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For internal use For internal use

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LTE10, LTE11, LTE571

LTE10, LTE11, LTE571

Nidia Couto - nidia.couto@nsn.com

Nidia Couto - nidia.couto@nsn.com

The latest version of this NEI can

(2)

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LTE10 E10 --EPS EPS bearebearers for crs for conversational voiceonversational voice

LT

LTE1E11 -1 -Robust HeadeRobust Header Compressior Compressionn

LT

(3)

RL20 - LTE10 - EPS bearers for conversational voice

Table of Cont ents

1

Introduction

Motivation and Feature Overview

Main Menu

NEI Contact: Nidia Couto / Dawid Czarnecki

2

Interdependencies

Interdependencies with Other Features and Functions

3

Technical Details

Functionality and Implementation, Message Flows

5

Dimensioning Aspects

Dimensioning Impacts and Examples

4

Configuration Management

Parameters

(4)

Main Menu

Two new QCI bearers:

 ─  QCI1 bearer for transmission of voice packets

 ─  QCI5 bearer dedicated for IMS signaling

O&M switch (schedulType) allows to define whether QCI5 bearer carries IMS signaling or not

 ─  If IMS signaling is not specified for QCI5, the bearer is weighted according to QCI-specific relative weight (schedulWeight on

qciTab5)

Techni cal Details

LTE10 - EPS bearers for conversational voice - IMS signaling Table of Contents

IMS

 –

IP Multim edia Subsystem

IP Multimedia Subsystem is an access-independent architecture that enables various types of multimedia services

to mobile-users using common Internet-based protocols.

If schedulType is not set for signaling, QCI5 is weighted as a

(5)

Main Menu

To ensure QoS for voice calls, both target bit rate and delay have to be maintained

 ‒

The Flexi BTS takes the GBR signaled via S1 interface into account for Radio Resource Management ( Admission

Control and Scheduler ).

The maximum GBR for EPS bearers with QCI 1 is limited by qci1GbrLimit (default: 250kbps). EPS bearers with GBR value

higher than this will be rejected by eNB.

 Admission Control

 ‒

Due to QoS restrictions, two new thresholds for GBR bearers are introduced to radio admission control

GBR threshold for new calls: maxNumQci1Drb

GBR threshold for incoming calls: addNumQci1DrbRadioReasHo, addNumQci1DrbTimeCriticalHo

Scheduler 

 ‒

Dynamic scheduling is applied for EPS bearers with QCI 1

 ‒

The uplink and downlink scheduler use the GBR delay budget for its scheduling decisions. The delay budget can

be configured by the operator (delayTarget, schedulBSD, schedulWeight)

 ‒

Non-GBR data transmission might be reduced in order to achieve the GBR for voice users

 ‒

Voice service (as based on GBR bearers) is not subjected to rate capping functions

Techni cal Details

LTE10 - EPS bearers for conversational voice –Impacts on RRM

(6)

Main Menu

Configuration Management

LTE10 –Parameters related to Radio Admission Control

Table of Contents

QCI1-specific

parameters for different

bandwidths

Carrier BW 20MHz 15MHz 10MHz 5MHz max PRBs 100 PRBs 75 PRBs 50 PRBs 25 PRBs

used PRBs for UL-signaling (PUCCH)

19 see RRM.2691 17 see RRM.2691 10 see RRM.2691 8 see RRM.2691

Parameter  step sizerange, defaultvalue step sizerange, defaultvalue step sizerange, defaultvalue step sizerange, defaultvalue

maxNumQci1Drb 0…600 step 1 100 0…500 step 1 100 0…400 step 1 100 0…200 step 1 75 addNumQci1DrbRadioReasHo 0…600step 1 40 0…500step 1 30 0…400step 1 15 0…200step 1 15 addNumQci1DrbTimeCriticalHo 0…600 step 1 40 0…500 step 1 30 0…400 step 1 20 0…200 step 1 15

O&M thresholds for RAC interaction with BM and MM for 10 MHz*

MOC Modifiableby  Abb reviat ed name Values Descr ipt ion

LNCEL Operator     maxNumQci1Drb range: 0-400, step: 1default: 100 (for 10MHz band) Threshold for the maximum number of established QCI1-GBR-DRBs in the cell

LNCEL Operator     addNumQci1DrbRadioReasHo range: 0-400, step: 1default: 15 (for 10MHz band)

 Additional margin for the maximum number of active GBRs in the cell accessing the cell via handover with HO-cause "HO desirable for radio reasons". This margin is added to the threshold maxNumQci1Drb.

LNCEL Operator     addNumQci1DrbTimeCriticalHo range: 0-400, step: 1default: 20 (for 10MHz band)

 Additional margin for the maximum number of active GBRs in the cell accessing the cell via hand over with HO-cause: "Time Critical HO". This margin is added to the threshold maxNumQci1Drb.

Values for RL40. For earlier  releases the number of QCI1

DRBs is limited to 150 in 5MHz and 200 in other BWs.

(7)

Main Menu

GSM/LTE RF sharing at 1800 MHz

Only UL considered (limiting link)

Short retransmission delay in LTE allows for several

HARQ retransmissions within acceptable delay budget

(50..70ms total packet delay at the air interface)

 –

With the cost of reducing capacity as each retransmission

will require a new scheduler allocation.

Lowering AMR codec rate will also increase the cell range

• Gain from RoHC already included in the calculations

LTE10

 –

Coverage Aspects

No impact on coverage –Using retransmissions , HARQ gain can bring ~5dB improvement in LiBu

Table of Contents

Results slightly worse than GSM (7dBm higher power).

Further improvement can be achieved after  considering the gains of packet segmentation

(8)

Main Menu

VoIP capacity example:

Due to the big number of small packets being sent, the

bottleneck for VoIP users is not on on U-Plane, but on

C-Plane

 –

Each allocation requires a PDDCH grant

 –

For non cell edge users, grants can be reduced by

aggregating multiple packets (max 3, subjected to delay

target) and sending them all at once

 –

For user at the cell edge, each retransmission requires a

separate PDCCH grant, reducing the number of supported

users

LTE10

 –

Capacity Aspects

No impact on Cell Throughput –Number of UEs limited due to PDCCH resources

Table of Contents

 Alt ho ug h more r etrans mi ss io ns im prove robustness and coverage, increased PDCCH usage may lead to VoIP capacity degradatio n.

 Ass um pt io ns

• VoIP codec AMR12.2

• 10MHz BW

• 3 PDCCH symbols • PDCCH Alpha = 0.8

Such calculations can be performed

HARQ Gain (3 retransmissions)

(9)

RL20 - LTE11 - Robust Header Compression

Table of Cont ents

1

Introduction

Motivation and Feature Overview

Main Menu

NEI Contact: Nidia Couto / Dawid Czarnecki

2

Interdependencies

Interdependencies with Other Features and Functions

3

Technical Details

Functionality and Implementation, Message Flows

6

Dimensioning Aspects

Dimensioning Impacts and Examples

5

Benefits and Gains

Simulation, Lab and Field Findings

(10)

Main Menu

The robust header compression (RoHC) function compresses the header of IP packets for the EPS

bearer with QCI 1

RoHC is supported for IPv4 and IPv6.

The following RoHC profiles are supported (3GPP R8):

 ‒ ROHC uncompressed (RFC 4995)

 ‒ ROHC RTP (RFC 3095, RFC 4815)

 ‒ ROHC UDP (RFC 3095, RFC 4815)

 ‒

Those RoHC profiles must be supported by all IMS-voice

capable UEs (3GPP TS 36.306)

Operation takes place between 3rd and 2

nd

OSI layer 

Introduction

LTE11 - Robust Header Compression Table of Contents

320bits

(11)

Main Menu

Techni cal Details

LTE11 - Robust Header Compression –Exemplification

Table of Contents

Field predictable in the course of transmission –

“Destination IP”

IP/UDP/RTP header  consisting of predictable and

unpredictable fields -subjected to compression

MAC header, RLC header, VoIP payload, CRC checksum - not subjected

to compression 10.0.0.10 10.0.0.10 10.0.0.10 10.0.0.10 10.0.0.10 10.0.0.10 6 3 7 0 1 8 “from now on assume Destination IP is 10.0.0.10” 10.0.0.10 6 3 7 0 1 8 x Unpredictable field

Context - information about all fields that are predictable and their change patterns sent in the beginning of transmission to allow header compression

Uncompressed transmission

Compressed transmission

Initial transmission, “context” is initialized so that next transmissions can be

compressed

In the course of transmission header fields initialized in context do not have to be

(12)

Main Menu

Benefits and Gains

LTE11 - Robust Header Compression –Exemplary Call

Table of Contents

Source:

10 minutes of 12.2 kbps AMR coded VoIP call wit h talk spu rt/silent p eriod alternating every 1 second

(SID packets excluded)

ROHC header type Field description ROHC header bits Samples Samples [%] IR To initialize the context of the decompressor  504 8 0,01% IR-DYN To initialize the dynamic part of the context 120 1500 1,00% R-0 To signal 6 LSBs of RTP Sequence Number  24 118961 79,31% R-0-CRC To update reference value of RTP SN 32 17625 11,75% R-2 To signal more LSBs of the RTP SN 40 6000 4,00% R-2-Ext3 Sent when compressor does not receive ACK for R-0-CRC 56 1500 1,00% R-0-ACK Used by decompressorto acknowledge received R-0-CRC or R-2-Ext3 packets 40 4406 2,94%

TOTAL 150000 100,00%

Uncompressed header volume

IPv4/UDP/RTP packet overhead is 40 bytes

15000 packets x 40B x 8b = 4.8 x 10

7

bits

Compressed header volume

RoHC headers sizes are given in the table

504 x 8 + 120 x 1500 + … + 40 x 4406 = 4.1 x 10

6

bits

(13)

Main Menu

Representative transmission

LTE11 - Robust Header Compression Table of Contents

RoHC Header Size Distribution

75% 80% 85% 90% 95% 100% 24 32 40 56 120 504       C       D       F

RoHC header size [bits]

0% 20% 40% 60% 80% 100% 504 120 24 32 40 56 40       P       D       F

RoHC header si ze [bits]

98%

98% of RoHC headers si ze is smaller or equal to

40 bits

For link budget purp oses RoHC header size is assumed to

be 40 bits

(14)

Main Menu

Dimensioning Aspects

LTE11 - Robust Header Compression –Impact on Coverage

Table of Contents

• Enhanced Pedestrian A 5Hz (EPA05) • Equipment parameters:

 – Tx Power: eNB 40W / UE 23 dBm

 –  Antenna Gain: eNB 18 dBi / UE 0 dBi

 – Feeder Loss: DL 0.4 dB / UL 0.4 dB(feederless)

 – Noise Figure: eNB 2.2 dB / UE 7 dB

• Other features:

 – eNB: 2 Tx antennas, 2 Rx antennas (2x2 MIMO)

 – UE: 1 Tx antenna, 2 Rx antennas (MRC)

 – DL F-domain Scheduler: channel-aware

 – UL F-domain Scheduler: channel-unaware

•  Additional margins:

 – Interference margin for 50% load (~ 1…2dB)

 – 2.5 dB gain against shadowing

• IP/UDP/RTP header - 320 bits • TTI bundling –off 

RL20@10MHz(12.2 kbps, no RoHC)

RL20@10MHz(12.2 kbps, RoHC)

• Enhanced Pedestrian A 5Hz (EPA05) • Equipment parameters:

 – Tx Power: eNB 40W / UE 23 dBm

 –  Antenna Gain: eNB 18 dBi / UE 0 dBi

 – Feeder Loss: DL 0.4 dB / UL 0.4 dB(feederless)

 – Noise Figure: eNB 2.2 dB / UE 7 dB

• Other features:

 – eNB: 2 Tx antennas, 2 Rx antennas (2x2 MIMO)

 – UE: 1 Tx antenna, 2 Rx antennas (MRC)

 – DL F-domain Scheduler: channel-aware

 – UL F-domain Scheduler: channel-unaware

•  Additional margins:

 – Interference margin for 50% load (~1…2dB)

 – 2.5 dB gain against shadowing

• RoHC header - 40 bits • TTI bundling - off 

DL 171 dB*

UL 150 dB*

Propagation

• Operating Band

 – FD-LTE: 2100 MHz

• COST 231 Hata 2-slope propagation model with  –  Antenna height NB: 30m

 –  Antenna height MS: 1.5m

• Clutter dependent figures(Dense Urban / Urban / Suburban / Rural)

 – Std. dev.: 9 / 8 / 8 / 7 [dB]

 – Cell area prob.: 94.4 / 94.0 / 94.0 / 89.9 [%]

DL 171.5 dB*

UL 153 dB*

3dB gain due to less bandwidth needed

per user (lower MCS used)

(15)
(16)

RL30 - LTE571 - Controlled UL packet segmentation

Table of Cont ents

1

Introduction

Motivation and Feature Overview

Main Menu

NEI Contact: Nidia Couto / Dawid Czarnecki

2

Interdependencies

Interdependencies with Other Features and Functions

3

Technical Details

Functionality and Implementation, Message Flows

5

Dimensioning Aspects

Dimensioning Impacts and Examples

(17)

Main Menu

Packet Segmentation Algorithm is used as an extension to

Link Adaptation for Uplink coverage improvement

 ‒

The enhancement in coverage comes at the cost of cell

throughput

 ‒

Due to increased number of time allocations per packet,

PDCCH load also increases

Packet segmentation is not an event-triggered mechanism, it

is done automatically and only for UEs with poor radio

channel

 ‒

LTE571 is simply an enhancement to the existing,

non-configurable packet segmentation mechanism on Layer 2

Introduction

LTE571 - Controlled UL packet segmentation Table of Contents

TTIs m m+1 L2 SDU 304b Packet segmentation TTIs L2 SDU 152b m m+1 m+2 RLC MAC RLC MAC L2 SDU 152b 1/2 2/2 RLC MAC

Total energy per packet = 22.67dBm

Total energy per packet = 25.37dBm

Increased robustness by spreading the packet in

time domain

Padding Padding Padding

Higher  overhead

16b

(18)

Main Menu I TBSPRB 1 2 3 4 5 6 7 8 0 16 32 56 88 120 152 176 208 1 24 56 88 144 176 208 224 256 2 32 72 144 176 208 256 296 328 3 40 104 176 208 256 328 392 440 4 56 120 208 256 328 408 488 552 5 72 144 224 328 424 504 600 680 6 88 176 256 392 504 600 712 808 7 104 224 328 472 584 712 840 968 8 120 256 392 536 680 808 968   1096 9 136 296 456 616 776 936 1096   1256 10 144 328 504 680 872 1032 1224   1384

What happens with allocation when UE conditions are getting worse

(LTE571 di sabled)

1. Initially user is in good radio conditions sothere’sno need for segmentation. It occupies the minimum number of PRBs needed to transmit its data with given MCS

2.  As radio conditions worsen, AMC decreases MCS order and, consequently, more PRBs are occupied

3. MAX_NUM_PRB (from ATB) is reached and whole packet can no longer be sent at once 4. Packet is segmented. Original packet size is split into 2 packets (240b and 64b plus

header). First part is sent with limit from ATB (256b TBS), second part with the lowest possible number of PRBs to ensure transport of 80b packet (144b TBS, remaining filled with padding).

5.  As radio conditions worsen MCS order drops (AMC) and PRB usage increases 6. Further increase of #PRBs not possible - MAX_NUM_PRB (from ATB) would be

exceeded. Segmentation needed.

7. Packet is segmented again –304 bits are distributed into 3 segments (2 segments of 152b and 1 segment of 56b). 8.  As MCS cannot be further decreased, ATB has to reduce the

number of PRBs, increasing segmentation

9. Packet will be segmented as much as needed to fit into the available allocation.

10. Once MAX_NUM_PRB is reduced to 1, UE will send only RLC+MAC headers and no data

Packet Segmentation when LTE571 is disabled

LTE571 - Controlled UL packet segmentation Table of Contents

 – 1 segment  – 2 segments  – 3 segments  – 5 segments  – 8 segments  – 19 segments  – headers only

Worsening radio conditions

 Ass um pt io ns

• RLC SDU size = 304 bits

• RLC + MAC header = 16 bits

88 MAX_NUM_PRB (from ATB) MAX_NUM_PRB (from ATB) 56

Without LTE571, allocation of single PRB is allowed. This way only headers are

transmitted

32 32

(19)

Main Menu I TBSPRB 1 2 3 4 5 6 7 8 0 16 32 56 88 120 152 176 208 1 24 56 88 144 176 208 224 256 2 32 72 144 176 208 256 296 328 3 40 104 176 208 256 328 392 440 4 56 120 208 256 328 408 488 552 5 72 144 224 328 424 504 600 680 6 88 176 256 392 504 600 712 808 7 104 224 328 472 584 712 840 968 8 120 256 392 536 680 808 968   1096 9 136 296 456 616 776 936 1096   1256 10 144 328 504 680 872 1032 1224   1384

What happens with allocation when UE conditions are getting worse

(LTE571 enabled)

1. Initially user is in good radio conditions sothere’sno need for segmentation. It occupies the minimum number of PRBs needed to transmit its data with given MCS

2.  As radio conditions worsen, AMC decreases MCS order and, consequently, more PRBs are occupied

3. MAX_NUM_PRB (from ATB) is reached and whole packet can no longer be sent at once 4. Packet is segmented. Original packet size is split into 2 packets (240b and 64b plus

header). First part is sent with limit from ATB (256b TBS), second part with the lowest possible number of PRBs to ensure transport of 80b packet (144b TBS, remaining filled with padding).

5.  As radio conditions worsen MCS order drops (AMC) and PRB usage increases 6. Further increase of #PRBs not possible - MAX_NUM_PRB (from ATB) would be

exceeded. Segmentation needed.

7. Packet is segmented again –304 bits are distributed into 3 segments (2 segments of 152b and 1 segment of 88b). 40b padding need to be added to fulfill  ulsMinTbs.

8.  As MCS cannot be further decreased, ATB has to reduce the number of PRBs, increasing segmentation

9. Once the minimum number of PRBs is reached (ulsMinRbPerUe >MAX_NUM_PRB), no further  segmentation is possible, even if MAX_NUM_PRB is reduced.

10. UE will keep been allocated ulsMinRbPerUe and sending at least ulsMinTbs bits of data

Packet Segmentation when LTE571 is enabled

LTE571 - Controlled UL packet segmentation Table of Contents

 – 1 segment  – 2 segments  – 3 segments  – 5 segments

Worsening radio conditions

 Ass um pt io ns

• RLC SDU size = 304 bits

• RLC + MAC header= 16 bits

88

MAX_NUM_PRB (from ATB)

New parameters introduc ed

•   ulsMinTbs = 72 bits

•   ulsMinRbPerUe = 4

LTE571 stablishes a minimum TBS and PRB number to control generated

overhead

MAX_NUM_PRB (from ATB)

(20)

Main Menu

ELSE:

redBwMinRbUl <= PRB

UE

<= min(redBwMaxRbUl, PRB

BSR

, MAX_NUM_PRB)

redBwMinRbUl<= PRB

UE

<= min(redBwMaxRbUl, MAX_NUM_PRB)

redBwMinRbUl<= PRB

UE

<= min(redBwMaxRbUl, MAX_#_PRB_SR, MAX_NUM_PRB)

PRB assignment

 –

New condit ion intro duced

LTE571 - Controlled UL packet segmentation Table of Contents

IF ulsMinRbPerUe >= MAX_NUM_PRB :

PRB

UE

= max( redBwMinRbUl, PRB_ulsMinTbs, ulsMinRbPerUe)

Minimum number of PRBs per UE

(LTE571)

Ordinary Scheduled UEs

Candidate Set 3 UEs

UEs having Scheduling Request scheduled

max(redBwMinRbUl, PRB_ulsMinTbs) <= PRB

UE

<= min(redBwMaxRbUl, PRB

BSR

, MAX_NUM_PRB)

max(redBwMinRbUl, PRB_ulsMinTbs) <= PRB

UE

<= min(redBwMaxRbUl, MAX_NUM_PRB)

max(redBwMinRbUl, PRB_ulsMinTbs) <= PRB

UE

<= min(redBwMaxRbUl, MAX_#_PRB_SR, MAX_NUM_PRB)

Without LTE571

If LTE571 is enabled, PRB allocation is limited by ulsMinRBPerUe, whenver 

MAX_NUM_PRB is too small

Number of PRBs based on min TBS and MCS order 

(LTE571)

Numberof PRBs based on min TBS and MCS order 

(LTE571)

redBwMinRbUl - Minimum number of PRBs assigned in UL

redBwMaxRbUl - Maximum number of PRBs assigned to a UE scheduled in UL

Without LTE571 upper limit for PRB allocation is always coming from ATB

(21)

Main Menu

Sending packet segments in consecutive TTIs allows more energy per voice packet to be

aggregated, increasing coverage

The coverage gain achieved with packet segmentations grows with each segmentation

operation, as well as L2 overhead

 ‒ However the gain does not grow linearly, the smaller the segment, the lower the gain

Dimensioning Aspects

LTE571 - Controlled UL packet segmentation –Coverage Gain

Table of Contents

Packet segmentation can provide up to ~5 dB coverage gain (by sacrific ing capacity) Real gains will depend on used codec, Link  Adap tat io n set ti ng s and nu mb er of seg men tatio ns

 Ass um pt io ns

•   ulsMinTbs = 72 bits

•   minRbPerUe = 4

• VoIP codec = AMR12.2

• UE Tx power = 23dBm

Depending on E-ULLA settings and the desired

configuration, ul sMinRBPerUe and ulsMinTbs

have to be set accordingly

Simulations performed by System Architecture suggest following values as most optimized*:

ulsMinRBPerUe = 3

ulsMinTbs = 104

(22)

Main Menu

Since the maximum number of supported VoIP users depends

mostly on PDCCH resources, it significantly drops with the increase

of segmentation order 

 ‒

Each segment (and HARQ retransmission) will require a new PDCCH

allocation and a new PHICH in DL (for transmission of ACKs/NACKs

per segment).

The higher the achieved coverage gain, the greater is the capacity

loss, which is why the most robust configurations are generally not

used

Dimensioning Aspects

LTE571 - Controlled UL packet segmentation –Capacity Loss

Table of Contents

Gain pr ovided by packet segmentation c omes

at the cost of the cell capacity

 Assu mp ti on s*

•   ulsMinTbs = 72 bits •   minRbPerUe = 4

• VoIP codec = AMR12.2

• UE Tx power = 23dBm

• 10 MHz Bandwidth

(23)

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