00-Wcdma Hsdpa Principles

7/28/2019 00-Wcdma Hsdpa Principles

1/29

www.huawei.com

Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Gii thiu HSDPAISSUE 1.0


2/29

Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page1

Contents

1. Khi nim v HSDPA

2. Cc k thut cho HSDPA


3/29


WCDMA Evolution


4/29


Phin bn 99 D liu gi

D liu gi c x l th no trong phin bn 99 (FDD)

DCH ( Knh c gn )

M tri ph c gn cho mi ngi dng

Vng iu khin cng sut kn Chuyn giao mm

FACH ( Knh chung )

M tri ph chung

Khng c vng iu khin cng sut kn

Khng c chuyn giao mm


5/29


Release 99 Downlink Limitation

Dedicated Channel Features ( DCH )

Maximum implemented downlink of 384kbps

OVSF code limitation for high data rate users

Rate switching according to burst throughput is slow

Outer loop power control responds slowly to channel

Common Channel Features ( FACH )

Good for burst data application

Only low data rates supported

Fixed transmit power


6/29


High Speed Downlink Packet Access (HSDPA)

The differences between HSDPA and R99

Set of high data rate channel

Channels are shared by multiple users

Each user may be assigned all or part of the resource every 2 ms

Node B

HS-PDSCH


7/29



How will HSDPA figure out the limitations of R99

Adaptive modulation and coding

Fast feedback of Channel condition

QPSK and16QAM

Channel coding rate from 1/3 to 1

Multi-code operation

Multiple codes allocated per user

Fixed spreading factor

NodeB fast Scheduling

Physical Layer HARQ ( Hybrid Automatic Repeat reQuest )


8/29



Comparison Summary


9/29


Contents

1. HSDPA Concepts

2. HSDPA Key Techniques


10/29


HSDPA Key Techniques

AMC (Adaptive Modulation & Coding)

Data rate adapted to radio condition on 2ms

Fast Scheduling based onCQI and fairness

Scheduling of user on 2ms

HARQHybrid automatic repeatrequestwith Soft combing

Reduce round trip time

16QAM

16QAM in complement to QPSKfor higher peak bit rates

SF16, 2ms and CDM/TDM

Dynamic shared in Time and code domain

3 New Physical Channels

Block 1 Block 2Block 1

Block 1?

Block 1Block 1?

+


11/29


Adaptive Modulation and Coding ( AMC )

AMC ( Adaptive Modulation and Coding ) based on CQI ( Channel

Quality Indicator )

Adjust data rate to compensation channel condition

Good channel condition higher data rate

Bad channel condition lower data rate

Adjust channel coding rate to compensation channel condition

Good channel condition channel coding rate is higher e.g. 3/4

Bad channel conditionchannel coding rate is lower e.g. 1/3

Adjust the modulation scheme to compensation channel condition

Good channel condition high order modulation scheme e.g. 16QAM

Bad channel condition low order modulation scheme e.g. QPSK


12/29


Adaptive Modulation and Coding ( AMC )

AMC ( Adaptive Modulation and Coding ) based on CQI

( Channel Quality Indicator )

CQI ( channel quality indicator )

UE measures the channel quality and reports to NodeB every

2ms or more cycle

NodeB selects modulation scheme ,data block size based on CQI

Bad channel condition

More powerNode B Node B

Power Control Rate Adaptation

Good channel condition

Bad channel condition

Good channel condition

less power

low data rate

high data rate


13/29


CQI mapping table for UE category 10

CQI value TransportBlock Size

Number ofHS-PDSCH

Modulat ion Reference pow eradjustment

0 N/A Out of range

1 137 1 QPSK 0

2 173 1 QPSK 0

13 2279 4 QPSK 0

14 2583 4 QPSK 0

15 3319 5 QPSK 0

16 3565 5 16-QAM 0

17 4189 5 16-QAM 0

18 4664 5 16-QAM 0

28 23370 15 16-QAM 0

29 24222 15 16-QAM 0

30 25558 15 16-QAM 0


14/29


HSDPA UE Categories

UE Category Maximum

Number of HS-

DSCH Codes

Received

Minimum Inter-

TTI Interval

Maximum Number of Bits of an

HS-DSCH Transport Block

Received Within an HS-DSCH

TTI

Total Number of Soft

Channel Bits

Category 1 5 3 7298 19200

Category 2 5 3 7298 28800

Category 3 5 2 7298 28800

Category 4 5 2 7298 38400

Category 5 5 1 7298 57600

Category 6 5 1 7298 67200

Category 7 10 1 14411 115200

Category 8 10 1 14411 134400

Category 9 15 1 20251 172800

Category 10 15 1 27952 172800

Category 11 5 2 3630 14400

Category 12 5 1 3630 28800


15/29


Hybrid Automatic Repeat reQuest

( HARQ )

Conventional ARQ

In a conventional ARQ scheme, received data blocks that can not be

correctly decoded are discarded and retransmitted data blocks are

separately decoded

Hybrid ARQ

In case of Hybrid ARQ with soft combining, received data blocks that

can not be correctly decoded are not discarded. Instead the

corresponding received signal is buffered and soft combined with later

received retransmission of information bits. Decoding is then appliedto the combined signal.


16/29



( HARQ )

Example for HARQ

The use of HARQ with soft combining increases the effective

received Eb/Io for each retransmission and thus increases the

probability for correct decoding of retransmissions, compare to

conventional ARQ


17/29



( HARQ )

There are many different schemes for HARQ with soft

combining.

These scheme differ in the structure of retransmissions and

in the way by which the soft combining is carried out at the

receiver

In case of Chase combining ( CC ) each retransmission is an

identical copy of the original transmission

In case of Incremental Redundancy ( IR ) each retransmission

may add new redundancy


18/29



( HARQ )

Example for Chase Combining ( CC ) Scheme


19/29



( HARQ )

Example for Incremental Redundancy ( IR ) Scheme


20/29


Fast Scheduling

Fast scheduling is about to decided to which terminal the shared

channel transmission should be directed at any given moment


21/29


Short TTI (2ms)

Shorter TTI ( Transmission Time Interval ) is to reduce RTT

( round trip time )

Shorter TTI is necessary to benefit from other functionalities

such as AMC, scheduling algorithm and HARQ


22/29


In HSDPA, a new DL transport channel is introduced call

HS-DSCH. The idea is that a part of the total downlink code

resource is dynamically shared between a set of HSDPA

users

Shared Channel Transmission


23/29


24/29


Higher-Order Modulation


25/29


HSDPA New Physical Channels


26/29


HSDPA Physical Layer Channels

New HSDPA Channels

High Speed Downlink shared Channel ( HS-DSCH )

Downlink Transport Channel

High Speed Shared Control Channel ( HS-SCCH )

Downlink Control Channel

High Speed Physical Downlink Shared Channel ( HS-PDSCH )

Downlink Physical Channel

High Speed Dedicated Physical Control Channel ( HS-DPCCH )

Uplink Control Channel


27/29


Theoretical HSDPA Maximum Data Rate

Theoretical HSDPA Maximum data rate is 14.4Mbps

How do we get to 14.4Mbps ?

Multi-code transmission

NodeB must allocate all 15 OVSF codes ( SF =16 ) to one UE

Consecutive assignments using multiple HARQ process

NodeB must allocate all time slots to one UE

UE must decode all transmission correctly on the first transmission

Low channel coding gain

Effective code rate = 1 Requires very good channel conditions to decode

16QAM

Requires very good channel condition


28/29


Implementation of MAC-hs

HS-DPCCHdemodulation and

decode

SRNC(MAC-d)

power monitor

CQI adjustment

Scheduler

Queues/flow

control

HARQ

TFRC

Power

management

Coding

andmodulation

OM

parametersPower limitation

Power for HSDPA

CQI Value

Stat. Of ACK/NACKACK/NACK

Waiting time

Queue filling infoQueue priority

CQI Value

Code

allocationCode available

Data flow

Control signal


29/29

Thank You

00-Wcdma Hsdpa Principles

Documents

Transcript of 00-Wcdma Hsdpa Principles