HSDPA concepts and strategic issues.ppt

8/11/2019 HSDPA concepts and strategic issues.ppt

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HSDPA concepts

April 2008

Oussama Akhdari

ROSI / INTPS / NAD / RASQ / International Radio support


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2 Groupe France TlcomHSDPA concepts & strategic issues / April 2008 /confidential/Oussama Akhdari

Introduction

Architecture and Main features of HSDPA

Resource Allocation Strategy

UE Categories

Conclusion

Agenda


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Why do we need HSDPA?

The PS traffic is bursty with a considerable variations on the instantaneous

bit rate and the use of the radio resources

Allocating dedicated resources as in R99 results in a waste of radioresources

Higher throughput needed to improve the user perception & to implement

new services to compete with other technologies WiMax/WiFi

Maximize the use of the available resources (power)

Need for a very dynamic adaptation of radio resources allocation

HSDPA in release 5 for the DL

HSUPA for the UL in release 6/7out of the scope of this presentation


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Introduction

Architecture & Main features of HSDPA


UE Categories

Conclusion

Agenda


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HSDPAGeneral Principle

Channel quality information

UE 1

UE 2

L1 Feedback

L1 Feedback

Data

Data

UE 1

UE 2

L1 Feedback

L1 Feedback

Data

Data

UE 1

UE 2

L1 Feedback

L1 Feedback

Data

Data

UE 1

UE 2

L1 Feedback

L1 Feedback

Data

Data

Shared DL data channel

Error correction Ack / Nack

Fast link adaptation

QPSK or 16QAM

Short Transmission Time

Interval: 2 ms2 ms

Fast Radio Channel

Dependent Scheduling

New Channels

for Traffic and

signaling


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HSDPA channels i

U

Node

AssociatedD

PCH

AssociatedDPCH

1-15xHS-PDSCH

1-4xHS-SC

CH

HS-DPCCH

HS-PDSCH:High-Speed PhysicalDownlink SharedChannel.

HS-SCCH:High-Speed SharedControl

Channel.

Associated DPCH:Dedicated Physical

Channel.

Associated DPCH:Dedicated Physical

Channel

HS-DPCCH:High-Speed Dedicated

Physical Control Channel

Rel99DCH

..

HSDPA

UL Channels

DL Channels

Physical channels


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Channels mapping

Note that the HSDPA impacts only the physical and transport levels, so there is no

new logical channels

CN RNC NodeB UEDPCCH

DPCHD PDCH

HS- DPCCH

DCH

DCH

HS-SCCH

HS-PDSCHHS-DSCH

DCCH

DCCH

DCCH

DCCH

DTCH

DTCH

DTCH

Interactive PS RAB

Interactive PS RAB

Interactive PS RAB

NAS

NAS

RRC

User 1

User 2

User n

For eachuser

Radio Access Bearers Logical ChannelsTransport Channels Physical Channels


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HS-DSCH High-Speed Dedicated Shared Channel

HS-DSCH is the transport channel used for data transmission on the

downlink and is shared by all users in the cell.

The code resource sharing is done in the time domain on a 2 ms timebasis (TTI).

Up to 4 users could be scheduled on same TTI

The shared code resource consists of 15 channelization codes with fixedspreading factor SFHS-DSCH= 16, in this time frame.

The HS-DSCH cannot be in soft/softer handover and no fast power control

is used.

The HS-DSCH uses all the excess power from the available transmission

power at the base station left from the common and dedicated channels in

Shared Carrier scenario


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HS-SCCH: High-Speed Shared Contr ol Channel

HS-SCCH is a downlink physical channel used to carry HS-DSCH

related control signaling (Physical Layer signaling).

It is shared among the HSDPA users on time division basis (TTI), with

the same scheduling as for HS-DSCH.

All UEs listen to the same HS-SCCH channel and after decoding,

decide whether the information to start listening the HS-PDSCH was

intended to that UE.

Informs the UE about

HS-DSCH code set

Modulation scheme (QPSK/16QAM)

HS-DSCH transport format (number of transport blocks per TTIand number of bits per transport block)

Hybrid ARQ information

Never in soft handover

The HS-SCCH has a spreading factor SFHS-DSCH= 128


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A-DCH: Associated Dedicated Channel

One A-DCH pair is set up for every HSDPA user in connected state.

It is used for control signaling (RRC and NAS) in uplink and downlink.

In the uplink A-DCH is also used as the channel for data transmission,where the rate can be either 384 kbps or 64 kbps.

The uplink data rate 384 kbps is selected as first priority and 64 kbps isused as a fall back rate if the path loss is judged to be too large or 384

kbps radio bearer setup fails for any reason (e.g. lack of radio orhardware resources).

The uplink A-DCH channel also contains the High-Speed Dedicated

Physical Control Channel (HS-DPCCH),the new physical channel thatcarries the L1 related signaling in uplink.


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HS-DPCCH: High-Speed Dedicated Physical Control Channel

It is used for transmitting the following information from UE to NodeB:HARQ acknowledgement (1 bit coded in 10)

Channel quality indicator (5 bits coded to 20 bits in 2 slots)

channel quality measurements based on CPICH

reporting rate is configurable through RRC/NBAP signaling

information reflecting the instantaneous downlink radio channelconditions to assist the RBS in the transport format selection (fastlink adaptation) and the scheduling

The A-DCH both UL and DL can be in soft/softer handover whilst the HS-

DPCCH can never be in soft handover


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Higher Order Modulation

16QAM

Twice the data rate compared to QPSK (used in R99)

Making optimal use of good channel conditions (high C/I)

Close to cell site Low speed

Little or no dispersion

16QAM

4 bits/symbol

QPSK

2 bits/symbol


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Fast Retransmissions

With Soft Combining

Rapid retransmissions of erroneous dataRetransmission processed in RBS

Reduced round trip delay on air interface

Soft combining of multiple transmission attempts in UE

Improved performance

Fast and Efficient Re-transmission

Fast Hybrid Acknowledgement Request (ARQ) with Soft Combining

Transmitter

Receiver


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Short TTI Transmission Time Interval

Reduced air-interface delay

Improved end-user performance

HSDPA features operate at 500 times per second

Fast Link Adaptation

Fast hybrid Automatic Repeat Request (ARQ) with soft combining

Fast Channel-dependent Scheduling

10 ms

20 ms

40 ms

80 ms

Earlier releases

2 ms


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Fast Link Adaptation in HSDPA

0 20 40 60 80 100 120 140 160-2

02

468

101214

16

Time [number of TTIs]

QPSK1/4

QPSK2/4

QPSK3/4

16QAM2/4

16QAM3/4

InstantaneousEsNo[dB] C/I received by

UE

Linkadaptation

mode

C/I varies

with fading

NodeB adjusts linkadaptation mode with a fewms delay based on channelquality reports from the UE


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Link Adaptation "AMC"Adaptive Modulation & Coding

Modulation: QPSK or 16QAM, various coding rates

Quality feedback:UEs periodically report Channel Quality Indicators (CQI)to the nodeB, based on BLERtarget, to indicate the DL channel quality

AMC consists in selecting Modulation and Coding Scheme (MCS) in the

Node B based on the CQI reported by the UE

Increase instantaneous

bit rate

16-QAM5356516

16-QAM152555830

QPSK5331915

QPSK3126210

QPSK26507

QPSK11732

QPSK11371

ModulationNumber ofHS-PDSCH

Transport blocksize

CQIvalue

16-QAM5356516

16-QAM152555830

QPSK5331915

QPSK3126210

QPSK26507

QPSK11732

QPSK11371

ModulationNumber ofHS-PDSCH

Transport blocksize

CQIvalue

M d l tiN b f HSDPAAi i t f bl kT t bl k iCQI

M d l tiN b f HSDPAAi i t f bl kT t bl k iCQI


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18 Groupe France TlcomHSDPA concepts & strategic issues / April 2008 /confidential/Oussama Akhdari16-QAM15288002555830

16-QAM15288002422229

16-QAM15288002337028

16-QAM15288002175427

16-QAM12230401723726

16-QAM10192001441125

16-QAM8153601141824

16-QAM713440971923

16-QAM59600716822

16-QAM59600655421

16-QAM59600588720

16-QAM59600528719

16-QAM59600466418

16-QAM59600418917

16-QAM59600356516

QPSK54800331915

QPSK43840258314

QPSK43840227913

QPSK32880174212

QPSK32880148311

QPSK32880126210

QPSK219209319

QPSK219207928

QPSK219206507

QPSK19604616

QPSK19603775

QPSK19603174

QPSK19602333

QPSK19601732

QPSK19601371

ModulationNumber of HSDPA

codes

Air interface block

size [bit]

Transport block size

[bit]

CQI

16-QAM15288002555830

16-QAM15288002422229

16-QAM15288002337028

16-QAM15288002175427

16-QAM12230401723726

16-QAM10192001441125

16-QAM8153601141824

16-QAM713440971923

16-QAM59600716822

16-QAM59600655421

16-QAM59600588720

16-QAM59600528719

16-QAM59600466418

16-QAM59600418917

16-QAM59600356516

QPSK54800331915

QPSK43840258314

QPSK43840227913

QPSK32880174212

QPSK32880148311

QPSK32880126210

QPSK219209319

QPSK219207928

QPSK219206507

QPSK19604616

QPSK19603775

QPSK19603174

QPSK19602333

QPSK19601732

QPSK19601371

ModulationNumber of HSDPA

codes

Air interface block

size [bit]

Transport block size

[bit]

CQI

Category11

&12

Category1

to6

Cate

gory7&8

Category

10

CQI range per UE cat


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Link Adaptation "H-ARQ"

Principle: use soft buffer in mobile to store the successive transmissions and

combine them

Temporal diversity gain

Complexity in mobile: buffer size and processing capabilities

Two schemes for HARQ:

Chase combining: same data is retransmitted and soft added to theprevious one.

Incremental redundancy: redundancy bits are added in the successiveretransmissions

Choice of Modulation & Coding SchemeMay be imperfect, due to:

Delays in CQI reporting

Errors in channel quality estimation or transmission


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HIGH CQI

CQI

TFRC, Modul,

Codes

CPICH

HSDPA Link Adaptation OperationCQI mapping table for UE categories 6

Number of

CQI valueTransportBlock Size

# MAC-dPDUs

per TrBlk

RLC Throughput per HS-PDSCH HS-PDSCH Modulation

0 N/A Out of range

1 137 0 0 kbps 1 QPSK

2 173 0 0 kbps 1 QPSK

3 233 0 0 kbps 1 QPSK

4 317 0 0 kbps 1 QPSK

5 377 1 144 kbps 1 QPSK

6 461 1 144 kbps 1 QPSK7 650 1 144 kbps 2 QPSK

8 792 2 288 kbps 2 QPSK

9 931 2 288 kbps 2 QPSK

10 1262 3 432 kbps 3 QPSK

11 1483 4 576 kbps 3 QPSK

12 1742 5 720 kbps 3 QPSK

13 2279 6 864 kbps 4 QPSK

14 2583 7 1008 kbps 4 QPSK

15 3319 9 1296 kbps 5 QPSK

16 3565 10 1440 kbps 5 16-QAM

17 4189 12 1728 kbps 5 16-QAM

18 4664 13 1872 kbps 5 16-QAM

19 5287 15 2160 kbps 5 16-QAM

20 5887 17 2448 kbps 5 16-QAM

21 6554 19 2736 kbps 5 16-QAM

22 7168 21 3024 kbps 5 16-QAM

23 7168 21 3024 kbps 5 16-QAM

24 7168 21 3024 kbps 5 16-QAM

25 7168 21 3024 kbps 5 16-QAM

26 7168 21 3024 kbps 5 16-QAM

27 7168 21 3024 kbps 5 16-QAM

28 7168 21 3024 kbps 5 16-QAM

29 7168 21 3024 kbps 5 16-QAM

30 7168 21 3024 kbps 5 16-QAM

Power(W)

CPICH

CCH

HS-SCCH

HS-DSCH

Pmax

Headroom


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21Groupe France TlcomHSDPA concepts & strategic issues / April 2008 /confidential/Oussama Akhdari

TFRC, Modul,

Codes

LOW CQI

CQI,

ACK/NAC

K

CPICH

HSDPA Link Adaptation Operation

CQI mapping table for UE categories 6

Number of

CQI valueTransport

Block Size

# MAC-dPDUs

per TrBlk

RLC Throughput per HS-

PDSCH HS-PDSCH Modulation

0 N/A Out of range

1 137 0 0 kbps 1 QPSK

2 173 0 0 kbps 1 QPSK

3 233 0 0 kbps 1 QPSK

4 317 0 0 kbps 1 QPSK

5 377 1 144 kbps 1 QPSK6 461 1 144 kbps 1 QPSK

7 650 1 144 kbps 2 QPSK

8 792 2 288 kbps 2 QPSK

9 931 2 288 kbps 2 QPSK

10 1262 3 432 kbps 3 QPSK

11 1483 4 576 kbps 3 QPSK

12 1742 5 720 kbps 3 QPSK

13 2279 6 864 kbps 4 QPSK

14 2583 7 1008 kbps 4 QPSK

15 3319 9 1296 kbps 5 QPSK

16 3565 10 1440 kbps 5 16-QAM

17 4189 12 1728 kbps 5 16-QAM

18 4664 13 1872 kbps 5 16-QAM

19 5287 15 2160 kbps 5 16-QAM

20 5887 17 2448 kbps 5 16-QAM

21 6554 19 2736 kbps 5 16-QAM

22 7168 21 3024 kbps 5 16-QAM

23 7168 21 3024 kbps 5 16-QAM

24 7168 21 3024 kbps 5 16-QAM

25 7168 21 3024 kbps 5 16-QAM

26 7168 21 3024 kbps 5 16-QAM

27 7168 21 3024 kbps 5 16-QAM

28 7168 21 3024 kbps 5 16-QAM

29 7168 21 3024 kbps 5 16-QAM

30 7168 21 3024 kbps 5 16-QAM

CPICH

CCH

HS-SCCH

HS-DSCH

Pmax

Headroom

Power(W)


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23Groupe France TlcomHSDPA concepts & strategic issues / April 2008 /confidential/Oussama Akhdari

Introduction Architecture & Main features of HSDPA


UE Categories

Conclusion

Agenda


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24 Groupe France Tlcom

HSDPA concepts & strategic issues / April 2008 /confidential/Oussama Akhdari

Packet Scheduling

Packet scheduling in the node B:

Handle by the MAC-hs entity

At each TTI, chooses the most appropriate UE to which data will betransmitted

Exploits multi-user diversity (take advantage of fast fading)

Very strong impact on performances

Several types of algorithms for Packet Scheduling:

Fair throughput: lower cell throughput, but equal data rate for UEs

Fair time: higher throughput for users near the BS, higher cellthroughput than with fair throughput

Max C/I: maximum cell throughput, but some UEs may be not servedProportional-Fair: find a compromise between efficiency and fairness


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Fast Channel-dependent Scheduling

Examples of scheduling algorithms

Round Robin (RR)

Cyclically assign the channel to users without taking channelconditions into account

Simple but poor performance

Max C/I

Assign the channel to the user with the best channel quality

High system throughput but not fair

Proportional Fair (PF)

Assign the channel to the user with the best relative channel

qualityHigh throughput, fair


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Code Tree & Multi-code operation

Code tree allocation

TDM: One user per TTICDM: Multi-user per TTI

SF = 2 4 8 16

Up to 15 codes

can be allocated to

HS-DSCH

Codes with SF>16 allocated to:

- R99/4 channels- HS-SCCH- Dedicated channels associated

to HS-DSCH

Less codes can be allocated to

HS-DSCH to provide more space

for R99 channel

time

UE3codes UE1 UE2

1 TTI

Multi-user / TTI operation


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Link Adaptation & Code Multiplexing

2

ms

CODE

S

HS-PDSCH

SCHEDULE

R

HIGH CQI

LOW CQI

CQI

CQI

TFRC

TFRC

MAC-HS

user

packet

data blocks

CPICH

CCH

HS-SCCH UE2

HS-DSCH UE1

Pmax

Headroom

HS-SCCH UE1

HS-DSCH UE2

UE1

UE2

Power(W)


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Power allocation

Use of power

2 possible solutions:

Fixed amount of power for HSDPA channels

OR use only the available power after power allocation for DCH

t HS-DSCH with dynamic power allocationt

DCH (power controlled)

Common channels

HS-DSCH (rate controlled)

Totalcell

power

Power

HS-DSCH with static power allocation


Common channels

Totalcell

power

Power

HS-DSCH (rate controlled) power

Unused power

HS-DSCH with dynamic power allocationt


Common channels


Totalcell

power

Power

t


Common channels


Totalcell

power


Common channels

HSDPA (rate controlled)

Totalcell

power

Totalcell

power

Power

HS-DSCH with static power allocation


Common channels

Totalcell

power

Totalcell

power

Power

HSDPA (rate controlled) power

Unused power

Waste of unused power Profit from the unused

power by R99


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UE Categories

Conclusion

Agenda


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UE Capabilities

Several Categories are defined

Each category corresponds to a maximum bit rate supported byHSDPA Terminal

TS 25.306 presents 12 Categories but more categories may beadded at later stages

1

2

1

1

1

3

3

Min inter-TTI

interval

27952QPSK, 16QAM1510

3630QPSK512

3630QPSK511

7298QPSK, 16QAM56

7298QPSK, 16QAM55

7298QPSK, 16QAM52

7298QPSK, 16QAM51

Max number of HS-

DSCH bits received

within an HS-DSCH TTI

ModulationMax number of

HS-DSCH codes

received

UE category

1

2

1

1

1

3

3

Min inter-TTI

interval

27952QPSK, 16QAM1510

3630QPSK512

3630QPSK511

7298QPSK, 16QAM56

7298QPSK, 16QAM55

7298QPSK, 16QAM52

7298QPSK, 16QAM51

Max number of HS-

DSCH bits received

within an HS-DSCH TTI

ModulationMax number of

HS-DSCH codes

received

UE category


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UE Categories

Conclusion

Agenda


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Conclusion

HSDPA improves the overall spectral efficiency and DL throughput

3.6 Mbps as peak data rate for 1st UE (1 UE during one TTI inbest radio conditions)

10 Mbps as peak data rate for enhanced UE (1 UE during oneTTI in best radio conditions)

A high throughput is tightly linked to thePower resources

Deployment strategy

Resource Allocation Strategy (Link Adaptation, Scheduling, .).

UE categories in use

Current load of the cell.


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HSDPA concepts and strategic issues.ppt