setting of Cell Reselect Hyst • However its evident that the Page Response time is high as 4.02 Sec, After 1st SMS delivery attempt failed. • In SMART the Page Response Timer ( INT- Re Page Interval) is set at 3.5 Sec.

1. Need to increase Re- Page interval from 3.5 Sec  4.5 Sec 2. Review Cell Reselect Hysteresis (HYS) in Cells at LAC border. Example in later slides ( Slide 22) Soc Classification level 31 © Nokia Siemens Networks

Paging Success Rate – Snapshot 200,000

100

180,000

90

160,000

80

140,000

70

120,000

60

100,000

50

80,000

40

60,000

30

40,000

20

20,000

10

0

Paging Successful rate

Paging Attempt

Paging Attempt vs. Paging Successful rate (per LAC) MSCG11

0 10145 11145 12145 13145 14145 15145 16145 17145 10048 11048 12048 14048 BSC11145

BSC48 LAC/ BSC

Sum of PAGINGATTEMPTPERLA

Sum of PAGINGSUCCRATE

Source: VLR measurement report, paging per LAC (353/161H), 30 Jun 09 21:00

Average Paging Success Rate is less than 85% in LACs of MSCG11 Page Volume is quite high across all LACs when compared to “No of Cells in LAC” ( L Snapshot of this in the following slide. Soc Classification level 32 © Nokia Siemens Networks

LAPD ANALYSIS—Paging



Network Element Capacity & Interface Analysis - MSC •

A Interface Signaling Link Load ( MSC  BSC)

XVSFDVG

1 0.9 0.8

Erlangs

0.7 0.6 B1148 BS145

0.5 0.4 0.3 0.2 0.1

2009-07-22

2009-07-20

2009-07-19

2009-07-18

2009-07-17

2009-07-16

2009-07-15

2009-07-14

2009-07-13

2009-07-12

2009-07-11

2009-07-10

2009-07-08

2009-07-07

2009-07-06

2009-07-05

2009-07-04

2009-07-03

2009-07-02

2009-07-01

2009-06-30

2009-06-29

2009-06-28

2009-06-27

0

Date

• All of Signaling links towards BSCs (BSC1148 and BSC145) are overload during busy hour. • The average are 0.34 Erlang since before and after new promotion. • NSN recommended Value is 0.2 Erlang. Recommended to change few VLR/PLMN Parameters to reduce the Signaling Load. Ref: Next Slide


Network Element Capacity & Interface Analysis – BTS & Air Interface • Cell Overshooting, beyond the expected • Increased number of Adjacency in other LAC ( As a result of more LACs)

Example Case of Cell SH08FTPNR3 is shown in next slide Cell SH08FTPNR3 which is in LAC border , Overshoots to 3.8Km reaching the 2nd neigh This Cell has high RACH deletions and considerable Page Deletions Soc Classification level 35 © Nokia Siemens Networks

ND Report--Paging Deletion--186



Cell having AG Deletion—ND 202



BCSU LOAD—ND 184



Summary of Recommendations – for Improving Paging Performance NSN Recommendation to maintain good Paging Success Rate

Once Paging Success Rate is improved after implementing the recommendations in previous slide, following activities has to be done or monitored to maintain Good Paging Success Rate

• • • • • •

•

Maintain the A Interface (SS7) signaling load below 0.2 Erls ( Currently its above 0.34 Erls) Traffic Migration from MSCG11 to other MSC to reduce the Traffic Load. Remove INACTIVE BSCs ( definition) from MSCs . ( MSCG11 has only 2 BSCs where defined are 7) Monitor & maintain BCSU Load in safe limits – Less than 60% Average Load Reduce the number LACs ( Combine LAC if Page load is less) Paging Load ( LAPD limits). Minimum 32Kbps LAPD signaling is to be used. If LAPD Overload Alarm(2133) is present in few Cells, increase to 64Kbps Implement the Layering Analysis & Recommendation from NSN.


Paging Optimisation • Paging is a procedure in which the PLMN attempts to reach a mobile subscriber within the location area in which the subscriber is currently registered. In a mobile-terminated call, the MSC/VLR sends a paging order to the BSCs /RNCs controlling the last location area of the mobile station. To be able to do this, the MSC/MSS has to know which BTSs belong to which location areas and by which BSCs/RNCs they are controlled. Paging can be done either with the TMSI or IMSI of the mobile station. The network operator can define if paging will be repeated in the case in which the first paging is done with TMSI or IMSI and the MS is not found. If the paging is repeated, it is done with the IMSI. • The paging retry mechanism consists of two levels. On the one hand, the Visitor Location Register (VLR) requests the paging first with the Temporary Mobile Subscriber Identity (TMSI) and when there is no response, it can request the paging with the subscriber's International Mobile Subscriber Identity (IMSI). On the other hand, the Mobile Services Switching Centre (MSC) can repeat the paging over the A/Iu interface several times with the actual TMSI or IMSI. Soc Classification level 40 © Nokia Siemens Networks

IMSI paging Successful Paging With IMSI


Re-paging


Unsuccessful Paging With IMSI

Power Control


Power Control Motivation Reduced interference on DL/UL

Longer service time of battery Realization of power class

Activation of DL power control

powerCtrlEnabled Y,N Power control independent


for DL and UL for each call

Power Control Parameter Output Power Limits Maximum MS output power

Power Values

Power class dependent range

msTxPwrMaxGSM msTxPwrMaxGSM1x00 1800/1900 TCH msTxPwrMaxCCH msTxPwrMaxCCH1x00

5..39 dBm GSM 900 TCH 0..36/32,33 dBm GSM

5..39 dBm GSM 900 CCH 0..30 dBm GSM 1800 CCH 0..32 dBm GSM 1900 CCH

Minimum MS output power minMSTxPower

Attenuations 30 dB Range

5..39 dBm GSM 900 0..36 dBm GSM 1800 dBm GSM 1900 Maximum BTS output 0..32 power (by minimum attenuation) bsTxPwrMax bsTxPwrMax1x00

0..30 dB GSM 900 0..30 dB GSM 1800/1900

Minimum MS output power (by maximum attenuation) bsTxPowerMin Soc Classification level 45 © Nokia Siemens Networks

0..30 dB

Additional attenuation for super reuse TRx

Power Control Parameters Power Change Step Sizes Desired power level can be achieved in 1 or 2 commands

Yes

No

Fixed step size

Variable step size

Fixed increment step size powerIncrStepSize

2,4,6 dB

Fixed decrement step size powerDecrStepSize


2,4,6 dB

Power Control Strategy Triggering

Actual average samples

Nx samples Less than Px samples exceed threshold No power change triggered

threshold Signal level thresholds pcUpperThresholdLevelDL/UL pcLowerThresholdLevelDL/UL

-110..-47 dBm -110..-47 dBm

Signal quality thresholds pcUpperThresholdQualDL/UL pcLowerThresholdQualDL/UL Number of average samples Nx 1..32 Px 1..32 Soc Classification level 47


0..7 0..7

Nx samples Px samples exceed threshold Power change triggered Power change step size estimation

Power Control Strategy Scenarios


Exceeded threshold

Action

Reason

pcUpperThresholdLevelDL pcLowerThresholdLevelDL pcUpperThresholdLevelUL pcLowerThresholdLevelUL

BTS power decrease BTS power increase MS power decrease MS power increase

Signal level Signal level Signal level Signal level

pcUpperThresholdQualDL pcLowerThresholdQualDL pcUpperThresholdQualUL pcLowerThresholdQualUL

BTS power decrease BTS power increase MS power decrease MS power increase

Signal quality Signal quality Signal quality Signal quality

Power Increase Due to Signal Level Actual receive level RXLEV_DL/UL

pcLowerThresholdsLevelDL/UL Power control triggered UL: Power increase of MS DL: Power increase of BTS RXLEV_DL/UL > pcLowerThresholdLevelDL/UL - 2 powerIncrStepSize Yes Fixed step size

No Variable step size

PWR_INCR_STEP = powerIncrStepSize PWR_INCR_STEP = pcLowerThresholdLevelDL/UL – RXLEV_UL/DL Soc Classification level 49


Power Control Summary Upper Level

Lower Level

Upper Quality

Power increase Power decrease Power decrease 6 dB due to quality due to level due to level or quality

Power increase due to level

No action

Power decrease due to level

Lower Quality Power increase due to level or quality


Power increase due to quality

Power increase due to quality

Handover Control and Adjacencies


Intra cell ho MSC

BSC

BTS

MS Measurement Report ( SACCH )

Measurement Report/Result

3

1

2 PHYSICAL CONTEXT INFORMATION

Physical Context Request Physical Context Confirmed

4 NEW RESERVATION AND ACTIVATION

Channel Activation

5

Channel Activation Ack.

6

Assignment Command (FACCH )

7

SABM ( FACCH ) Establish Indication

9

SIGNALLING ON FACCH OLD

8

UA ( FACCH )

SIGNALLING ON FACCH NEW

10 Assignment Complete ( FACCH ) DT1 ( HO Performed )

15


13

Receiver Ready ( FACCH )

12 RF Channel Release RF Channel Release Ack.


HO MEASUREMENTS

14

11 OLD RELEASE

INTRA BSC HO MSC

BSC

BTS 2

BTS 1

MS

Measurement Report ( SACCH ) Measurement Report/Result

3

Channel Activation Channel Activation Ack.

5

2

TCH RESERVATION AND ACTIVATION IN BTS2

4 6 8

HO Command ( FACCH )

HO Access ( FACCH )

9

Establish Indication

11

12

17

15

14



SIGNALLING ON FACCH IN BTS2

13


RF Channel Release RF Channel Release Ack.

10

UA ( FACCH ) Handover Complete ( FACCH )

Handover Complete

7

SIGNALLING ON FACCH IN BTS1

Physical Info ( FACCH ) SABME ( FACCH )

16

HO MEASUREMENTS

Handover Command

Handover Detect

DT1 ( HO Performed )

1

18

TCH RELEASE IN BTS1

INTER BSC HO OR INTRA MSC HO MSC

DT1 CR

4

BSC1

BSC2

HO Required

BTS 1

Measurement Report/Result

3

2

Measurement Report ( SACCH HO ) 1 MEASUREMENTS AND DECISION

Channel Activation Channel Activation Ack .

CC HO_ Req.Ack HO Command

TCH RESERVATION AND ACTIVATION IN BSS2 HO Command ( FACCH )

9

HandoverDetect HO Detect

6

7 DT1 HandoverCommand HO Command

8

HO Access ( FACCH )

11

12

13

15

16

18

14

UA ( FACCH ) HandoverComplete ( FACCH )

HandoverComplete

10

Physical Info ( FACCH ) SABME ( FACCH )

Establish Indication

DT1

MS

HO_Request)

5

DT1

BTS 2

17


19

HO Complete 20 DT1

21

Clear Command

22

RF Channel Release RF Channel Release Ack .

DT1

Clear Complete

RSLD

(SCCP Released)

RLC

(SCCP Released Ack)


24


23

DISCONNECTION AND TCH RELEASE IN BSS1

Synchronized Handover Signalling MS

NETWORK ACTIVE CALL HANDO CMD HANDO ACC HANDO ACC HANDO ACC HANDO ACC

Old Channel, Old Cell

New Channel, New Cell

HANDO COM ACTIVE CALL

Original and target cells controlled by same BCF No timing advanced information required for MS Inter cell handover from one sector to another of same BTS Soc Classification level 55 © Nokia Siemens Networks

Handover Strategy Triggering

Actual average samples

Nx samples Less than Px samples exceed threshold No handover triggered

threshold Signal interference thresholds hoThresholdsInterferenceDL/UL

-110..-47 dBm

Signal quality thresholds hoThresholdsQualDL/UL

0..7

Signal level thresholds hoThresholdLevelDL/UL hoThresholdRapidLevelUL

-110..-47 dBm -110..-47 dBm

MS speed thresholds upper/lowerSpeedLimit 2km/h) Number of average samples Nx 1..32


0..255 (unit =

Nx samples Px samples exceed threshold handover triggered Target cell selection

Handover Strategy (Handover Reasons) Uplink Quality

Uplink Level

AV_RXQUAL_UL_H O AV_RXQUAL_DL_H O AV_RXLEV_UL_HO

Downlink Level

AV_RXLEV_DL_HO

MS Speed

AV_MS_SPEED

Timing Advance

AV_RANGE_HO

Downlink Quality

INTERFERENCE & QUALITY

LEVEL

THRESHOLD COMPARISON

MS SPEED

DISTANCE

RAPID FIELD DROP Adjacent Cells

AV_RXLEV_NCELL( n)

Others causes (NO TRESHOLD COMPARISON)

CHANNEL ADMINISTRATION

IMPERATIVE HO

DIRECTED RETRY

- Intelligent Underlay/Overlay (IUO) - Traffic Reason Handover (TRHO)

POWER BUDGET

- Direct Access to Desired Layer/Band (DADL/B) UMBRELLA Soc Classification level 57 © Nokia Siemens Networks

PERIODIC RX LEVEL CHECK

Handover Strategy (Standard Target Cell Ranking) Adjacent Cell Load Threshold Can be checked only for cells belonging to the same BSC as the serving one btsLoadThreshold 0..100 % Adjacent Cell Priority hoPriorityLevel

0..7

Overloaded Cell -> Reduction of Priority hoLoadFactor 0..7 Ranking (not for imperative and traffic reason handover) 1) Corrected priority a Cell b c 2) Cells with same priority -> RX level Overloaded? Priority hoLoadFactor Corrected priority Rx level

N/Y 4 2 4/2 -75

No cell overloaded A overloaded

-> priorities 4,3,3 -> cell list a,b,c -> priorities 2,3,3 -> cell list b,c,a


N 3 1 3 -80

N 3 1 3 -83

Handover Strategy (Decision due to RX level) Any kind of handover (except umbrella) 1a

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) – P) P depends on MS power class

Umbrella handover 1b

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)

Minimum allowed signal level for target cell rxLevMinCell hoLevelUmbrella


-110..-47 dBm -110..-47 dBm

any handover (except umbrella) umbrella handover

Rx Level Handover (Example) hoThresholdLevDL /Px: 1, Nx: 1 hoMarginLevel = 3 dB

enableHandoverMarginLevQual =Y BTS output power = Maximum Adjacent cells

= -95 dBm

Level Threshold is exceeded (bad_RxLevel) LEVEL HO

RX Level

-90

evaluation • Conditions 1a and 2b: AV_RXLEV_NCELL – AV_RXLEV_DL_HO > hoMarginLevel fulfilled

RX Level

Serving cell

-90 hoThresholdLevelDL

-95

-95 Adjacent cell(n) HO

100 Soc Classification level 60 © Nokia Siemens Networks

• If no adjacent -> HO Fail

Serving cell

t1

t2

3 dB

-100

t1

t2

Suitable target cell: RxLev(n)≥ RxLev+3dB

Handover Strategy (Decision due to Power Budget) General case 2a PBGT > hoMarginPBGT(n) PBGT = (msTxPwrMax - msTxPwrMax(n)) – (AV_RXLEV_DL_HO - AV_RXLEV_NCELL(n)) (btsTxPwrMax - BTS_TXPWR) Handover due to RX level, RX quality, distance and umbrella handover 2b PBGT > hoMarginLev/Qual(n) PBGT = (AV_RXLEV_NCELL(n) - AV_RXLEV_DL_HO) (btsTxPwrMax - BTS_TXPWR)

Power budget margin to prevent repeated handovers between adjacent cells hoMarginPBGT -24..63 dB general case RX level and RX quality margins to prevent repeated handovers between adjacent cells hoMarginQual -24..24 dB handover due to signal quality Soc Classification level 61 © hoMarginLevel Nokia Siemens Networks -24..24 dB handover due to signal level

Power Budget Handover (Example) Serving Cell:

Best Adjacent Cell:

AV_RXLEV_DL_HO = -90 dBm msTxPwrMax = 33 dBm BTS_TX_PWR = 42 dBm btsTxPwrMax = 42 dBm

AV_RXLEV_NCELL(n) = -80 dBm rxLevMinCell(n) = -99 dBm msTxPwrMax(n) = 33 dBm btsTxPwrMax = 42 dBm hoMarginPBGT(n) = 6 dB

1a

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) - msTxPwrMax) -80 dBm > -99 dBm + (33 dBm - 33 dBm) = -99 dBm fulfilled

2a

PBGT = (msTxPwrMax - msTxPwrMax(n)) – (AV_RXLEV_DL_HO - AV_RXLEV_NCELL(n)) (btsTxPwrMax - BTS_TXPWR) PBGT = (33dBm - 33dBm) - (-90 - (-80)) - (42dBm - 42dBm) = 10 dB > 6 dB PBGT > hoMarginPBGT(n) fulfilled


Interference Handover (Parameters) Thresholds hoThresholdsInterferenceDL/UL hoThresholdsQualDL/UL

-110..-47 dBm 0..7

Intra / inter cell handover hoPreferenceOrderInterDL/UL hopping hopping enableIntraHOInterDL/UL handover


INTRA

for network without frequency

INTER

for network with frequency

Y/N

required to enable intra cell

Interference Handover (Execution) AvRX level  hoThresholdsInterferenceDL/UL AND AvRX quality value  hoThresholdsQualDL/UL Ranking of adjacent cells enableHOMarginLevQual = Y

enableHOMarginLevQual = N

Check of adjacent cells with conditions 1a and 2b

Check of adjacent cells with conditions 1a and 2a

Suitable adjacent cell ? Yes Inter cell handover Soc Classification level 64 © Nokia Siemens Networks

No

If enabled Intra cell handover

Otherwise Handover failure

Interference Handover (Example) hoPreferenceOrderInterfDL = INTER enableHandoverMarginLevQual =Y Adjacent cells BTS output power = evaluation Maximum • Conditions 1a and 2b:

hoThresholdQualDL =4 /Px:4, Nx:6 hoThresholdInterferenceDL = -85 dBm /Px:1, Nx:1 hoMarginQual = 0 dB Threshold is BOTH the Quality and Interference exceeded (bad_RxQuality/good_RxLevel) INTERFERENCE HO

AV_RXLEV_NCELL – AV_RXLEV_DL_HO > hoMarginQual fulfilled Adjacent cell(n)

Adjacent cell(n) RX Level

RX Quality 2

Serving cell

Serving cell

3

-80

4

hoThresholdQualDL -85

• If no adjacent -> Intra HO

hoThresholdInterferenceDL

5

HO

6

t1


t2

Suitable HO target cell: RxLev(n)≥ RxLev

-90

t1

t2

RX Quality Handover (Execution) Thresholds hoThresholdsQualDL/UL

0..7

AvRX quality value  hoThresholdsQualDL/UL Ranking of adjacent cells enableHOMarginLevQual = Y

enableHOMarginLevQual = N

Check of adjacent cells with conditions 1a and 2b

Check of adjacent cells with conditions 1a and 2a

Suitable adjacent cell ? Yes Inter cell handover Soc Classification level 66 © Nokia Siemens Networks

No Handover failure

PARAMTERS & EFFECTS



RECOMMENDATION PARAMTERS – 2G Radio


Summary of parameters 

BTS Parameters - BLT, REO, MADR, MIDR, RE



HOC Parameters - IDR, IDN, IDP, IUN, IUP, LDR, LUR, LDW, LUW, QDW,QUW, EIH & EIC



POC Parameters - LDW, LUW, QDW, QUW, INT, LDR, LUR, LDN, LUN, UDR &



Adjacency Parameter SL to be implemented.



BSC Parameters - ITCF to be implemented.



Increase MFRMS– 4 to 5 in those few cell having Page deletion



RACH DELETION— -Lapd load increase from 32kbs to 64kbs-max load crossing the threshold limit.


UUR.

BTS PARAMETERS

HOC PARAMETERS


POC PARAMETERS

ADCE PARAMETERS


BSC PARAMETERS


Default, Specific and Sensitive Parameters 1. Default parameters •

BSC, BTS, HOC, POC, ADCE, TRX tables

Sensitive parameters • • • •

BTS table: HOP, BAR, PLMN, ACC, RXP, TLC, PMAX, DMAX, TRP, IDLE, ACT, RDIV POC table: PMAX, UDR, UUR, LDR, LUD HOC table: EPB, HPP, LDWS, LUWS, QDWS, QUWS, QDR, QDP, QDN, QUR, QUP, QUN, LDR, LDP, LDN, LUR, LUP, LUN, ADCE table: PMRG, LMRG, QMRG, MRGS

2. Specific parameters • • •

BTS table: BSC id, BCF id, SEG id, BTS id, BTS NAME, Cell id, MCC, MNC, LAC, RAC, NCC, BCC, MAL, HSN1, HSN2, MO, MS, CDEF, CDED ADCE table: BSC id, BTS id, N-LAC, N-Cell id, N-BCCH, N-NCC, N-BCC, synchronised TRX table: BSC id, BTS id, TRX id, FREQ, TSC, TSL configuration


73 © 2006 Nokia 08-11

1. Network Optimization Principles / 2006-

Synchronised handover • Non-synchronised Handover • MS sends access bursts (HO_ACCESS) (with varying TA) until it receives PHYSICAL_INFO

• Synchronised Handover • MS sends a few access bursts (HO_ACCESS) and then starts transmission with previous TA

• Non-synchronised handover leads to a longer communication interruption than synchronised handover (200ms vs. 100ms) • Synchronized HO should be activated between sectors of the same site. If activated on inter-site adjacencies the handover can fail

Synchronized HO

Non- Synchronized HO

Site A Soc Classification level 74 © Nokia Siemens Networks

Site B 74 © 2006 Nokia 08-11


Examples of wrong parameter set with impact on network operation/performance – call setup, qual, bands 1. No calls happening in a cell • • •

Cell Barred Non existent (LAC, Cell ID) in MSC DMAX = 0

2. Very few calls happening in a cell • •

RxLevAccesMin Wrong MNC, MCC, LAC declaration

3. Very low traffic in a cell •

msTxPwrMax = 0, bsTxPwrMax = 30

4. Bad quality in UL after rehoming 5. Few traffic in 1800 layer of a dual band 900/1800 network Soc Classification level 75 © Nokia Siemens Networks

75 © 2006 Nokia 08-11


Example 1a • No calls happening in a cell: The cell has been barred Handover

 Call Setup


76 © 2006 Nokia 08-11




Example 1b • No calls happening in a cell: CI different between MSC and BSC or non existent (LAC, Cell ID) in MSC


77 © 2006 Nokia 08-11

MSC does not find (LAC, CI) in its 1. Network Optimization Principles / 2006database

Example 1c • No calls happening in a cell: MsMaxDistanceInCallSetup (DMAX) = 0 Despite the coverage of the cell, no calls will be established!

DMAX = 0

Soc Classification level 78 © 2006 Nokia 1. Network Optimization Principles / 2006-0878 © Nokia Siemens Networks 11

Call Setup



RxLevel = -70 dBm

Example 2b • Very few calls happening in a cell: Wrong MNC, MCC, LAC declaration in network - MNC: 01 ≠ 1 !!! (In OSS correct value)


79 © 2006 Nokia 08-11


Example 3 • Very low traffic in a cell: msTxPwrMax = 0,

Parameter value bsTxPwrMax bsTxPwrMaxbsTxPwrMin = 30 minMsTxPower msTxPwrMax

Value_______Default 0 … 30 dB 0 … 30 dB 0 … 36 dBm 0 … 36 dBm

Attenuation Values (dB) BTS Max Power = BTS Power – (bsTxPwrMax = 0 dB) BTS Min Power = BTS Power – (bsTxPwrMin = 30 dB) Power Values (dBm) MS Max Power = (msTxPwrMax = 33 dB) MS Min Power = (minMsTxPower = 13 dB)


80 © 2006 Nokia 08-11


0 dB 30 dB 0 dB

Example 4 • Bad quality in UL after rehoming: DiversityUsed parameter not set to yes anymore

After rehoming RDIV parameter was set to default value (No) and UL quality was affected.


RDIV = Y

Uplink Diversity improves quality of signal received.

81 © 2006 Nokia 08-11


Example 5 • Few traffic in 1800 layer of a dual band 900/1800 network: Idle Mode: C2 parameters not set properly (temporaryOffset, penaltyTime)

BCCH

BCCH

slow moving mobile 1800: micro-Layer


82 © 2006 Nokia 08-11

fast moving mobile 900: macro-layer


Examples of wrong parameter set with impact on network operation/performance – upgrade 1. High drop call rate after upgrading a cell from 4 to 6 TRXs • Update MAL, no update of MAIO offset • TRXs with different power without ICE activated


83 © 2006 Nokia 08-11


Examples of wrong parameter set with impact on network operation/performance – upgrade 1. High drop call rate after upgrading a cell from 4 to 6 TRXs • Update MAL, no update of MAIO offset • TRXs with different power without ICE activated


84 © 2006 Nokia 08-11


Example 1a • High drop call rate after upgrading a cell from 4 to 6 TRXs: Update of the MAL with no update of the MAIO offset


85 © 2006 Nokia 08-11


Example 1b • High drop call rate after upgrading a cell from 4 to 6 TRXs: TRXs with different power without ICE activated Coverage BCCH - TRX

Capacity Traffic - TRX

MS in a region covered only by Coverage-TRX, ICE not activated. Result: BTS may allocate a TSL in Capacity TRX. Call will drop.


86 © 2006 Nokia 08-11


Example 1b • TRXs with different power TRX RF Units

TX RX

main div

+3dB

LNA

LNA

TX RX

main div

TX RX

main div

TX RX

main div

WBC LNA

WBC LNA


87 © 2006 Nokia 08-11

Duplexer

main div

Duplexer

TX RX

Duplexer

main div

X X X

Receive Multicouplers Dual Duplex Unit & Wideband Combiners Duplexer

TX RX

Antennas


TX/RX ant

X X X TX/RX-div ant

Examples of wrong parameter set with impact on network operation/performance – frequencies

1. Drop call rate increase after new frequency plan implementation • Double BA List activated

2. Impossibility to unlock some BTS after a RF-frequency hopping implementation

3. Impossibility to unlock some BTS after a frequency retune • NON-EDGE TRX, with GTRX = Y • TRX, with GTRX = Y, not attached to any EDAP pool 4. No handover happening after frequency retune between 2 cells from different BSCs • ADCE table has not been updated for other BSC


88 © 2006 Nokia 08-11


Example 1 •

Drop call rate increase after new frequency plan implementation: In the meantime, measurementBcchAllocation has been changed to idle and MA list defined with old BCCH frequency band OLD MA List BCCH

TCH

TCH

BCCH

TCH

OLD FREQUENCY PLAN

NEW FREQUENCY PLAN

These BCCH frequencies will not be measured by old MA Li These TCH frequencies will be wrongly measured


89 © 2006 Nokia 08-11


Example 4 • No handover happening after frequency retune between 2 cells from different BSCs: Frequency retune has been done with MML command. ADCE table has not been updated for incoming adjacencies TRX belonging to other BSCs BSC id

BTS id

TRX id

FREQ fA

N-Neighbour

fAB

Cell A

ADCE

Cell B

BSC id

BTS id

N-LAC

fA


N-Cell id N-BCCH fAB

90 © 2006 Nokia 08-11


Examples of wrong parameter set with impact on network operation/performance – Handover 1. No handover from a cell towards all its neighbours •

PLMN permitted = No

2. High Handover failures after implementation of new adjacency plan •

SYNC = YES

3. No handover happening from an interfered cell •

hoMarginQual set to 0

4. 100% of handover failures in an adjacency relation •

Co-BSIC co-BCCH declaration

5. High number of handovers •

hoThresholdsLevUL = hoThresholdsLevDL

6. Handover not happening when DL signal level of neighbour much greater than serving cell • POC DL activated Soc Classification level 91 © Nokia Siemens Networks

91 © 2006 Nokia 08-11


TIMERS



GSM TIMERS



RADIO RESOURCE TIMERS



RADIO RESOURCE TIMERS



TIMERS



IMP TIMERS –T8



T10



T3101



T3103



T3107



T200



General about T200 timer •

When the BTS transmits a DL layer-2 frame on the air (e.g. an I-frame with an embedded layer 3 message) the BTS starts the timer T200 and waits for the acknowledgement frame from the MS.

•

•

The acknowledgement frame can be another I-frame sent by the MS in the UL (if the MS has to transmit a layer-3 DTAP message anyway) as well as RECEIVE READY (RR) (if there is nothing to be transmitted on layer 3). If the acknowledgement from the MS is not received within T200 the transmission of the layer 2 frame is repeated and T200 restarted. The total number of repetitions is restricted to N200, a fixed value specified by GSM which depends on the control channel types: N200(SDCCH)=23, N200(SACCH)=5,

•

N200(FACCH/FR)=34, N200(FACCH/HR)=29

•

If T200 expires after the last layer 2 frame repetition the BTS sends an ERROR INDICATION with cause ‘T200 expired N200+1 times’ (followed by a RELEASE INDICATION) message to the BSC, which releases the associated resources.

T200s Retuning – Soc Classification level 103 © Nokia Siemens Networks

T200—Timer –BSC 94 •

•

ZEFO:

• • • • • • • • • • • • • • • •

BASE CONTROL FUNCTION BCF-0006 DATA SITE TYPE ............................ P - ULTRASITE ADMINISTRATIVE STATE ................. UNLOCKED OPERATIONAL STATE .................... WO

•

D-CHANNEL LINK SET 102 ............. OM006 WO-EX RX DIFFERENCE LIMIT ..........(RXDL).. 10 dB MASTER CLOCK BCF .............(MCBCF). -CLOCK SOURCE .................(CS).... -SYNCHRONIZATION ENABLED ......(SENA).. F SYNCHRONIZATION MODE .........(SM).... UNSYNCH FACCH LAPDM T200 .............(T200F). 0 (BCF PREDEFINED VALUES) SDCCH LAPDM T200 .............(T200S). 0 (BCF PREDEFINED VALUES) BTS UNDER THIS BCF ARE: SEG-0006 S268MRICK3 BTS-0006 SECTOR-006 S268MRICK3 ..... UNLOCKED


T200-LAB TEST



Error Indication: T200 expired •

This sub counter is triggered if the BSC receives an ERROR INDICATION with cause 'T200 expired N200+1 times' from the BTS.

• Explanation: Whenever the BTS transmits a layer 2 frame over the radio interface, it starts the timer T200 (see associated parameter in the command SET BTS PKGBTST) and waits for the corresponding layer 2 acknowledgement from the MS. If this acknowledgement is not received as long as T200 runs, the BTS repeats the transmission of the same layer 2 frame at the maximum N200 times every time T200 expires. N200 represents a fixed number of repetitions and depends on the type of radio channel (SDCCH, FACCH (FR), FACCH (HR) etc.). If after N200 repetitions the acknowledgement still has not been received from the MS the BTS sends an ERROR INDICATION with cause 'T200 expired N200+1 times' to the BSC.

•

Up to a certain degree the occurrence of these ERROR INDICATIONs is normal in every network as it indicates transmission problems on the radio interface possibly due to bad radio conditions for individual mobiles (mobiles roaming indoor or in tunnels etc.). In fact, in a normal network the counts for the ERROR INDICATIONs with this cause make up the biggest part of all ERROR INDICATIONs counted. However, excessive occurrence of these ERR INDs point to severe radio interface problems.


SDCCH Radio Failures- Vodafone Network EXAMPLE

SDCCH Radio Failures

300000

250000

200000

150000

100000

50000

0 12/1/2008

12/3/2008

12/5/2008

12/7/2008

sdcch_radio_fail

•T200s new value Implemented in test BSC •T200s new value implemented across network.

T200s Retuning – Soc Classification level 107 © Nokia Siemens Networks

12/9/2008

12/11/2008

sdcch_rf_old_ho

12/13/2008

12/15/2008

SDCCH Completion trend (BBH) – Vodafone Network EXAMPLE

100.00 98.00 96.00 94.00 92.00 90.00 88.00 86.00 84.00 82.00 80.00 78.00 MON

TUE

WED

THU

FRI

SAT

SUN

MON

1-Dec

2-Dec

3-Dec

4-Dec

5-Dec

6-Dec

7-Dec

8-Dec

TUE

WED

THU

FRI

SAT

SUN

MON

9-Dec 10-Dec 11-Dec 12-Dec 13-Dec 14-Dec 15-Dec 16-Dec

SDCCH Completion Rate (BBH) >=98%

•T200s new value Implemented in test BSC T200s Retuning

•T200s new value implemented across network.


TUE

Note : No Data on 3rd, 6th Dec08 due to OSS up gradation issues.

SDCCH Enhancement after timer LAPD T200 was fine-tuned appropriately from 0ms to 780ms ( sdcch)—IDEA NETWORK(NW Wide)

SDCCH DROP IMPROVEMENT

EXAMPLE 99.00

Timer --T200 implemented

97.50

97.02 96.25 96.50

96.00 94.45

94.50

SD DROP %

93.12 93.17 93.00

92.24

92.12

91.69

91.59 91.50 90.01 90.00

90.33 89.61

88.50 87.00 85.50

DATE Soc Classification level 109 © Nokia Siemens Networks

97.39

DAY 2.NETWORK PERFORMANCE OPTIMIZATION



KPI with Counters





GHOST CCCH RES Counter ID: 003030

Network element name: GHOST CCCH RES

Version: 2.1

NetAct name: GHOST_CCCH_RES

Description: Number of ghost reservations on a CCCH. See also counter 003031. Updated: When a ghost reservation is detected on a CCCH. This kind of random access can be caused, for example, by white noise or co-channel interference. Note that the ghosts triggering this counter have illegal establishment cause. Ghost accesses with legal establishment cause get on SDCCH and later fail typically causing the triggering of counter 0010075.



RACH REJECTIONS –ND 134





KPI- Rules, SDCCH Blocking SDCCH Blocking >X%

No

ND_211 ND_130 Cngt_2 Blck_5 Blck_5b

Case closed

ND_211 Check sdcch blocking. Can sdcch capacity be added without tch blocking

SDCCH blocking is high ND_139,ND_131 ND_130, uav_22 csf_1a,csf_11 Ava_45a

no

sdcch Blocking is still high

yes Yes Check unavailability in the cells, averarage available sdcch

Yes, make corrections

Yes, add sdcch capacity Availability OK

Is dynamic sddch active

No, activate Dynamic sdcch

ND_211 c1154

yes

No, check parameter Values and make corrections ND_211 c2032 Yes, remove combined sdcch

Yes, Optimize LU area border

No

Is dynamic sdcch reaching max values in some moment

yes

Is combined sdcch used

NetAct Planner P_nbcs_cc_pm

no

Is high sdcch traffic due to Location updates. If yes, can LU area be optimized? Check also PRAU parameter, can the value be increased?


No

Add TRX and add Sdcch capacity

BLOCKING—ND Report-182



SDCCH Blocking • SDCCH avalability

FM

– Check alarms (are TRXs & TSLs in Working State? ), check availability report and RxQuality report to verify whether there is a badly functioning TRX. Fix hardware problem. CM

• SDCCH capacity – Check actual SDCCH configuration ( e.g. Combined BCCH/SDCCH, Number of SDCCH channels). If there is insuficient SDCCH capacity and enough TCH capacity, add SDCCH TSL. Other solution e.g. PM are to add TRX, activate Dynamic SDCCH, activate FACCH Call Setup.

• SDCCH traffic – Verify traffic distribution (LU, SMS and MOC in %); – Cell is covering a region greater than planned. Verify TA statistics. May need to change DMAX, or downtilt. Soc Classification level 118 © Nokia Siemens Networks

118 08-11

© 2006 Nokia


SDCCH blocking • SDCCH traffic due to location updates – Bad location area setting (Check MCC, MNC and LAC parameters) – Bad Location area geographical configuration. Too small LA definition will cause many LA updates. Border of LA in a busy avenue will cause many LUs in both location areas! – Low value for CellReselectHysteresis – Low value of periodicTimerLU – Verify if downtilt is needed or an increase in SDCCH capacity (air and Abis interfaces).

• SDCCH traffic due to SMS – Increase SDCCH capacity (air and Abis interfaces). Change Request!


119 08-11

© 2006 Nokia


SD BLOCK ISSUES • • • • • • • • •

Look into the BSS BBH KPI Reports and find out the list of cells where there is SD congestion See the trend for at least 3 days to ensure that it was not due to any specific reason .if appears for one day then no issue Look into the SD configuration in that cell and try to have proper dimensioning as per the demand. Look into the A-ter status and also the site fluctuations or neighbour site not taking call .escalate the same to OMC and O&M team Look into the cell in LAC boundary andhavin lot of location update signaling due to high traffic flow in LAC boundaries , correct this thro proper optimization to have minimum overlap or introducing selection offset . Look into the coverage foot print and over shooting of the site thro TA report , optimize and ensure the neighbour cells sharing the SD demand for calls in that region. Look into the A-bis signaling load if possible for a high configuration site go for 64K PCM slot for LAP-D signaling thro OMC Engineer. NSS should ensure minimum call re-attempts thro proper POI dimensioning so that the SD usages will be less. Disable Direct retry in that cell and enable Traffic reason


HO.

Parameters & features – SD blocking •BSC parameter Dynamic Stand-alone Dedicated Control Channel (SDCCH) enables the configuration of SDCCH resources according to the actual SDCCH traffic situation of a cell. When the BTS temporarily needs larger SDCCH capacity than normally, the BSC configures idle traffic channel (TCH) resources for SDCCH use. When the SDCCH congestion situation is over, the extra SDCCH resources are configured back to the TCH resources

Overview of FACCH Call Set-up When an MS requests a dedicated resource by sending a random access, the BSC tries to allocate an SDCCH for the MS. If there are no SDCCHs available at that moment, the BSC tries to allocate a TCH instead of rejecting the resource request. If there are free TCHs, FACCH Call Set-up is used to assign the MS from the CCCH to the TCH instead of the SDCCH - with the immediate assignment procedure. The FACCH is used for call set-up signalling instead of the SDCCH. The TCH is used for signalling and thus no assignment procedure is needed in the radio interface. Instead, only the mode modify procedure is required to change the channel mode from signalling to, for example, speech or data.





KPI- Rules, SDCCH Drop

ND_166

SD DCR > 2% and SD DCRnum > 10

Yes

Drops due to RF Reasons

No

Drops due to Abis Reasons

No

Drops due to A-interface Reasons

No

Drops due to other Reasons

Yes

Yes

Yes

Yes

RF

Abis

A

Other

No No


Case Closed

KPI- Rules, SDCCH Drop (RF) P_nbsc_RX_Statistics, Counter (q0...q7)ul and dl all levels ND_204,c1003

RF drops

Yes

Check RX Statistic,qquality level distribution. Any signal level problems = samples in bad signal leve <-100dBm

P_nbsc_RX_Statistics,( q0..q7) <100dBm P_nbsc_Link_balance ND_191, ND_195

YES Check TRX, Combiners, configuarions, diversity and power parameters

P_nbsc_RX_Statistics, Counter (q0...q7)ul and dl all levels ND_204 Check RX Statistic,qquality level distribution. Any Bad Quality problems = Lots of samples in good signal level and bad quality

No

P_nbsc_RX_ Statistics, ND_204

No

No

No

SDDCR still too high

All Alarms are checked and abis trace is done

Yes

SDDCR still too high

Yes

Yes YES, Change the TRX / combiner

TRX is broken (sample distribution is somehow strange, for example only quality 4 samples)

Investigate alarms. If problems are not solved, activate abis trace

Any balance problems between UL and DL.

Any Improvements

No

No

Check that power control parameters UL / DL are correct

No

Change new frequency based on interference matrix If The trace was not long enough, activate another trace

Optimizer, NetAct Planner

Correct

Signal level problems. Improve signal level

Yes

Add -new site -lna -new sector -more gain antenna Yes

Activate

Investigate log files. Check DX causes See doc Call related DX causes in BSC,

Trace has been measured long enough. Any problems found

Make corrections


No

alarms

Yes

PoC parameters

Not Correct Make corrections

Case Closed

Trace was long enough, not any problem was found

KPI- Rules, SDCCH Drop (abis) Abis >X%

P_nbsc_RX_Statistics, Counter (q0...q7)ul and dl all levels ND_204

P_nbsc_rx_statistics

P_nbsc_traffic Counters(1072-1080)

Check abis drops.Is the main reason sdcch_abis_fail_call

Check RX Statistic table or ND report 204, UL/DL level distribution. Any Bad Level problems = samples in bad signal level

No

Yes Any Improvements

No

Yes

P_nbsc_servi ce, counter 57020

Check t3101 expired, is the value almost same as sdcch_abis_fail_call

Yes

No

Has any parameter changes done

Yes

No


Adjust rx_lev_access_min rx_lev_min_cell values little lower. Caution, This can increase TCH Drops.

No Yes, Check TRX, Combiners, Configurations, Diversity and Power settings. Make corrections

Yes NetAct Planner Yes, change bsic

No

Check RX Statistic quality/ level distribution. Any Bad Quality problems = Lots of samples in good signal level and bad quality

Any balance problems between ul and dl. Check ND 195, ND 191 or link balance table

Check Co BSIC + BCCH problems, any site with same BSIC + BCCH is existing < 50km

Yes, Change TRX

No No Yes

No

ND_131,ND_139

Yes, unlock TRX’s

Any availability problems. Check sdcch availability

No

Not Correct Make corrections

Check that power control parameters UL / DL are correct

Change new frequency based on interference matrix

Optimizer, NetAct Planner

Correct Yes, Try to Reduce overlapping Over borders etc. Tilting? Rehoming can Sometimes helps, if areas Are not optimized

No C3030 Check ghost reservations, c3030 values. Is this the main reason

Yes, see Interference analysis

Options: -add site, sector -add lna -change antenna type

Signal level problems. Improve signal level

Case Closed No

Check if cells are located near LA border more sdcch traffic


Yes

No

Still Abis drops and problems

KPI- Rules, SDCCH Drop (A) alarms

A interface problems. Alarms are checked and A interface trace is done

A >X%

Yes

No

Repair ET lines

No Alarms Are Solved

Any improvements

Investigate alarms.If problems are not solved, activate A trace

Trace was Long enough. Not An problem was found

Investigate log Trace files. Check DX causes, see was document Call not long related DX causes in BSC enough

Any problems found. Trace was long enough

Make corrections


No

Still A drops or problems

No

Yes

Case Closed

No Activate

Check ET lines in the BSC and transcoders /TCSM. Any problems

Yes

Yes

KPI- Rules, SDCCH Drop (other)

Other

Case Closed

Check all the alarms

Lapd fails

No

Yes

signalling fails or PCM fails. Check transmissio / parameters

BTS fails

No

No

User Act, bcsu, resets

Yes

Yes

Yes

TRX or BTS fails. Check that BTS/ TRX are working properly

Configuration problems, check configurations Yes


Netw Act Fails

Resets or act fail channel failures

No

No

Still lots of other drops

SDCCH Drop • Ghost SDCCH – Double-Access /Multiple reservations due to co-Bsic, co-BCCH. Check and improve frequency plan. – RACH retransmissions/Multiple reservations due to bad coverage or interference and high numberOfRachRetransmissions. Lower RACH retransmission parameter value. Check and improve frequency plan and/or downtilt. – RACH retransmissions/Multiple reservations due to mass paging deleted. During festivals/ holidays/ concerts many subscribers are located at the same LAC, paging and rach load increases considerably. Consider LAC optimization, Abis expansion, paging group optimization, reduce paging repeat & rach retransmission times during busy hour. CM • Radio Fails FM – Check alarms and RxQuality report to verify whether there is a badly functioning TRX. Fix hardware problem. Check antenna line.


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SDCCH Drop • Radio Fails (cont.) – Coverage. Verify TA report and planning tool. – Interference. Check Frequency Plan. Solution e.g. add sites, downtilt antennas, increase RxLevAccessMin. PM – Extended coverage of cells in location area borders. Check LU parameters and/or downtilt

• 100% ABIS Fails – Failure in BTS software (BCSU reset in BSC).

Change Request!

• 100% AIF Fails – BTS connected to other BSC or BTS is not declared in MSC.


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ND REPORT__SD DROP--166



SDCH DROP Issues • • • •

•

•

Check the High SD drop Cells from the BSS KPI reports Look into the Drop Reason whether it is due to RF fail or any HW reason or any Signaling issue .If HW, site fluctuation or Signaling issue escalate the same to O&M/OMC team for rectification Check the proper A-bis link PCM mapping and signaling channel definition thro OMC engineer. Look into the coverage foot print of the same thro TA report and the site Data base if the cell is overshooting to longer distances optimize the same . If SD is configured in BCH carrier then look for the C/I condition for the BCH carrier looking into the reuse patterns. If SD is configured in Hopping TRX then look into the TRX performance and bad samples in that TRX and check the VSWR/Antenna /Combiner connections to the TRX .U can get a hint if you look at the assignment success ration of the cell. Look into the Quality samples in the TRX in which the SD is configured if the TRX is faulty replace the same at the earliest .

• • • • •

Try to reduce the SD usages and reduce the SD load of the cell thro proper optimization. Look into the signaling TS load on A-bis link and try to reduce the same by reconfiguration of PCM slots Check the Rx.P Value set to the cell , Make it -104 dBm . Ensure the T-200 value set to 780 mSec in all cells Correct the SD dimensioning so that there will be minimum no of dynamic SD allocations on TCH .

•

Following the procedures defined above and taking corrective action in time will result into a Quality network with SD DROP KPI maintained


PATH BALANCE—208



Parameter and features 1. BTS : Antenna Hopping, HYS



Path balance --208 Case1: Jumper from TRX 4 to combiner loose (check connectors at both ends)

Case2: Jumper from Duplexer to TRX 4 (check connectors at both ends)

Case3: Check common feederline from Top of cabinet to Antenna port ( loose connector’s at either end or High VSWR problem, TRX 2&4 in this case use the same feeder) In this case, the Path imbalance (DL-UL) varies between +1.6 to -4dB which doesn’t tell much BUT DL pathloss variations between TRX’s is from 112.8 to 136dB & UL pathloss variations between TRX’s is from 111.2 to 140dB DEFINITELY A PROBLEM! Soc Classification level 134 © Nokia Siemens Networks

134

© 2005 Nokia

V1-Filename.ppt / yyyy-mm-dd / Initials

Use OSS Data to identify & pinpoint HW faults faster Sector A

Path Balance Reports help understand any imbalance between UL and DL

80.00

Whereas

70.00 60.00 50.00

TRX3 TRX4

40.00

TRX5

Eg.Pathloss comparisons between TRX’s of same sector can help identify loose cables or hardware faults, taking other TRX’s as reference case

TRX6

30.00 20.00

Eg. In Sector A:TRX 3 &4 have only 20% of DL SS samples <-100dBm whereas TRX 5 & 6 have 70% of their DL SS samples <-100dBm.

10.00 0.00 >70dBm

70-80dBm

80-90

90-100dBm

<100dBm

Downlink Signal Strength

Prob:1 Combiner Faulty Sector B

In Sector B TRX 5 clearly had a difference in signal strength only in Uplink.

120.00 100.00

Prob: Rx cable found to be loose

80.00 TRX3 60.00

TRX4 TRX5

40.00 20.00 0.00 >70dBm

70-80dBm

80-90

90-100dBm

Uplink Signal Strength


135

© 2005 Nokia

<100dBm

The same faults can also be seen using Rxlevel statistics from OSS shown in this slide, but 208 is faster for analysis!


How to identify the worst cells in your network? • • • • • •

Import DL & UL pathlosses for all TRX’s of all cells into separate columns Use a pivot table to get Min and Max values of dL and Ul pathlosses in a cell Identify all cells with DL TRX pathloss variatons >10dB(for a NW with huge TI quality issues , sstart with 15dB) The same can be done for UL also A combined analyses for DL& UL with >10dB diff gave a list of 58 cells for UP(West) attached below. Go back to 208 report for detailed analysis


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KPI- Rules, TCH Blocking Blck_8i Trf_1d ND_135 ND_138 ND_139 ND_211

TCH Blocking >X%

No

Case closed

TCH blocking is high

No

Planner, Optmizer ND_072

yes Yes. Check block Trend if it will drop after event

Block due to any events near ?

Check if there are some missing neighbours

Have you checked all capacity features

No

Yes

Tch Blocking is still high

No

Uav_15a ND_139

Yes Yes, make corrections

Check unavailability in the cells, also from adjacent cells Yes, add neighbours Availability OK

alarms Yes, corrections

No

No All correct

Yes,Change broken components

Check RX statistics if there are cells with broken TRX. Alarms are not always sent

NetAct,POC

No broken components

Are POC parameter correct, check also adjacent cells


No, optimize dual Band network traffic handling parameters, AUCL(umbrella) Common BCCH param

Add TRX

ND_211

Are there some broken cells, check alarms, also Adjacent cells

P_nbsc_rx_statistics Counter (q0..q7)ul and dl

Make corrections

No. active HR and adjust Parameters Check also Dual Rate Timeslots and if Possible , change TCHF¨ To TCHD

Is Half Rate used and parameter optimized

yes yes

ND_211 Is dual band network optimized

TCH BLOCKING—182-ND REPORT



TCH blocking •

FM

TCH availability

• Check alarms (are TRXs & TSLs in Working State? ), check availability report and RxQuality report to verify whether there is a badly functioning TRX. Make Loop Tests on TRX. Fix hardware problem.

•

TCH capacity

• Bad TCH capacity dimensioning. Check number of TRXs.


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CM

TCH blocking •

PM

TCH traffic

• Cell is covering a region greater than planned. Verify TA statistics. Change DMAX, or downtilt. • High traffic in some cells. Solution .eg.: Quality degradation Add Macrocells Add Microcells Add TRXs with new freq Add TRXs without new freq Activate Directed Retry Activate Queuing Activate HR Activate AMR-HR Activate DADL/B Activate AMH Activate C2 parameter Modify hoMarginPBGT


143 08-11

no no no no/yes (IUO, FH) no/yes yes yes no no/yes no/yes yes yes

© 2006 Nokia

Change Request!


Decongestion and TCH blocking Issues

•

Check the BBH KPI report and find out the cells having utilization more than 90% .

•

Check the blocked TRX report 111 and if TRX blocked found, follow up with O&M team to rectify the same as soon as possible.

•

Look into the A-ter /TRAU status of the BSC in which the congested cell is integrated

•

Look into the GPRS and SD configuration and their usages in the congested cell ,Try to reduce the same and obtain more TS for TCH.

•

Check the site location along with any site nearby to share the traffic and look into the TA report 232 for the coverage foot print of the congested cell, if possible reduce the coverage foot print and let the neighbour cell to share the traffic thro proper optimization

• •

. If decongestion is not possible with the optimization of the nearest site look into the MA list and Fractional Frequency loading(20% in multiple site areas and 30% in single site areas) if any scope for TRX addition is there go for TRX expansion and ensure the MAIO changes properly to avoid co. and adj. channel hitting.


•Suggestion ,in multiple site areas first go for nearest low utilized sites optimization to share the traffic from the congested cells and after doing the optimization introduce the Traffic reason HO or Direct Retry between the neighbours . •FRL of 20% and FRU limit of 40% for HR call are allowed to avoid blocking go ahead for the same in TCH blocking cells. Suggestion : If SD block is there in cells never go for Direct Retry between the neighbours better go for Traffic reason HO with the neighbouring cells of the congested cell. •For single site areas if there is spectrum issue we should look for the customized MA list by adding some BCCH carriers carefully looking into BCCH reuse pattern in neighbouring cells and their presence close to the site •If we are unable to add TRX due to Spectrum limitation propose for a new capacity site to share the traffic .

Following the procedures defined above and taking corrective action in time will result into a Quality network with Utilization and blocking KPI maintained


Parameters & features 1. 2. 3. 4. 5. 6.

BTS PARAMTER: Directed Retry , FRL & FRU , TRHO, BLT, LSEG, Queuing





ASSIGNMENT FAILURES • •

• • •

Look into the BSS BBH KPI reports for High Assignment failure cells Mostly due to HW issues like : TRX faulty, TS issues , Wrong Combiner ,Antenna connections, Wrong Air combing antenna positions , TRX cable loose, VSWR issues ,Wrong PCM mapping ,TRAU issue, Site Fluctuations, Abis link BER . Escalate to O&M and OMC team to rectify the same and follow up till got rectified RF issues : High Coverage foot print of the site , High Dense clutter ,Wrong Antenna positioning . Needs optimization and site visit IMPACT ; High assignment failures in cells contributes to Call drop , HOSR failures, SD drops in dynamic SD , Low call volume etc etc .




KPI- Rules, TCH Drop Call Ratios Dcr_3j TCH DROPS AFTER SEIZURE TCH_RADIO_FAIL /c1013 +TCH_RF_OLD_HO /c1014 +TCH_ABIS_FAIL_CALL /c1084 +TCH_ABIS_FAIL_OLD /c1085 +TCH_A_IF_FAIL_CALL /c1087 +TCH_A_IF_FAIL_OLD /c1088 +TCH_TR_FAIL /c1029 +TCH_TR_FAIL_OLD /c1030 +TCH_LAPD_FAIL /c1046 +TCH_BTS_FAIL /c1047 +TCH_USER_ACT /c1048 +TCH_BCSU_RESET /c1049 +TCH_NETW_ACT /c1050 +TCH_ACT_FAIL_CALL /c1081 -tch_re_est_assign

Dcr_8h Dcr_5a

TCH DROPS AFTER ASSIGNMENT tch_new_call_assign /c57033 +tch_ho_assign /c57034 -tch_norm_release -tch_ho_release

/c57035 /c57036

-tch_re_est_assign

/c57032

CONVERSATION DROPS dropped_calls /c57007

/c57032 (S7)

DROPS 100 * TCH SEIZURES FOR NEW CALL tch_norm_seiz /c1009 +tch_seiz_due_sdcch_con /c1099 (S5) +msc_i_sdcch_tch /c4044 +bsc_i_sdcch_tch /c4057 +cell_sdcch_tch /c4074 -tch_succ_seiz_for_dir_acc /c1165 (S7)

-tch_re_est_assign

% CALLS

TCH ASSIGNMENTS FOR NEW CALL tch_new_call_assign /c57033

-tch_re_est_assign

/c57032

STARTED CONVERSATIONS conver_started /c57015 - msc_i_tch_tch /c4043

TCH RELEASE

/c57032 (S7)

CONVERSATION STARTED

Disconnect from MS

conn_ack to BTS

TCH SEIZED BSC allocates a TCH as a response to TCH request (Channel Activation)

TCH ASSIGNED Assignment_complete from BTS

RF CHN RELEASE Soc Classification level 150 © Nokia Siemens Networks

Rf_channel_release_ack from BTS

MS

BTS

csf_13

BSC

MSC

SDCCH signalling up to TCH seizure Authentication_Request

Authentication_Response

Authentication_Request

Authentication_Response Identification_Request

Identification_Request

Identification_Response

Identification_Response Encryption_Command

Ciphering_Mode_Command

Ciphering_Mode_Command

Ciphering_Mode_Complete

Ciphering_Mode_Complete

Setup

Setup

Call_Proceeding

Call_Proceeding

TCH DROPS AFTER SEIZURE Physical_Context_Requ Assignment_Request TCH_RADIO_FAIL /c1013 est +TCH_RF_OLD_HO /c1014 Physical_Context_Confirmation Start T9108 +TCH_ABIS_FAIL_CALL /c1084 Stop T9108 (TA info) +TCH_ABIS_FAIL_OLD /c1085 csf_14 drops after this point 57028 TCH_CALL_REQ, 57030 SERVED_TCH_CALL_REQ, 57031 SER +TCH_A_IF_FAIL_CALL /c1087 Channel_Activation +TCH_A_IF_FAIL_OLD /c1088 +TCH_TR_FAIL /c1029 Start T9103 +TCH_TR_FAIL_OLD /c1030 Channel_Activation_Ack +TCH_LAPD_FAIL /c1046 Stop T9103 Assignment_Command (SDCCH) +TCH_BTS_FAIL /c1047 Assignment_Command Start +TCH_USER_ACT /c1048 T10,T3107 +TCH_BCSU_RESET /c1049 TCH seized +TCH_NETW_ACT /c1050 +TCH_ACT_FAIL_CALL /c1081

csf_15

SDCCH signalling: MS moves on TCH, SDCCH released

Start T200

SABM (FACCH)

Stop T200

UA (FACCH)

Establish_Indication

Assignment_Complete (FACCH)

MS on TCH TCH DROPS AFTER ASSIGNMENT (Connection Failure from BTS, DX cause >= 300) spare057044 /c57044 (S10.5) drop_after_TCH_assign c1202 Soc Classification level (S11) 151 © Nokia Siemens Networks

Assignment_Complete Stop T10,T3107 Assignment_Complete

drops after this point

Dcr_8e

TCH DROP-ND REPORT—(163)



TCH DROP—KPI REPORT



KPI- Rules, TCH Drop

ND_163

DCR > X% and DCRnum > XX

Yes

No


Drops due to RF Reasons

No

Drops due to Abis Reasons

No

Drops due to A-interface Reasons

No

Drops due to Transcoder Reasons

No

Drops due to other Reasons

Yes

Yes

Yes

Yes

Yes

RF

Abis

A

TR

Other

Case Closed

No

KPI- Rules, TCH Drop (RF)

RF drops >X% >X count

Yes

Check quality/level distribution. Any Bad Quality problems = Lots of samples in good signal level and bad quality

Case Closed

Check quality/level distribution. Any Bad Level problems = Lots of samples in bad signal level

No

OSS, BTS,Cell parameters

P_nbsc_HO_adj Hfr_58,hfr_59

P_nbsc_RX_Statistics Counters(ul0..ul7,dl0..dl8) ND_204

P_nbsc_RX_Statistics Counters(ul0..ul7,dl0..dl8) ND_204

Check HOs to adjacent cells, Any bad HO problems to any adjacent cells?

No

No

Check cell parameters, discrepancies?

Yes Yes Yes

Yes

Yes, change -TRX -Combiner -broken antenna


Yes, Change TRX / Combiner

TRX / combiner is broken, for example only <100dBm level samples

Check TA statistics and Check all Neighbors. If lots of long distance samples and only nearest cells are neighbors, may be some neighbor cells are missing

Neighbors are missing No Change new frequency based on interference matrix

-Add LNA -Add new site -Add new sector

No

P_nbsc_power,Timing advance ND_232

Yes, Add neighbors

Signal level problems. Improve coverage

No

Check all HO parameters, any HOC parameter problems?

NetAct Planner, Optimizer

Make parameter corrections

Yes, Change parameters

OSS, Hoc parameters

No

Check blocking in target cells. If blocking, add capacity to Yes, add blocked cells capacity

P_nbsc_HO_adj Blck_19,blck_20

No Blocking Check if HO fails are due to MSC/ BSC border. If bad values, check borders. OptimizeMSC/ BSC borders


Yes

ND_150

No

alarms


No

DCR still too high

KPI- Rules, TCH Drop (abis) Abis >X% >X count

Drops are checked and Not real Abis problems

P_nbsc_CC_PM All counters

Case Closed

No

alarms

All Alarms are checked and abis trace is done

Yes

No

alarms

check the BTS release and the timer 3109 expired values. >BTS version 6.1 3109 expires in a BSC while waiting for the Release indication.These are seen as abis drops.These are not real drop not real abis problems

Yes

Alarms Are solved

Any improvements

Investigate alarms. If problems are not solved, activate abis trace

No

No

activate

BTS configurations, Pafile

Investigate log files.

Make corrections

Drops are happening in the release phase

Check CC table, which phase drops are happening

If not long enough, activate another trace

Trace has been measured long enough. Any problems found

Soc Classification level Yes 156 © Nokia Siemens Networks

Yes

No

Check the parameters related to abis. BSC parameters

OSS, BSC parameters Yes

Still high drops in Abis interface

KPI- Rules, TCH Drop (A) Alarms

A interface problems. Alarms are checked and A interface trace is done

A >X% >X count

No

Any improvements

Yes

Check ET lines in the BSC and transcoders /TCSM. Any problems

No

Yes

Yes Check that A parameter values are correct

Investigate alarms.If problems are not solved, activate A trace

No

Are parameters and timers checked

No

Repair ET lines

No Alarms Are Solved

MML commands P_nbsc_et_bsc P_nbsc_et_tcsm All counters

Activate

ZNRI:NA0; ZNNI:1,C;

Check that A timer values are correct

ZNMI:C; Investigate log files.

Trace was Long enough. Not An problem was found

Check if there are

Check that sccp counter values are correct

Trace errors, when MSC assign some pools was not long enough Make corrections

Any protocol error unspecified? Check bug possibility

Any problems found. Trace was long enough

Make corrections


Yes

Yes

ZOCI:1;

Still A drops or problems

No

Case Closed

KPI- Rules, TCH Drop (TR) Case Closed Alarms

TR >X% >Xcount

P_nbsc_CC_PM All counters ND_523, ICTF parameter

ND_247

TR problems. Alarms are checked

Check CC table, in which phase TR drops are happening

Yes

Not In Release Phase

Check TR codec specific fails, run

Done

Check TCSM statistics Done No

No

If release phase, not real In release phase drops

Yes Investigate alarms.If problems are not solved, activate abis trace (remote TR failures

Alarms are solved

Any Improvements

No

Trace Was not Long enough

Not done

Investigate

Investigate log files.Check if Trace failures are following some was long PCM either in Abis or A and enough, No fix accordingly. Before Implementing HR in the BSC Any problem was found & cells it is must to reconfigure the A interfacelinks to support Dual Rate. Otherwise it will give rise to high call failures mainly TCH_TR_fail due to mismatch of coding between TCH in Radio & "A" interface.

Make corrections Any problems found


Check that TR parameters are correct. If not, correct these

Yes

If drops are happening in some specific codec HR/FR issue investigate or is it more like individual TR problem

Not done If there some problems with TCSM investigate. ICTF, how many fails are ignored

Still TR drops or problems

KPI- Rules, TCH Drop (Other)

Other

Case Closed


Lapd fails

No

Yes

signalling fails or PCM fails. Check transmissio / parameters

BTS fails

No

No

User Act, bcsu, act fails

Yes

Yes

Yes

TRX or BTS fails. Check that BTS/ TRX are working properly

Configuration problems, check configurations Yes


Netw Act Fails

Resets or act fail channel failures

No

No

Still lots of other drops

TCH Drop and Corrective action • •

Non RF drops : Check the TCH drop reason in BBH stats report. Non RF drops may have two reasons one is TR drop and other A-bis fail . If you find such issues in a site/cell then escalate to O&M team and do continuous follow up till the same got corrected. Hint : If all cells or a single cell in a site is having TR drops then check the PCM mapping and the link stability . If most of the cells /sites in a BSC is having TR drops High then escalate the same to OMC to check TRAU block . For A-bis drop, it is the link or the E1/T1 card which may have issues or any issue in the internal wiring of the BTS .

•

RF Drops : 1. If RF drop is high in cells first step is to check the Air interface clearance (BCCH reuse pattern and C/I, and the database for Hopping, Over shooting sites, neighbour missing and neighbour definitions , call dragging due to congestion in neighbour cells, border cells, VSWR issues or TRX wrong connections). Try to minimize the Overlapping to reduce the co channel hitting and quick HO attempts .

Corrective action : See the path balance reports (208) to find out the VSWR issues , see to the assignment issues in those cells, analyze the neighbour cells resource availability during BBH to take the HO request , Look into the BCCH reuse in the coverage area of the cell , check the overshooting of the cell to longer distances and try to reduce the same thro optimization, check the Hopping pool MA List and MAIO and try to have best offset to avoid co.and adj. interference.Check Fractional Frequency loading in the cell ,restrict over shooting cells( This can be checked thro the report (196) which will give you a clear indication of bad samples and confirms if all TRXs are having bad samples during BBH ) .


2. Another reason for RF drop may be due to HW faults in BTS ,like TRX having poor quality TS , wrong antenna connections ,VSWR Issues in sites Corrective action : Check the assignment success rates in those cells where drop rate is high this will give you hint about the wrong connections of the devices ,Antennas . Look into the TRX Quality reports (196) where you can look into the poor quality samples per TRX if some TRX is having high poor UL/DL quality samples and others in the same cells are having good samples then the particular TRX is having some issue ,replace the same thro O&M team 3. Minimize the Hand Over attempts between cells by minimizing the overlapping of source and target cells and also setting the margins and Ping pong rejection timers . 4. Ensure the RLT and ARLT (in AMR environment ) is properly set guidelines we can set RLT 24 Frames and ARLT 36 Frames )

4. If all above you are finding ok still there is high RF drops then have a drive test and site audit to find out any external interference or Antenna issues in field ,check the VSWR thro O&M team . Following the procedures defined above and taking corrective action in time will result into a Quality network with Drop KPI maintained .


Parameters & features 1. B TS parameter :Antenna Hopping,;;DMAX,;;STIRC;;BFG 2. BSC parameter:ITCF 3. MSC parameter : Call Re establishment 4. Features : AMR PPC, ROBUST AMR





KPI- Rules, HO fail HO Fail

No

Case closed

No

ND_150 ND_153 ND_157

Ho fail is high ND_150 ND_153 ND_150 ND_153 ND_157 Yes, add Capacity, TRX

Check if fails are MSC incoming or MSC outgoing fails

yes

Yes, add neighbours

Check if fails are BSC incoming or BSC outgoing fails

No

No

Check if HO fails are due to blocking HOC

NetAct Planner Optimizer

ND_150 ND_153

Yes

HOC

P_nbsc_RX_st atistics

Yes

Check if HO fails are due to missing neighbours

No, optimize parameters NetAct Planner

Check if adjacent with high fail% are working properly

Are HO parameters correct

No

Optimize MSC / BSC borders

No, optimize HO parameters NetAct Planner

Are HO parameters correct

Yes Change Frequency

Yes Optimize dominance areas, overlapping, overshooting

There are interference in some TSL’s

Any Bad interference in adjacent cells

No interfer

Yes, improve coverage Any bad signal level -new site or LNA problems -New sector -More gain antenna Yes, change These broken No components P_nbsc_rx_statistics alarms Any broken components No, all cells are OK Yes


There are interference in some Frequency

P_nbsc_power _control



yes

No blocking

No

Yes, change Frequency or Tilt interferer cells

Check if fails are Intra HO Fails

No

Ho fail is still high

HO FAILURE REPORT—ND (153)



HANDOVER ANALYSIS



HO CAUSES –BSC WISE



HO CAUSES—CELL WISE--154



POOR HOSR • • • • • • • • • • •

Look into the 153 report for HOSR between source and target cells List all the neighbours where there is poor HOSR See the sites are performing well and there is no assignment failure issues and TRX HW issues Look into the BCCH and BSIC reuse pattern of the neighbours to ensure good C/I of the BCCH carrier and their definition in neighbour. Do the neighbour audit and check all the neighbours defined with proper database and LAC etc etc Define Sync neighbours between cells in a single site Check the Signaling load on A-bis and A-ter Thro Neighbour audit remove all neighbours which are not with level to retain the call and add all missing neighbours. Check the HO parameters and margins ,rescue hand over settings ,penalty timers from ZEAO and ZEHO logs to ensure less attempts and enhnace the success rate Check the whether Clock shift –DAC ( 1800-2400 ) Check Software mis match( BSC and BTS end


If AMR enabled ,NSS team should ensure Proper dimensioning and A-ter link availability for codecs in TRAU . Optimize the Overlap areas between cells to have minimum HO requests in each call . Decongest the target cells to ensure TCH resource availability for a HO request . Try to introduce more Ho margin between cells inter BSC to have less attempts for Inter BSC HO . Allow RX Lev HO between single sites and minimum overlapping neighbours , with a very less HO Margin and penalty timer In an AMR scenario to minimize the quality HO ensure the Threshold level for Quality HO is set RX qual 5 or 6 . Poor HOSR Impact: Enhances TCH drop, TCH Block due to poor mobility management between sites.

Concentrating on reports and following the procedures defined above and taking corrective action in time will result into a Quality network with all KPIs maintained


Paramters and features BTS Parameter : SL, PRI,PMRG,LMRG,QMRG, HO parameter : MIU,MIH,HPP;;QDR & QUR;;LDR & LUR;;LAR & LER;C/I estimation method BCF parameter : DAC drift

MSC : LAC Mismatch

AMR : IHRH & IHRF,SAL;;;n(x),p(x) change for QDRF & QURF



RX QUALITY 100* (sum of RxQual samples 0-5)/sum of all RxQual samples 0-7)



Rx Quality

DL/UL CUMULATIVE QUALITY < 5 (dlq_2/ ulq_2) Network Doctor report 196 model


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Rx Quality x Rx Level

DL/UL QUALITY/LEVEL DISTRIBUTION Network Doctor report 204 model


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Rx Quality x Rx Level

Good Quality

HW Problem: Bad Quality for all Rx Levels

Coverage Problem: Bad quality and Low Rx Level

High Rv Level Interference Problem: Bad quality and High Rx Level NWD report 204 model


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Rx Quality x Rx Level •

Coverage Problem

• Bad Quality is due to weak signal. Check TA statistics. Add sites.

•

Interference Problem

• Internal interference. Check if interference profile follows increases in traffic profile. Check frequency plan and TA statistics. Modify frequency to verify if problem is solved. • External interference. Check if interference is independent of traffic profile. • Due to synchronisation problem. Synchronisation source set in BTS clock. Change to BSC.

•

HW Problem

• Bad quality in all RxLevel classes of ONE TRX. Check alarms to verify whether there is a badly functioning TRX. Fix hardware problem. Check antenna line. • Swap frequency. If problem persists on the same TRX, fix HW problem. • Bad quality in all RxLevel classes of TWO TRX. Verify combiner or common parts connected to both TRX.


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© 2006 Nokia


Timing Advance High share close: Most calls are established near the BTS BTS may have indoor coverage

Low share close: BTS might be so high that area bellow it does not receive any signal They might be another dominant site

High share far: May be causing Interference and drop call rate as traffic is captured in certain regions far from the BTS.


Don’t forget: 1. Traffic distribution depends on clutter types and planned coverage! 2. Repeters can change expected distribution. 177 08-11

© 2006 Nokia


Decreasing share: Traffic is distributed mostly in regions with higher signal level NWD report 232 model

Timing Advance • High share of traffic far from the BTS

• Internal Interference Problem: High drop call rate in a certain area. Rx Quality statistics indicates an internal interference problem. With planning tool evaluate sites with the same frequency - interfering candidates. TA statistics will show traffic distance of interfering cells. Downtilt is needed.

• No neighbours in area: High drop call rate. As this cell is covering na unexpected region, there will be no close neighbours declared and HO will not happen. Downtilt is needed. Soc Classification level 178 © Nokia Siemens Networks

178 08-11

© 2006 Nokia




ERLANG DROP PER MIN This KPI indicate the average time between the dropped calls. Its is a division of traffic expressed in minute –Erlangs divided by the total drops and is inversely proportional to DCR.



Congestion & blocking SDCCH congestion time (130,216) c2033 = sdcch_cong_time Bearer channel /NSVC (240) Circuit group blocking (602,604) M058, M026: Max. 1% in BH

Blocked SDCCH seiz att (216) c1001 = sdcch_busy_att Blocking (204,204, 130,216) , csf_1a RACH load rach_3, rach_4 (188, 216)

TCH congestion time (138, 216), c2027 = tch_cong_time Blocked TCH call att (216) blck_9c Blocking (204,200,138,216) , csf_3m,csf_3i,csf_3l 0026 SIGNALLING LINK LOAD OVER THRESHOLD (>0.2erl) 500627 AIV PAGING REFUSED BIG LOAD (BSCU overload )

RACH/NOISE COLLISION RACH

BTS TRX

MS

BSC

TC

Aif

Aif

MSC

Abis link Processor unit load (184,212) avg.70% critical avg.60% max. is recommended by R&D (avg. 50% for MB)

Paging Paging buffer occupancy pagings deleted (186)

SGSN

Signalling link (SS7) traffic (524) Add link if traffic > 200mErl

Access grant

Processor unit load (605,614) avg.70% critical (avg. 50% for MB)

No direct counter but affects csf_2j (200, 204, 250)

3164 PCU PROCESSOR OVERLOAD

HLR

AG blocking (229,204, 200, 216) (blck_13)

AG blocking, GPRS (229) (blck_21)

Alarm 2720 ‘Telecom Link overload’ (030) Alarm '7746' ‘Ch congestion in BTS above defined threshold' Soc Classification level 181 © Nokia Siemens Networks

NOTE: In MSC terminology instead of term ‘blocking’ there is term ‘call congestion'

Processor unit load (606,615) avg.70% critical (avg. 50% for MB)

NOTE:The lines indicate logical source of the info, the actual genereation of the info can be in the above standing object

ALARM ANALYSIS Alarm Number

Description

7745

CHANNEL FAILURE RATE ALARM

2992

BtTS and Tc unsynchronization clear calls on a interface

2993

BTS andTC unsynchronization clear calls on abis interface

7508

RADIO TIMESLOT FAILURE IN TRX

7600

BCF FAULTY

7601

BCF OPERATION DEGRADED

7603

BTS FAULTY

7604

BTS Operation Degraded

7606

TRX FAULTY

7617

SEVERAL CALLS DROPPED DUE TO PROBLEM WITH TRANSCODER

7704

PCM FAILURE

7705

LAPD FAILURE

7715

CONTINUOUS RESTARTS OF BCF-TRX

7725

TRAFFIC CHANNEL ACTIVATION FAILURE

7738

BTS WITH NO TRANSACTIONS

7743

MEAN HOLDING TIME BELOW DEFINED THRESHOLD

2955

TRANSCODER CHANNEL FAILURE

7746

CH CONGESTION IN CELL ABOVE DEFINED THRESHOLD

7767

BCCH MISSING

7939

FORWARD POWER TOO LOW AT TX ANTENNA

8112

FREQUENCY ERROR



7755—Channel failure rate above defined Threshold



7745



7745



7745



7601-BCF OPERATION DEGRADED BCF Operation Degraded

BD018

BCF-0030

EQUIPM

:This alarm 7601 is generated at the BTS.

2007-07-24 04:20:45.42

** ALARM (14652) 7601 BCF OPERATION DEGRADED Difference between PCM and base station frequency reference. 02 01 07 96 00 00 1) Fault reason: Cabinet I2C bus is jammed. Solution: 1)Switch the site power Off and On. 2)Check the fan unit, the power supply unit and the TRXs. If necessary, replace the faulty units(s). 3)If the fault reappears, replace the cabinet. The units inside the cabinet can be reused in the new cabinet 2) Fault reason: Incompatible unit presence has been detected in the BTS. Solution: •Replace the high power or EDGE TRX(s) with normal type TRX(s) and reset the BCF •Or, replace the normal type FAN and power supply with high power or EDGE units. Now EDGE and high power TRXs are supported. Soc Classification level 187 © Nokia Siemens Networks


7601 3) Fault reason: Difference between the PCM and BTS frequency reference.

Solution: •Check the synchronisation settings of the transmission interface.( DAC Value)DAC value Range from 1800 t0 2200. •If the settings are OK, check the transmission chain. •If the alarm stays active or reappears after the recovery actions above, reset the BCF. •If the alarm reappears after the BCF reset, replace the BTS. Note: If this Supplementary alarm appears there is Drift in clock value(DAC). That leads to HO failures 4) Fault reason: Oven oscillator control is close to its margins. The oven might be outdated. Solution: •Check the synchronisation settings of the transmission interface. •If the settings are OK, check the transmission chain. •If the alarm stays active or reappears after the recovery actions above, reset the BCF. •If the alarm reappears after the BCF reset, replace the BTS Note: If this Supplementary alarm appears there is Drift in clock value (DAC). That leads to HO failures 5) Fault reason: Flash operation failed in BOI or TRX. Solution: Replace the BOI (Base station operation Interface unit) If it is TRX change the TRX Descrpition of Supplementary information: 1-6 XX XX XX XX XX XX 1 2 3 4 5 6 1 Rack (cabinet) number 2 shelf number 3 slot 4 Type of unit 5 unit number 6 subunit number Soc Classification level 188 © Nokia Siemens Networks



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