AIRCOM Asset LTE Basics and Asset

Section 1: LTE Air-Interface Instructor – Ishan Marwah 1

© 2012 AIRCOM International Ltd

Roadmap 2G

2.5G

3G phase 1

Evolved 3G

LTE HSUPA* HSDPA WCDMA EDGE GPRS GSM

2000/2001 2

2003/2004

2005

2007

2010


Where are we?

 LTE is now on the market (both radio and core network evolution)  Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment

 Enhancements to LTE were frozen in to release 9 in December 2009 3


Flat Architecture Traditional Architecture GGSN

One Tunnel Architecture REL7

LTE

GGSN

SAE GW

SAE /GW– System Architecture Evolution

IP Network

SGSN

SGSN IP Network

RNC

RNC

MME

MME - Mobility Management Entity

IP Network

NODE B

NODE B

eNODEB

eNodeB - evolved Node B

Control plane User plane 4


LTE Network Architecture Evolved UTRAN (E-UTRAN)

Evolved Packet Core (EPC) HSS

MME: Mobility Management Entity

S6a

Evolved Node B (eNB)

MME

X2

S1-MME

PCRF

S5

S1-U

5

Policy & Charging Rule Function

S11

LTE-UE

LTE-Uu

S7

IMS Serving Gateway

PDN Gateway


Release 8– LTE – New Air interface The LTE DOWNLINK uses OFDMA

   

Orthogonal Frequency Division Multiple Access This new OFDMA based air interface is also often referred to as the Evolved UMTS Terrestrial Radio Access Network (EUTRAN) 300 Mbit/s per 20 MHz of spectrum

Uplink

 uses Single Carrier Frequency Division Multiple Access (SC-FDMA)  Single Carrier Frequency means information is modulated only to one carrier, adjusting the phase or amplitude of the carrier or both

 75 Mbit/s per 20 MHz of spectrum OFDMA

eNODE B

SC-FDMA 6


The Physical Layer - OFDM and OFDMA

Orthogonal Frequency Division Multiplexing

Orthogonal Frequency Division Multiple Access

7

Each user is assigned a specific frequency resource

Each user is assigned a specific timefrequency resource © 2012 AIRCOM International Ltd

Multiple Access DL LTE employs OFDM as the basic modulation scheme and multiple access is achieved through: •

OFDMA in the LTE Downlink • A multi-carrier signal with one data symbol per subcarrier • Scalable to wider bandwidths, multipath resilient and better suited for MIMO architecture • Drawback: Parallel transmission of multiple symbols creates undesirable high PAPR

8


Multiple Access UL SC-OFDMA in the LTE Uplink • SC-FDMA transmits the four QPSK data symbols from a user in series at four times the rate, with each data symbol occupying N x 15 kHz bandwidth. • Signal more like single carrier with each data symbol being represented by one wide symbol • Occupied bandwidth same as OFDMA but crucially, the PAPR is the same as that used for original data symbol

9


Advanced Antenna Techniques

Use multiple channels to send multiple information streams (spatial multiplexing) • Increase throughput

MIMO creates multiple parallel channels between transmitter and receiver. MIMO is using time and space to transmit data (space time coding).

• MIMO needs a high signal-to-noise ratio (SNR) at the UE • High SNR ensures that the UE is able to decode the incoming signal • This ensures good orthogonality 10


LTE - FDD/TDD FDD

TDD

F -DL F -UL

There are two types of LTE frame structure:

 Type 1: used for the LTE FDD mode systems.  Type 2: used for the LTE TDD systems.  LTE can be used in both paired (FDD) and unpaired (TDD)  11

spectrum. FDD & TDD supports bandwidths from 1.4 Mhz to 20Mhz


FDD  Type 1 used for the LTE FDD mode systems.  The basic type 1 LTE frame has an overall length of 10

ms. This is then divided into a total of 20 individual slots. LTE Subframes then consist of two slots - in other words there are ten LTE subframes within a frame. 10 ms

0

1

2

3

19

One Subframe = 1 mS 12


TDD Type 2 LTE Frame Structure

 The frame structure for the type 2 frames used on LTE TDD is

somewhat different. The 10 ms frame comprises two half frames, each 5 ms long. The LTE half-frames are further split into five subframes, each 1ms long.

10 ms

0

13

2

3

4

0

1

2

3

4


TDD One radio frame Tf =10 ms

One half- frame Thf = 5 ms

special sub-fames

Sub-frame #0

Sub-frame #2

DwPTS

Sub-frame #3

Sub-frame #4

UpPTS

Sub-frame #5

Sub-frame #7

DwPTS

GP

Sub-frame #8

Sub-frame #9

UpPTS GP

The special subframes consist of the three fields:

 DwPTS (Downlink Pilot Timeslot)  GP (Guard Period)  UpPTS (Uplink Pilot Timeslot) 14


TDD  A total of seven up / downlink

configurations have been set, and these use either 5 ms or 10 ms switch periodicities.

 “S” denotes the special subframe when you go from DL to U

 The special subframes consist of the three fields: DwPTS (Downlink Pilot Timeslot), GP (Guard Period), and UpPTS (Uplink Pilot Timeslot)

15

0

1

2

3

19 10 ms


Flexible Carrier Bandwidths  LTE is defined to

support flexible carrier bandwidths from 1.4MHz up to 20MHz, in many spectrum bands and for both FDD and TDD deployments

 Supported LTE modes of operation:

 Frequency Division Duplex (FDD)  Time Division Duplex (TDD) 16


E-UTRA Bands and Channel Bandwidths  E-UTRA bands are regulated to allow

operations in only certain set of Channel Bandwidths which are defined as

 The RF bandwidth supporting a

single E-UTRA RF carrier with the transmission bandwidth configured in the uplink or downlink of a cell

 Channel bandwidth is measured in MHz

and is used as a reference for transmitter and receiver RF requirements

 Some EUTRA bands do not allow

operation in the narrow bandwidth modes , i.e. < 5 MHz

 Others restrict operations in the wider channel bandwidths, i.e. > 15 MHz

17

Supported Channels (non-overlapping) E-UTRA Band

Downlink Bandwidth

Channel Bandwidth (MHZ)

1.4 3 5 1 60 12 2 60 42 20 12 3 75 53 23 15 4 45 32 15 9 5 25 17 8 5 6 10 2 7 70 14 25 7 8 35 11 9 35 7 10 60 12 11 25 5 12 18 12 6 3* 13 10 7 3 2* 14 10 7 3 2* ... 33 20 4 34 15 3 35 60 42 20 12 36 60 42 20 12 37 20 4 38 50 10 39 40 8 40 100 * UE receiver sensitivity can be relaxed X Channel bandwidth too wide for the band Not supported

10 6 6 7 4 2* 1* 7 3* 3 6 2* 1* 1* 1*

15 4 4* 5* 3 X 4 2* 4 1* X X

20 3 3* 3* 2 X 3* 1* 3 1* X X X

2 1 6 6 2 5 4 10

1 1 4 4 1 3 6

1 X 3 3 1 2 5


LTE Bands

18


Comparison FDD/TDD 1. FDD LTE uses frequency division, while TDD LTE uses time division

2. FDD LTE is full duplex, while TDD LTE is half duplex 3. FDD LTE is better for symmetric traffic, while TDD is better for asymmetric traffic

4. FDD LTE allows for easier planning than TDD LTE FDD base stations use different frequencies for receiving and transmitting, they effectively do not hear each other and no special planning is needed. With TDD, special considerations need to be taken in order to prevent neighbouring base stations from interfering with each other

19


Sub-Carriers

GSM

15Khz Spacing saving bandwidth. 12 carriers for 0.5ms LTE

200Khz QPSK b0 b 1 Im

01

11

00

10Re

16QAM b0 b1b2b3 Im 1111

Re

64QAM b0 b1b2b3 b4 b5 Im

Re

7.5Khz Spacing saving bandwidth. 24 subcarriers for 0.5 ms.

0000 20


Slot Structure and Physical Resources  ONE slot = 12 consecutive subcarriers

 One slot = 0.5mS  6 or 7 OFDM symbols

(depending upon cyclic perfix size), thus a single resource block is containing either 72 or 84 OFDM symbols

 12x 7 = 84 OFDM symbols

21


Slot Structure and Physical Resources One Slot = 0.5mS QPSK b0 b1 Im

16QAM b0 b1b2b3 Im 1111

01

11

00

10Re

Re 0000

64QAM b0 b1b2b3 b4 b5 Im

Re

22


Channel BW CHANNEL BW (Mhz)

Nrb

BW config= % of Nrb x 12 x15 Channel 1000 BW

1.4

6

1.08

77%

3

15

2.7

90%

5

25

4.5

90%

10

50

9

90%

15

75

13.5

90%

20

100

18.0

90%

BW Channel BW config R R R R R R R R R R R R R B B B B B B B B B B B B B 23


Slot Structure and Physical Resources

24

Bandwidth (MHz)

1.4

3

5

10

15

20

# of RBs

6

15

25

50

75

100

Subcarriers

72

180

300

600

900

1200


Cyclic Prefix  In the time domain, a guard interval may be added to each symbol to combat inter-OFDM-symbol-interference due to channel delay spread

 The guard interval is a cyclic prefix which is inserted prior to each OFDM symbol cyclic prefix One sub Frame=1mS One Slot = 0.5ms

7 OFDM Symbols

7 OFDM Symbols All Data

The length of the cyclic prefix, CP is important. If it is not long enough then it will not counteract the multipath reflection delay spread. If it is too long, then it will reduce the data throughput capacity. 25


Delay Spread Normal

2

1 3 Time Domain

For LTE, the standard length of the cyclic prefix has been chosen to be 4.69 µs.

Direct signal Reflection 1

Last Reflection

Guard Period 26

This enables the system to accommodate path variations of up to 1.4 km. With the symbol length in LTE set to 66.7 µs

Sampling Window


Cyclic Prefix  To each OFDM symbol, a cyclic prefix (CP) is appended as guard time  One downlink slot consists of 6 or 7 OFDM symbols, depending on whether extended or normal cyclic prefix is configured, respectively

 The extended cyclic prefix is able to cover larger cell sizes with higher delay spread of the radio channel

27


Slot Structure and Physical Resources Each 1ms Transmission Time Interval (TTI) consists of two slots (Tslot)

28


OFDMA and Throughputs To symbol rate of 1/15KHz = 66.7us Therefore 15 Kilosymbols per second

For 20Mhz bandwidth (1200 carriers) symbol rate = 1200 x 15= 18Msps

15kHz

66.7us

Each symbol using 64 QAM (6 bits) Total peak rate = 18 Msps x 6 bits = 108Mbps Subtract overhead and coding and add gains (MIMO) Each symbol 2 bits(QPSK), 4 Bits (16 QAM) and 6 bits 64 QAM

29


Downlink Reference Signal Structure RSRP is applicable in both RRC_idle and RRC_connected modes

Downlink reference signal PDSCH

Downlink reference signal structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 1 antenna. Ref Signal TX1= 8 for 15Khz spacing

RSRP (Reference Signal Received Power)

RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth. 30


Configuration of Carrier  Note that when multiple antennas are used for transmission, then there is a resource grid for each one.

 EUTRAN support 1, 2 or 4 antennas, called the antenna ports

R0

R0 R0 R0

R0 R0

R0

R0

Port 3

R0 R0

Port 2

R0

R0

R0 R0

R0

R0 R0

R0 R0

R0

Port 1

R0 R0

R0

R0 R0

R0

R0 R0

R0 R0

31

Port 4

R0

R0


Configuration of Carrier - 1 Antenna Carrier 1 Overhead

R0

R0

R0

R0

R0

R0

R0

R0

Specific pre-defined resource elements (indicated by R0-3 in in the time-frequency domain are carrying the cell-specific reference signal sequence. 32

REF, Control, Broadcast, Syn

Downlink Reference Signal Structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 1 antenna. Ref Signal TX1 = 8 for 15Khz spacing


Configuration of Carrier - 2 Antenna Carrier 1

Overhead

R1

R0

R0

R1

R1

R1

R0

R1

R1 R0

R0

R0

R1

R0

R0

R1



Downlink Reference Signal Structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 2 antenna. Ref Signal TX2= 16 for 15Khz spacing © 2012 AIRCOM International Ltd

Configuration of Carrier - 3 Antenna Carrier 1

Overhead


Downlink Reference Signal Structure R1

R0

R0

R2

R1

R1

R1 R2

R0

R1

R1 R2 R0

R0 R2

R0

R1

R0

R0

R1


The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 2 antenna. Ref Signal TX3= 20 for 15Khz spacing


Configuration of Carrier - 4 Antenna Carrier 1 Overhead

R1

R0

R3

R2

R0

R1

R1 R3

R1 R2

R0 R3

R1

R1 R2 R0

R0 R2

R0

R1

Downlink reference signal structure The downlink reference signal structure is important for channel estimation.

R0

R0 R3

R1



The principle of the downlink reference signal structure for 2 antenna. Ref Signal TX3= 20 for 15Khz spacing


Type1-DL Frame

36


FDD Frame Structures UL Type1-FDD- Uplink UL Control Channel • PUCCH transmission in one subframe is compromised of single PRB at or near one edge of the system bandwidth followed by a second PRB at or near the opposite edge of the bandwidth • PUCCH regions depends on the system bandwidth. Typical values are 1, 2, 4, 8 and 16 for 1.4, 3, 5, 10 and 20 MHz UL Signals(S-RS & DM RS) • S-RS estimates the channel quality required for the UL frequency-selective scheduling and transmitted on 1 symbol in each subframe • DM-RS is associated with the transmission of UL data on the PUSCH and\or control signalling on the PUCCH • mainly used for channel estimation for coherent demodulation • transmitted on 2 symbols in each subframe 37


Type1- UL Frame

38


RSRQ (Reference Signal Received Quality)  In LTE network, a UE measures:  RSRQ (Reference Signal Received Quality) RSRQ is defined as the ratio N×RSRP / (E-UTRA carrier RSSI)

LTE_ACTIVE state RSRP is applicable RRC connected modes 39


Frequency Band Considerations  Fifteen FDD band options and eight TDD band  The specific spectrum availability will depend on the country and region in which the network will operate.

 An operator may already have licensed spectrum available in which LTE

could be rolled out. This may be because an older legacy technology can be progressively switched off, or because they have spectrum that is currently unused

 Given the possible expense of purchasing new radio licences, most

operators will at least consider the possibility of refarming their existing licensed spectrum for LTE use.

 In most cases, however, an operator will need to consider purchasing new spectrum in which to operate LTE. Even when new spectrum is available, an operator will need to consider a number of configuration options.

40


Propagation (Path Loss) Models A propagation model describes the average signal propagation, and it converts the maximum allowed propagation loss to the maximum cell range. It depends on:

• Environment : urban, rural, dense urban, suburban, open, forest, sea…

• Frequency • atmospheric conditions • Indoor/outdoor 41


Free Space Path Loss  For typical radio applications, it is common to find measured in

units of MHz and in km, in which case the FSPL equation becomes:

FSPL= 32.5 + 20 log10(d) + 20 log10(f)

dBm

 Free-Space Path Loss (FSPL) is the loss in signal strength of an

electromagnetic wave that would result from a line-of-site path through free space, with no obstacles nearby to cause reflection or diffraction.

42


Free Space Path Loss Formula at 1800Mhz  Lo = 32.5 + 20 log(d) + 20 log(fMhz) dBm What is the free space path loss at: 1800Mhz at 1Km

What is the free space path loss at: 1800Mhz at 10Km


20 log (1) + 20logx1800

20 log (10) + 20log1800

20 log (100) + 20log10x1800

=0 +65

=20 +65

=40 +65

=32.5 + 65 dB

=32.5+85dB

=32.5+105dB

=97.5

=117.5

=137

20dB different 43


Free Space Path Loss Formula at 900Mhz:  Lo = 32.5 + 20 log10(d) + 20 log10(fMhz) dBm What is the free space path loss at: 900Mhz at 1Km



20 log (1) + 20log x 900

20 log (10) + 20log x 900

20 log (100) + 20log10x900

=0 + 59

=20 +59

=40 +59

=32.5 + 59dB

=32.5+79dB

=32.5+99dB

=91.5dB

=111.5dB

=131.5

20dB different 44


Examples What is the free space path loss at: 1800Mhz at 1Km

1800Mhz at 10Km


20 log (1) + 20logx1800

20 log (10) + 20log1800

20 log (100) + 20log10x1800

=0 +65

=20 +65

=40 +65

=32.5 + 65 dB

=32.5+85dB

=32.5+105dB

=97.5

=117.5

=137

What is the free space path loss at:



45


900Mhz at 10Km

900Mhz at 100Km

20 log (1) + 20log x 900

20 log (10) + 20log x 900

20 log (100) + 20log10x900

=0 + 59

=20 +59

=40 +59

=32.5 + 59dB

=32.5+79dB

=32.5+99dB

=91.5dB

=111.5dB

=131.5


Frequency Band Considerations  The frequency ranges covered by the

defined operating bands for LTE vary greatly and include bands based around 700 MHz up to bands around 2.6 GHz.

 The band makes a significant difference to the number of sites required for network rollout.

 11.4 dB difference in free space path loss between 700 MHz and 2.6 GHz.

700 MHz

2.6 GHz 46

At 700 MHz could be between three and four times larger than at 2.6 GHz. © 2012 AIRCOM International Ltd

Frequency Band Considerations 700 MHz • In the U.S. this commercial spectrum is scheduled to be auctioned in January 2008

• This includes 62 MHz of spectrum broken into 4 blocks: • • • • •

A (12 MHz) B (12 MHz) E (6 MHz unpaired) C (22 MHz) D (10 MHz)

• These bands are highly prized chunks of spectrum and a tremendous

resource: the low frequency is efficient and will allow for a network that doesn’t require a dense build out and provides better in-building penetration than higher frequency bands.

47


Frequency Band Considerations Refarming GSM 900 MHz

 900MHz offers improved building penetration and is particularly well suited to supporting those regions that have a predominantly rural population.

 The ongoing subscriber migration from GSM to UMTS taking place in over 150 countries worldwide is relieving pressure on the GSM900 networks and is starting to free up some spectrum capacity in that band.

 Deploying LTE in 900MHz can also bring the additional cost and logistic

benefits of being able to deploy LTE at existing GSM sites as the coverage of GSM/LTE in 900MHz should be very similar.

 Compared to HSDPA/HSDPA+, LTE is expected to substantially improve enduser throughputs, sector capacity and reduce user plane latency to deliver a significantly improved user experience. As such, the industry expects that Service Providers will wait to deploy LTE in the refarmed 900 MHz

48


Frequency Band Considerations Frequency Planning

 How much spectrum an operator may have access to. Historically, radio licences for 20 MHz,either TDD or FDD, have been rare.

 Much more common would be 10–15 MHz. Additionally, it must be borne in mind that in most implementations some form of frequency plan must be used.

 For example, an operator with a licence for 15 MHz may need to implement this as three 5 MHz channels.

 It is possible to implement LTE as an SFN (Single Frequency Network), but the high level of interference at cell edges reduces the available bandwidth unless Interference Management Systems are used.

49


Questions

50


Questions 1. What is the maximum bit rate if you assign a

bandwidth of 10Mhz to a sector and a UE is allocated all RB?

51




52




53


Questions 4. What is meant by Normal type1?

5. Compare band 13 to band 1?

6. What is meant by GSM re-farming?

54


Session 02 Setting up a LTE Network in Asset

55


Antenna Database Antenna Information and Mask

56


Setting up a Propagation Model Propagation models are mathematical attempts to model the real radio environment as closely as possible. Most propagation models need to be tuned (calibrated) by being compared to measured propagation data, otherwise you will not be able to obtain accurate coverage predictions.

57


Std. Macrocell Propagation Model  Asset Standard Macrocell model

PL K1 K 2log (d ) K 3H ms

K 4logH ms

K 5logH eff

K 6log ( H eff )log (d ) K 7(diffraction loss) Clutter loss

58


Recommended Starting Parameters

59

K values

450 MHz

900 MHz

1800 MHz

2000 MHz

2500 MHz

3500 MHz

k1 for LOS

142.3

150.6

160.9

162.5

164.1

167

k2 for LOS

44.9

44.9

44.9

44.9

44.9

44.9

k1 (near) for LOS k2 (near) for LOS d < for LOS

129.00

0.00

0.00

0.00

0.00

0.00

31.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

k1 for NLOS

142.3

150.6

160.9

162.5

164.1

167

k2 for NLOS

44.9

44.9

44.9

44.9

44.9

44.9

k1 (near) for NLOS k2 (near) for NLOS d < for NLOS

129.00

0.00

0.00

0.00

0.00

0.00

31.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

k3

-2.22

-2.55

-2.88

-2.93

-3.04

-3.20

k4

-0.8

0.00

0.00

0.00

0.00

0.00

k5

-11.70

-13.82

-13.82

-13.82

-13.82

-13.82

k6

-4.30

-6.55

-6.55

-6.55

-6.55

-6.55

k7

0.4

0.7

0.8

0.8

0.8

0.8 © 2012 AIRCOM International Ltd

MME and SAE-GW Support Asset support for hieratically higher LTE network elements

 Mobility Management Entity (MME)  System Architecture Evolution Gate Way (SAE-GW)  Support for Logical/Cellular Connections that allow

for the mesh-type parent-child relationships of the LTE Core.  eNodeB can be parented to both an SAEGW and

MME and can be parented to multiple SAEGWs and/or MMEs

60


MME and SAE-GW Support

61


LTE Frame Structures

62


LTE Frequency Bands

63


LTE Carriers

64


LTE Carriers

65


Interference Co-ordination Schemes To minimize Intercell Interference following frequency reuse schemes are being considered Frequency Reuse-1 with Prioritization • Each sector divides the available bandwidth into prioritized (one third) and nonprioritized (two third) sections disregard of CE or CC. • Prioritized spectrum is used more often than non-prioritized by each sector in order to concentrate the interference that it causes to other sectors

66


Interference Co-ordination Schemes Soft Frequency Reuse • Power difference between the prioritized and non-prioritized spectrum which divides the sector into an inner and an outer region • User in the inner region can be reached with reduced power, i.e. Cell Centre Users (CCU) than the users in the outer region i.e. Cell Edge Users (CEU) • CCU are assigned frequency Reuse-1 while CEU employ Reuse-3 with soft reuse

67


Interference Coordination Schemes Reuse Partitioning • Similar to Soft Frequency Reuse • High-power part is divided between sectors so that each sector gets one third of the highpower spectrum • Low-power part employs frequency Reuse-1 while high-power part is configured with a frequency Reuse-3 with hard reuse.

68


Interference Coordination Schemes

69


MIMO - Transmit Diversity Instead of increasing data rate or capacity, MIMO can be used to exploit diversity and increase the robustness of data transmission. Each transmit antenna transmits essentially the same stream of data, so the receiver gets replicas of the same signal.

010100

010100

T X

R X

SU-MIMO

010100

70


MIMO - Spatial Multiplexing Spatial multiplexing allows an increase in the peak rates by a factor of 2 or 4, depending on the eNodeB and the UE antenna configuration. Spatial multiplexing allows to transmit different streams of data, different reference symbols simultaneously on the same resource blocks

010

010100

T X

R X

SU-MIMO

100

71


LTE Downlink Transmission Modes • LTE Rel 8 supports DLtransmission on 1, 2, or 4 antenna ports: •

1, 2, or 4 cell-specific reference signals

• each reference signal corresponds to one antenna port

• DL transmission modes are defined for PDSCH (Data\Traffic) • Single antenna (No MIMO)

• Transmit diversity • Open loop Spatial multiplexing

SU-MIMO

• Closed loop spatial multiplexing • Multi user MIMO

• Closed-loop precoding for Rank=1 (No spatial Mux, But precode) • Conventional beamforming • UL MIMO Modes • Transmit diversity

• Receive Diversity • MU-MIMO 72


SU-MIMO • This includes conventional techniques such as • Cyclic Delay Diversity • Transmit\Receive diversity (Space frequency block codes)

• Spatial Multiplexing\ Precoded Spatial Multiplexing • Can be implemented as Open and Closed loop • Diversity techniques improves the signal to interference ratio by transmitting same stream of single user data. • Spatial multiplexing increases the per user data rate\throughput by transmitting multiple streams of data dedicated for a single user

73


MU-MIMO • Multiple users (separated in the spatial domain in both UL and DL) sharing the same time-frequency resources • Uses multiple narrow beams to separate users in the spatial domain and can be considered as a hybrid of beamforming and spatial multiplexing. • Serves more terminals by scheduling multiple terminals using the same resources • this increases the cell capacity and number of served terminals • Suitable for highly loaded cells and for scenarios where number of served terminals is more important than peak user data rates

74


Lookup Table for AAS

75


Templates for Sites When planning a network, Instead of setting the parameter values on each node individually, you can define templates, then select one of these templates as a basis for adding new nodes. The new nodes will then contain the default characteristics of the template.

76


Adding Sites/Cells  You can add network elements by using the site

design toolbar in the Map View window and also by using the Site Database window.

 You need the correct privileges to be able to add

and modify network elements. Contact your administrator if you do not have the correct permissions

77


AAS Settings in Site DB

78


LTE Parameters

79


Scheduler Scheduler Round Robin

Proportional Fair

Proportional Demand

Max SINR

80

Description The aim of this Scheduler is to share the available/unused resources equally among the terminals (that are requesting RT services) in order to satisfy their RT-MBR demand. This is a recursive algorithm and continues to share resources equally among terminals, until all RTMBR demands have been met or there are no more resources left to allocate. The aim of this Scheduler is to allocate the available/unused resources as fairly as possible in such a way that, on average, each terminal gets the highest possible throughput achievable under the channel conditions. This is a recursive algorithm. The available/unused resources are shared between the RT terminals in proportion to the bearer data rates of the terminals. Terminals with higher data rates get a larger share of the available resources. Each terminal gets either the resources it needs to satisfy its RTMBR demand, or its weighted portion of the available/unused resources, whichever is smaller. This recursive allocation process continues until all RT-MBR demands have been met or there are no more resources left to allocate. The aim of this Scheduler is to allocate the available/unused resources in proportion to the RT-MBR demand, which means that terminals with higher RT-MBR demand achieve higher throughputs than terminals with lower RT-MBR demand. This is a non-recursive resource allocation process and results in either satisfying the RT-MBR demands of all terminals or the consumption of all of the available/unused resources. The aim of this Scheduler is to maximise the terminal throughput and in turn the average cell throughput. This is a non-recursive resource allocation process where terminals with higher bearer rates (and consequently higher SINR) are preferred over terminals with low bearer rates (and consequently lower SINR). This means that resources are allocated first to those terminals with better SINR/channel conditions than others, thereby maximising the throughput. © 2012 AIRCOM International Ltd

LTE Parameters

81

Load (%)

Interference Margin (dB)

35

1

40

1.3

50

1.8

60

2.4

70

2.9

80

3.3

90

3.7

100

4.2


Session 03 Predicting and Displaying Coverage

82


Predicting Coverage

83


Best RSRP Coverage Example

84


Array Display Properties To customise the arrays displayed in the Map View window, Use the Show Data Types button.

85


Coverage Reports/Statistics Once coverage arrays have been created, you can generate coverage statistics.

86


Coverage Reports/Statistics

87


Array Manager Array manager enable memory management on arrays and simulations. In addition, the Array Manager provides the ability to retrieve archived arrays, allowing for the benchmarking of statistical changes over time.

88


Session 04 Traffic Planning on a LTE Network

89


Default LTE Bearers Bearers represent the air interface connections, performing the task of transporting voice and data information between cells and terminal types.

90


Channel Quality Indicator Tables Indicates a combination of modulation and coding scheme that the NodeB should use to ensure that the BLER experienced by the UE remains < 10%

64 QAM 16 QAM QPSK

UE4 eNB UE5

UE2 UE1

91

UE3

CQI

Modulation

Efficiency

Actual coding rate

Required SINR

1

QPSK

0.1523

0.07618

-4.46

2

QPSK

0.2344

0.11719

-3.75

3

QPSK

0.3770

0.18848

-2.55

4

QPSK

0.6016

308/1024

-1.15

5

QPSK

0.8770

449/1024

1.75

6

QPSK

1.1758

602/1024

3.65

7

16QAM

1.4766

378/1024

5.2

8

16QAM

1.9141

490/1024

6.1

9

16QAM

2.4063

616/1024

7.55

10

64QAM

2.7305

466/1024

10.85

11

64QAM

3.3223

567/1024

11.55

12

64QAM

3.9023

666/1024

12.75

13

64QAM

4.5234

772/1024

14.55

14

64QAM

5.1152

873/1024

18.15

15

64QAM

5.5547

948/1024

19.25


LTE Services The parameters that you specify will influence how the simulation behaves and will enable you to examine coverage and service quality for individual types of service.

92


LTE Services and QoS Parameters

93

Name

QCI

VoIP Video Call

Priorit y

1 2

Resourc e Type GBR GBR

2 4

Packet Delay Budget 100 ms 150 ms

Packet Error Loss Rate 10-2 10-3

Gaming Streaming

3 4

GBR GBR

3 5

50 ms 300 ms

10-3 10-6

Signalling E-mail Web browsing P2P File Sharing Chat

5 6 7

Non-GBR Non-GBR Non-GBR

1 6 6

100 ms 300 ms 100 ms

10-6 10-6 10-3

8

Non-GBR

8

300 ms

10-6

9

Non-GBR

9

300 ms

10-6

Example Services Conversational Voice Conversational Video (Live Streaming) Real Time Gaming Non-Convers.Video (Buff. Streaming) IMS Signalling Video (Buffered Streaming), TCP-based (www, e-mail, chat, ftp, p2p sharing, Progressive video, etc.) Voice, Video (Live Streaming) Interactive Gaming


Clutter Parameters You can define different shadow fading standard deviations for outdoor terminals and indoor terminals per clutter type. If a building is in urban, it will encounter greater fading than in parkland. You can also specify different indoor losses for each clutter type.

94


Terminal Types ASSET models traffic demand by generating traffic density maps for the different types of terminal. These density maps define the amount of traffic offered to the network by each type of terminal on a pixel-bypixel basis, corresponding to the available clutter map data resolutions. A Terminal Type in ASSET defines these key characteristics:

 How much ‘traffic’ will the terminal type generate in total?  How will the ‘traffic’ be spread geographically?  What is the expected mobile speed distribution for this terminal type?

 Which service will the terminal type provide?*  What are the mobile equipment characteristics?

95


LTE Terminal Types

96


LTE User Equipment Categories

97

Parameters

Category 1

Category 2

Category 3

Category 4

Category 5

Peak Data Rate (DL)

10 Mbps

50 Mbps

100 Mbps

150 Mbps

300 Mbps

Peak Data Rate (UL) Block Size (DL) Block Size (UL)

5 Mbps 10296 5160

25 Mbps 51024 25456

50 Mbps 102048 51024

50 Mbps 149776 51024

75 Mbps 299552 75376

Max. Modulation (DL) Max. Modulation (UL) RF Bandwidth Transmit Diversity Receive Diversity Spatial Multiplexing (DL) Spatial Multiplexing (UL) MU-MIMO (DL) MU-MIMO (UL)

64QAM 16QAM 20 MHz 1-4 Tx Yes Optional No Optional Optional

64QAM 16QAM 20 MHz 1-4 Tx Yes 2X2 No Optional Optional





Traffic Rasters Traffic Rasters are arrays that store the distribution of traffic over an area. They can be created either from the information in the Terminal Types or from imported Live Traffic values. The name of the created traffic raster will be the same as the name of the terminal type. The Traffic Rasters enables you to:

 Obtain initial estimates of the equipment and configuration needed

for a nominal network. By visualising the array, you can then gain a good idea of where to locate your sites.

 Can assess how your network performs in terms of capacity for a

mature network. Can verify site configuration is sufficient to match the traffic spread over the network.

98


Creating Traffic Rasters

99


Traffic Rasters

100


Session 5 Simulating Network Performance

101


LTE Simulator Wizard

102


Simulation without Snapshots If you run a simulation without running snapshots (static analysis) you must ensure that the cell loading parameters for the cells/sectors have been specified in the Site Database. The parameters are set on the Cell Load Levels subtab under LTE Params tab.

103


Simulator Outputs ASSET provides ways of setting your own array definitions, so that you can specify exactly which arrays you want to be output when you use the Simulator. The easiest way is to use the Auto Setup option. This ensures that all the relevant array types and their parameter combinations are included in the simulation outputs for display and analysis.

You can also define your own customised collection of output array types from the Simulator. This enables you to specify array definitions to determine precisely which arrays you want to output and display, in any combination of parameters you choose. This method is probably only beneficial for advanced users.

104


Simulation – Best RSRP

105


Street Coverage prediction analysis using the Vector Restriction feature Best RSRP is calculated for whole 2D View

106

Best RSRP is calculated to streets only


Simulation – RSRQ

107


Simulation – Cell Centre / Cell Edge

108


Simulation – Achievable DL Bearer

109


Simulation – DL RS SINR

110


Simulation – DL Transmission Mode

111


Information about Simulated Terminals  The aim of this feature is to provide the user with a set of

arrays that show the locations of terminals generated by the simulation snapshots, and to show whether the terminals succeeded or failed to make a connection. The following arrays are provided for each terminal type used in the simulation.

•

Terminal Info: Failure Rate

•

Terminal Info: Failure Reason

•

Terminal Info: Speed

 The arrays are only available in simulations that run snapshots,

and where the user has checked the Allow Terminal Info Arrays box on the 2nd page of the simulation wizard.

112


Information about Simulated Terminals Failure Reason array. 1 snapshot

Failure Reason array. 500 snapshots

113


Line-of-Sight array and improved MIMO Modelling

114



AIRCOM Enhanced Macrocell model (as well as some 3rd party prediction models – complete list TBD) have the ability to produce line-of-sight (LOS) information for each predicted location, in addition to the existing pathloss value.



Using LOS info in a simulation can be used to improve MIMO modelling.



MIMO schemes rely on there being a low correlation between the signal paths to the receive elements of an antenna. Locations that have line-of-sight to an antenna are more likely to have high correlation between signal paths to the antenna.



The LTE simulator supports 3 basic MIMO schemes: SU-MIMO Multiplexing, SU-MIMO Diversity, and MU-MIMO. A new page is added to the LTE simulation wizard, providing the user with the option of enabling/disabling these 3 MIMO schemes in LOS regions.



If a prediction model is used that does not generate LOS info, then the sim will treat pathlosses from that model as non-LOS. © 2012 AIRCOM International Ltd

Line-of-Sight array and improved MIMO Modelling

115


Pixel Analyser The Pixel Analyser visualises detailed signal strength information that has been accumulated during a simulation.

116


Session 6 LTE Architecture

117


Flat Architecture Traditional Architecture GGSN

One Tunnel Architecture REL7

LTE

GGSN

SAE GW

SAE /GW– System Architecture Evolution

IP Network

SGSN

SGSN IP Network

RNC

RNC

MME

MME - Mobility Management Entity

IP Network

NODE B

NODE B

eNODEB

eNodeB - evolved Node B

Control plane User plane 118


LTE Network Architecture Evolved UTRAN (E-UTRAN)



S6a


MME

X2

S1-MME

PCRF

S5

S1-U

119

Policy & Charging Rule Function

S11

LTE-UE

LTE-Uu

S7

IMS Serving Gateway

PDN Gateway


Function of eNodeB 3GPP Release 8, the eNB supports the following functions:

 Radio Resource Management  Radio Bearer Control  Scheduling (uplink and downlink )  Radio Admission Control  Connection Mobility Control  IP header compression and

encryption of user data stream  Selection of an MME  Routing of User Plane data towards Serving Gateway  paging messages

Each eNB will have Physical Cell Identity (PCI). There are 504 different PCIs in LTE. In addition, a globally unique cell identifier (GID) 120


Physical Cell Identity (PCI)  Non-unique. There are 504 different PCIs in LTE.

 Mobile is required to

PCI

measure the Reference Signal Received Power (RSRP) associated with a particular PCI.

PCI

 It is important to Send Report

121

detect and resolve local PCI conflicts.


EPS Bearer in LTE The QoS model in EPS is mostly based on DiffServ concepts Evolved UTRAN (E-UTRAN)


MME: Mobility Management Entity S6a MME

X2 Evolved Node B (eNB)

S7

S1-MME

Policy & Charging Rule Function PCRF

S11 S5

S1-U

IMS

LTE-Uu Serving Gateway

PDN Gateway

LTE-UE

EPS Bearer The QoS parameters associated to the bearer are: QCI, ARP, GBR and MBR 122


LTE Functional Elements - eNodeB Scheduling • Dynamic resource allocation to UE’s • Transmission of Pages & broadcast information

Network Access Security (PDCP) • IP header compression • Ciphering of user data stream

Radio Resource Management

EPC Network Selection

• Bearer & Admission control • RF Measurement Reporting

• MME Selection at UE attachment • User Plane routing to SAE-GW

eNB eNodeB

Combines the functionality of the UMTS NodeB & RNC

123


LTE Functional Elements - MME Mobility • MME Selection for Intra-LTE handovers • SGSN Selection for 3GPP I-RAT Handover

UE Tracking and Reach-ability • Tracking Area List Management (idle or active)

EPC Access • Attachment & Service Request • Security & Authentication

Bearer management

MME

• Dedicated bearer establishment • PDN GW & SAE-GW selection

Mobility Management Entity

Equivalent to the SGSN for the Control Plane

124


LTE Functional Elements – S-GW Local Mobility Anchor for Inter eNB handover

Packet routing & forwarding between EPC & eUTRAN

I-RAT Mobility Anchor Function • 3GPP 2G/3G Handover • Optimized Handover Procedures (e.g. in LTE-CDMA)

Lawful Interception

S-GW SAE Gateway

Equivalent to the SGSN for the User Plane

125


LTE Functional Elements – P-GW Charging support Policy enforcement (QoS)

UE IP address allocation

Lawful Interception

P-GW PDN Gateway

Mobility Anchor between 3GPP & non-3GPP access systems

Equivalent to the GGSN

126


Self Organising Networks (SON) The scope of Release 8 of SON:

   

Automatic Automatic Automatic Automatic

inventory software download Neighbour Relation Physical Cell ID (PCI) assignment

The next release of SON, as standardised in Release 9, will provide:

   

127

Coverage & Capacity Optimisation Mobility optimisation RACH optimisation Load Balancing optimisation


Release 8  Data Rate: Peak data rates target 100 Mbps (downlink) and 50 Mbps  (uplink) for 20 MHz spectrum allocation, assuming 2 receive antennas  and 1 transmit antenna at the terminal

128


Release 8  Latency: The one-way transit time between a packet being

available at the IP layer in either the UE or radio access network and the availability of this packet at IP layer in the radio access network/UE shall be less than 5 ms

 Also C-plane latency shall be reduced, e.g. to allow fast transition times of less than 100 ms from camped state to active state

129


Radio Resource Control (RRC) C plane signalling

RRC

u plane Data

NAS Protocol(s) (Attach/TA Update/…)

 Managing RRC connection  Mobility handling during RRC

Application Layer IP / TCP | UDP | …

 

(E-)RRC (Radio Resource Control)

RLC (Radio Link Control)


PDCP (Packet Data Convergence Protocol)


…



…



Logical Channel

  

connected mode Cell selection and re-selection Interpreting broadcast system information Managing radio bearers Measurement reporting and control Ciphering control

Signalling Radio Bearers (SRB)

 Radio bearers are used only to carry the RRC and NAS messages

Medium Access Control (MAC)

Transport Channels FDD | TDD - Layer 1 ( DL: OFDMA, UL: SC-FDMA )

130

 SRBs are divided into 3 types: 1. Signalling Radio Bearer 0: SRB0 2. Signalling Radio Bearer 1: SRB1 3. Signalling Radio Bearer 3: SRB3 © 2012 AIRCOM International Ltd


u plane Data



Admission Control






…



…



Logical Channel


Admission Control Transport Channels FDD | TDD - Layer 1 ( DL: OFDMA, UL: SC-FDMA )

131



u plane Data








…



…



The purpose of this procedure:  Establish/ Modify/ Release RBs  Perform Handover  Configure /modify measurements

Logical Channel



132



u plane Data








…



…



Logical Channel

The purpose of this procedure:  To re-establish the RRC connection  A UE in CONNECTED state in order to continue the RRC connection  This succeeds only if a valid context exists



133



u plane Data








…



…



The purpose of this procedure:

 To activate security after the RRC connection establishment, using SRB1

Logical Channel



134



u plane Data








…



…



Logical Channel

The purpose of this procedure is the release of:

 SRB  EPS Bearers  ALL Radio resources



135



u plane Data



SIBs






…



…



Logical Channel


The purpose of this procedure:

 To transmit paging information to UE in RRC IDLE State

 To inform UE in RRC IDLE about system information change


136


Signalling Radio Bearer Logical channels

DTCH

DCCH

CCCH

BCCH

Signalling Radio Bearers (SRB) are defined as Radio bearers that are used only to transmit RRC and NAS

 Signalling Radio Bearer 0:

SRB0: RRC message using CCCH logical channel.

Transport channels DL-SCH

SRB1: is for transmitting NAS messages over DCCH logical channel.


Physical channels PDSCH

137


SRB2: is for high priority RRC messages. Transmitted over DCCH logical channel © 2012 AIRCOM International Ltd

Field Results from LTE Trial Objective: The purpose of the test is to validate that the EPS is able to pass ICMP packets to/from a test server under unloaded and loaded conditions using a 5 MHz x 5 MHz FDD channel bandwidth

Max RTT Min RTT Av RTT (ms) (ms) (ms) PING NOLOAD PING LOAD

138

PING Req

PING Res

PING Loss

Success Rate

18

15

16.25

104

99

5

95.2%

168

15

20.71

109

104

5

95.2%


What Tests Need to be Done?  Latency from UE to Server using a 5 MHz x 5 MHz FDD channel bandwidth

RTT (ms)

RTT vs Payload Size 180 160 140 120 100 80 60 40 20 0

EXC RTT GOOD RTT POOR RTT

139

32 B 26.9 28.5 28.1

64 B 30.2 35.6 35.2

256 B 41.0 35.7 51.5

512 B 38.2 43.0 59.4

1024 B 41.1 43.1 155.1


Air Interface – Rel’99 CELL URA

CELLPCH

CELL SELECTION

CELL SELECTION

CELL FACH NO QoS

CELL DCH QoS

CELL SELECTION

IDLE CELL SELECTION

140


UE States – LTE RRC CONNECTED

Handover

RRC IDLE CELL SELECTION

This will reduce Latency

Question: Will there be more handovers with LTE? 141


LTE Devices – UE Categories

142


3G Services and QoS Classes  Each application is

RT Video Telephony

Telephony

Streaming Video

Radio Tuner

Web Browsing



different in nature Some are high delay

Location Services Computer Games

E-mail

Server Backups

NRT

Videotelephony

Casual

Streaming video

Critical

INTEGRITY

Streaming music

Telephony

UMTS File downloading

Web browsing

Calendar synchronisation

Teleshopping

Mail downloading

143

Teleworking


Quality of Service Traffic Class

Conversational

Streaming

Background

Maximum Bit Rate

X

X

X

X

Delivery Order

X

X

X

X

Maximum SDU Size

X

X

X

X

SDU Format Information

X

X

X

X

X

X

SDU Error Ratio

144

Interactive

Residual Bit Error Ratio

X

X

X

X

Delivery of Erroneous SDUs

X

X

X

X

Transfer Delay

X

X

Guaranteed Bit Rate

X

X

Traffic Handling Priority

X

Allocation/Retention Priority

X

X © 2012 AIRCOM International Ltd

Services/Applications Traffic Class

Conversational

Speech

X

Video Call

X

Streaming

Streaming Video

X

Streaming Audio

X

Interactive

Web Browsing

X

Email

X

Email (Background) VoIP Gaming Presence

145

Background

X X X X


LTE Quality of Service

146


LTE QoS  Allocation and Retention

Priority (ARP): Within each QoS class there are different allocation and retention priorities

 The primary purpose of ARP is

to decide whether a bearer establishment / modification request can be accepted or needs to be rejected in case of resource limitations (typically available radio capacity in case of GBR bearers)

In addition, the ARP can be used (e.g. by the eNodeB) to decide which bearer(s) to drop during exceptional resource limitations (e.g. at handover) 147


Questions 1. Give a example of layer 4 protocol? 2. Give a example of layer 3 protocol? 3. What is the function of ARP? 4. What does QCI 1 mean? 148


Questions 5. How has Latency been reduced in LTE? 6. What is meant by 4x2?

7. What is meant by GSM re-farming? 8. What is a PCI? 9. Give some of the functions of SON for Rel’8?

10. What is EPS Bearer?

149


Session 7 LTE Mobility Management

150


Air Interface – Rel’99 / Rel 4 CELL URA

CELLPCH

CELL DCH QoS

CELL FACH NO QoS

IDLE

151


LTE – Always On  In the early deployment phase, LTE coverage will certainly be restricted to city and hot spot areas.

 MORE HO’s than Rel’99 Cell DCH Connected

Handover

LTE Connected

Handover

GSM Connected

GPRS Packet Transfer

Cell FACH Connection Establishment/Release

Connection Establishment/Release Connection Establishment/Release

Cell URA Cell PCH Reselection

IDLE

152

LTE _IDLE

GSM/GPRS IDLE


UE Power-up UE Power up

DL Syn and Physical Channel ID

Acquire another LTE Cell

Find MIB – System BW MCC +MNC SIB’s supported

PLMN ID matches

PCFICH ProcessingKnows the set up of PDCCH

Retrieval of SIBs Cell Selection Parameters After Attach –Defaulf Bearer/IP adress

Cell Barred Cell Selection Successful 153

Yes Pre-amble / Attach


Cell Selection  After a UE has selected a PLMN, it performs cell selection – in other words, it searches for a suitable cell on which to camp

 While camping on the chosen cell, the UE acquires the system information that is broadcast

 Subsequently, the UE registers its presence in the tracking area,

after which it can receive paging information which is used to notify UEs of incoming calls

eNB

154

When camped on a cell, the UE regularly verifies if there is a better cell; this is known as performing cell reselection.


EPS Mobility Management Evolved Packet Core (EPC)

Evolved UTRAN (E-UTRAN)

EPS Mobility Management 2 states: EMM-DEREGISTERED EMM-REGISTERED HSS


S6a


MME

X2 S1-MME

PCRF

S11

LTE-UE

S5

S1-U

LTE-Uu

155

S7

Serving Gateway

Internet PDN Gateway


EPS Mobility Management - 2 States EMM-DEREGISTERED:

 In this state the MME holds no valid location information about the UE

MME

 Successful Attach and Tracking Area Update

(TAU) procedures lead to transition to EMMREGISTERED

EMM-REGISTERED:

• In this state the MME holds location

information for the UE at least to the accuracy of a tracking area

MME

• In this state the UE performs TAU procedures,

responds to paging messages and performs the service request procedure if there is uplink data to be sent

156


Tracking Area Update – IDLE LTE Non Access Stratum (NAS) The LTE NAS protocol software enables communication with the MME in the LTE core network and handles functions of mobility

Tracking Area Identity = MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area Code Tracking Area

Tracking Area s6a

NAS: Tracking Area update

157

MME

Home HSS


Tracking Area Update – IDLE Tracking areas are allowed to overlap: one cell can belong to multiple tracking areas TAI1 TAI1-2 TAI1 TAI1-2 TAI1 TAI2 TAI2

TAI2 TAI2 TAI2 TAI2 TAI2 TAI2

NAS: Tracking Area update

MME

TAI2 TAI2 TAI2 TAI3 TAI3 TAI3 TAI3 158


LTE Functional Nodes - Management Entity (MME) Tracking Area Update Request S-TMSI/IMSI, PDN address allocation

Tracking Area Update Accept

MME

S1-MME (Control Plane) NAS Protocols

Tracking Area Update Complete

S1-AP SCTP IP

eNB

 Tracking area (TA) is similar to

Location/routing area in 2G/3G

 Tracking Area Identity  MCC (Mobile Country Code)  MNC (Mobile Network Code)  TAC (Tracking Area Code) 159

L1/L2 S1-U (User Plane) User PDUs

GTP-U

UDP

Serving Gateway

IP L1/L2 © 2012 AIRCOM International Ltd

Globally Unique Temporary ID Globally Unique Temporary ID GUMMEI MCC + MNC + MMEI

M-TMSI

 The Globally Unique MME Identifier (GUMMEI) is constructed from the MCC, MNC and MME Identifier (MMEI).

 Within the MME, the mobile is identified by the M-TMSI.

MME

MME

160

MME POOLING


Context Request Context Request

 A context request includes

old GUTI, complete TAU request, P-TMSI, MME address etc. Basically this message is sent by new MME to old MME to inquire about UE's authenticity, the bearers created if any etc.

Context Response

 Context response include

IMSI, EPS bearers context, SGW address and etc.

Create Session Request/Response: If there was no change in SGW there will not be this message. 161


RRC States – Idle OR Connected In the early deployment phase, LTE coverage will certainly be restricted to city and hot spot areas.

Cell DCH Connected

Connection Cell Establishment/ Release

Handover

LTE Connected

Handover

GSM Connected

GPRS Packet Transfer FACH

Connection Establishment/Release

Cell URA Cell PCH

IDLE

LTE _IDLE

Connection Establishment/Release

GSM/GPRS IDLE

Cell Selection /Reselection

162


RRC IDLE Logical channels BCCH

MIB BCH

Transport channels DL-SCH

Physical channels

20Mhz BW

PBCH

163

PDSCH

MIB BW = 1.08Mhz


Physical Cell Identity (PCI) The UE moving towards a new cell and identifies the Physical Cell Identity (PCI) based on the Synchronisation signals Physical Cell Identity (PCI) = 504

P-SCH

S-SCH

 P-SCH: for cell search and identification by the UE -Carries part of the cell ID (one of 3 orthogonal sequences)

 S-SCH: for cell search and identification by the UE Carries the remainder of the cell ID (one of 168 binary sequences)

164


Cell Reselection:

Qrxlevmin SIB1

PCI

PCI

PCI

PCI

Measurement criteria

Measured neighbours S – criteria Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset)-P Compensation

Suitable neighbours

P Compensation = max(Pamax-PbMax)

R – criteria neighboring cell was ranked with the highest value R

Best ranked cell

Re-selection if not serving cell 165


LTE_ACTIVE IDLE (Cell Selection) LTE_ACTIVE idle

RRC – Idle Cell Selection done by UE Base on UE Measurements

For a cell to be suitable: S rx level>0 Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset) Q rxlevmeas RSRP (Reference Signal Received Power)

Reference signals are transmitted in ALL radio blocks

166


LTE_ACTIVE IDLE (Cell Selection) For a cell to be suitable: S rx level>0 Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset) Srx = -100 – (-80) = -20 (Will not do cell selection)

Q qrxlevmin =-80dBm

Q rxlevmeas

Q rxlevmeas=-100dBm Will not do cell selection

RSRP (Reference Signal Received Power) 167


Cell Reselection: R-Criterion PCI

PCI

PCI

PCI

Measurement criteria

Measured neighbours S – criteria

Suitable neighbours R – criteria Rs = Qmeas,s + Qhysts cell)

Best ranked cell

Rn = Qmeas,n - Qoffsets,n for candidate neighbouring cells for cell reselection 168


Cell Reselection: R-Criterion Rs = Qmeas,s + Qhysts (for the serving cell)

Rn > Rs =>“cell reselection“

RSRP (dBM)

Qmeas,n

Rn

Qmeas,s Qhysts

Rs Qoffsets,n Treselection the time interval value Treselection, whose value ranges between 0 and 31 seconds 169


Measurement Rules Measurement rules Which frequencies/ RATs to measure: high priority high priority + intra-frequency

 In RRC_IDLE, cell re-selection between frequencies is based on

absolute priorities, where each frequency has an associated priority. Cell-specific default values of the priorities are provided via system information.

 E-UTRAN may assign UE-specific values upon connection release.  In case equal priorities are assigned to multiple cells, the cells are ranked based on radio link quality.

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Handover – RRC Connected

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Handover – RRC Connected In RRC_CONNECTED, the E-UTRAN decides to which cell a UE should hand over in order to maintain the radio link. In LTE the UE always connects to a single cell only – in other words, the switching of a UE’s connection from a source cell to a target cell is a hard handover.

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Measurement Report Triggering For LTE, the following event-triggered reporting criteria are specified: Source eNodeB

 Event A1. Serving cell becomes better than absolute threshold

 Event A2. Serving cell becomes worse than absolute threshold

DCCH: RRC Measurement Control

 Event A3. Neighbour cell becomes

better than an offset relative to the serving cell

 Event A4. Neighbour cell becomes DCCH: RRC Measurement Report

better than absolute threshold

 Event A5. Serving cell becomes

worse than one absolute threshold and neighbour cell becomes better than another absolute threshold

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Measurement Report Triggering

Source eNodeB DCCH: RRC Measurement Control

For inter-RAT mobility, the following event-triggered reporting criteria are specified:

 Event B1. Neighbour cell

becomes better than absolute threshold

 Event B2. Serving cell becomes DCCH: RRC Measurement Report

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worse than one absolute threshold and neighbour cell becomes better than another absolute threshold


LTE Reference Signal Received Quality (RSRQ)  The RSRQ is defined as the ratio:

N · RSRP/(LTE carrier RSSI)  where N is the number of Resource Blocks (RBs) of the LTE carrier RSSI measurement bandwidth.

 The measurements in the numerator and denominator are made over the same set of resource blocks.

 While RSRP is an indicator of the wanted signal strength,

RSRQ additionally takes the interference level into account due to the inclusion of RSSI.

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User Plane Switching in Handover

RLC

RLC

RLC X2 Connection

RLC

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RLC

RLC


Handover Timings Source cell

1

4 2

3

1. UE identifies the target cell

2. Reporting range fulfilled 3. After UE has averaged the measurement, it sends measurement report to source eNodeB

Target cell

4. Source eNodeB sends

handover command to the UE

Event A3. Neighbour cell becomes better than an offset relative to the serving cell

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Handover The event detected and reported is the event A3 within 3GPP LTE

Source eNodeB DCCH: RRC Measurement Control

The UE makes periodic measurements of RSRP and RSRQ based

Target eNodeB DCCH: RRC Measurement Report

Handover Decision

X2: Handover Request

Admission Control X2: Handover Request Ack HO Command 178


Handover Source eNode B

Target eNode B

HO Command Forward Packets to target

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Buffer Packets


Handover - Buffer Forwarding Source eNodeB

MME

Target eNodeB

SAE

HO Command

Forward Packets to target Buffer Packets

Switch path Request

User Plane UpdateRequest

Switch DL path

Switch path Ack

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User Plane ACK


Handover Source eNodeB

In LTE, data buffering in the DL occurs at the eNB because the RLC protocol terminates at the eNB.

Therefore, mechanisms to avoid data loss during inter- eNB handovers is all the more necessary when compared to the UMTS architecture where data buffering occurs at the centralised Radio Network Controller (RNC) and inter-RNC handovers are less frequent.

DCCH: RRC Measurement Configuration

DCCH: RRC Measurement Report

Handover Decision


X2: Handover Request Ack DCCH: RRC Connection Reconfiguration

RRCConnectionReconfigurationComplete message.

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Target eNodeB


Handover Connected Mode Mobility In LTE_ACTIVE, when a UE moves between two LTE cells

DATA

User Plane TCP/UDP

Control

IP

NAS

PDCP RLC

RRC RLC

MAC

MAC

PHY

PHY

Serving Gateway

MME

GTP -C UDP IP L2 Ethernet

NAS

L1-SDH

GTP -C UDP

GTP -U UDP

IP

IP

L2 Ethernet

L2 Ethernet

L1-SDH

L1-SDH

NAS S1AP SCTP IP L2 (Ethernet)

Control NAS RRC RLC MAC PHY

S1AP SCTP IP L2 (Ethernet)

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DIRECTION S1- Control MME


Questions 1. Define the following: a) Reference Signal Received Quality (RSRQ)

b) E-UTRA RSSI

c) Reference Signal Received Power (RSRP),

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Questions 2. What is a PCI and how many are there?

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Questions 4. What is the difference between PCI and global cell ID?

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Questions 5. The total number of handovers are likely to be higher in LTE than in UMTS. Why?

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Thank you

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AIRCOM Asset LTE Basics and Asset

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