hsdpa basic principles

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Basic Principlesa in Understanding HSDPA Technology

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Security Level: Internal Use Only

HSDPA Basic Principlewww.huawei.com

HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Learning ObjectivesHSDPA basic principle and feature HSDPA key technologies HSDPA physical channels

HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 1

Contents

Chapter 1 HSDPA Basic Concepts and Characteristics Section 2 Key Techniques Section 3 Physical Channel

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Huawei Confidential

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HSDPA Basic ConceptsHSDPA = High Speed Downlink Packet Access Important Features of 3GPP R5 Why HSDPA?The subscribers request higher speed and better quality data access Competition challenge from CDMA EV/DO, WiMAX Up to now, the throughput request for downlink is much more higher than that of uplink The channel configuration of R99 lead a very low efficiency on the downlink capacity

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HSDPA CharacteristicsHSDPA is the solution of WCDMA offering higher speed downlink data services.Peak data rate in DL: 14.4Mbps (physical layer) Shorter delay Higher efficiency using downlink code and power and bigger downlink capacity Flexible cell resource allocation More high speed user accessHSDPAUMTS R9 9

GS M

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Contents

Chapter 1 HSDPA Basic Concepts and Characteristics Chapter 2 Key Techniques Chapter 3 Physical Channel

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HSDPA Key Techniques- Overview

AMCAdaptive Modulation and Coding

HARQ (Hybrid ARQ)Hybrid Automatic Repeat Request

Fast Scheduling

SF16, 2ms and CDM/TDM

16QAM

3 New Physical Channels

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HSDPA Key TechniquesFast Scheduling(2ms short frame and scheduling) AMC (support QPSK and 16QAM) HARQ

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Fast Scheduling BasicPhysical Layer BasicIf a little part of received 10ms frame (15 slots - R99) cant be decoded correctly, whole frame will be retransmit 10ms later.

An HSDPA frame is only 2ms(3 slots). If a 2ms frame cant be decoded correctly, just this 2ms frame need be retransmitted. Other 2ms(up to 6) HARQ process may continue transmitting data, thus radio resource could be used more effectively.

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Fast SchedulingBy fast scheduling, HSDPA cell can allocate the available HSDPA power resource and code resource among users effectively, to improves the throughout.

Scheduling Principle: based on channel condition in short period; based on balance between throughout and proportional fair for all users in long period.

Scheduler may works based on CDM and/or TDMChannel condition Amount of data waiting in the queue (delay) Fairness Cell throughout, etc

Some basic schedulerRound Robin (RR) Maximum C/I (MAXC/I) Proportional Fair (PF)

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Share and Scheduling of Shared ChannelThe following fig describes scheduling processing for 4 users.

All codes reserved for HSDPA transmission 2ms

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Fast Scheduling ProcessAvailable resource Transmit power for which users Required resource Temporary statistic

Scheduling Algorithm

Channelization code Data attributes

Input: 1. Available resource: power and channelization code 2. Required resource: including users, user data, retransmission, air interface ability estimate, etc. 3. Temporary statistic of scheduling algorithm: waiting time, average C/I, etc. Output: Transmit power for which users, power, channelization code, data attributes

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Max C/I Scheduling Algorithm

Features: 1) Allocates channel to the user with max C/I in one TTI. 2) Provides the highest cell throughout, because channel is allocated to the user in the best radio condition . 3) It is not fair for the users located in areas of poor coverage. By max C/I algorithm, the system hardly allocate channel for users under pool signal condition.

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RR Scheduling Algorithm (RR - Round Robin)

Note: User allocated resource

Features: 1) Every user has the same chance to occupy the channel and power. 2) It is very fair for every user, but it is not good to get a best cell throughput.

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PF Scheduling Algorithm(PF- Proportional Fair)Priority for UE = R/r:R: required data rate of UE (calculated TB size per 2ms based on CQI) r: amount of effective data (not including data retransmitted ) transmitted by transport layer for this UE during the past 1.6s The bigger the R/r, the higher the priority (more chance to get resource).Features: 1) A good balance scheme, whose fairness and resource allocation efficiency is between RR and max C/I scheduling algorithm. 2) Probability of serving all users is the same, although different users have different average channel quality. 3) This scheme accounts for balance between system throughout and fairness.

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HSDPA Key Techniques

Fast Scheduling(2ms short frame and scheduling) AMC (support QPSK and 16QAM) HARQ

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Adaptive Modulation and Coding (AMC)AMC could improve radio bandwidth and fit for high speed radio transmission. AMC is based on channel qualityAdjust data rateGood channel condition higher rate Poor channel condition lower rate

Adjust code rateGood channel condition higher rate (e.g. 3/4 code) Poor channel condition lower rate (e.g. 2/4 code)

Adjust modulation schemeGood channel condition 16QAM Poor channel condition QPSK

Channel Quality Feedback (CQI)UE measures channel quality (SNR) and reports to Node B every 2ms or longer time. Node-B chooses modulation scheme, Transport Block size and data rate based on CQI. Throughput ~ SIR Relationship

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Modulation SchemeHSDPA ModulationQPSK 16QAM

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CQI Mapping Table (Category 10)CQI value 0 1 2 3 4 5 6 7 12 13 14 15 16 ... 21 22 23 24 25 26 30 Transport Block Size N/A 137 173 233 317 377 461 650 1742 2279 2583 3319 3565 ... 6554 7168 9719 11418 14411 17237 25558 1 1 1 1 1 1 2 3 4 4 5 5 ... 5 5 7 8 10 12 15 QPSK QPSK QPSK QPSK QPSK QPSK QPSK QPSK QPSK QPSK QPSK 16-QAM 16-QAM 16-QAM 16-QAM 16-QAM 16-QAM 16-QAM 16-QAM Number of HS-PDSCH Modulation Reference power adjustment Out of range 0 0 0 0 0 0 0 0 0 0 28800 0 0 0 0 0 0 0 0 0 0 0 NIR XRV

AMC and modulation scheme recommend in protocol Node-B chooses modulation scheme, transport block size and data rate based on CQI.HUAWEI TECHNOLOGIES CO., LTD. Huawei ConfidentialPage 18

Link Emulation- AMCAMC PerformanceTU5(Fixed MCS) TU30(Fixed MCS) TU120(Fixed MCS)600 500 AMC gain

TU5(AMC) TU30(AMC) TU120(AMC)

AMC changes transmission parameters depending on channel condition and optimize data rate. AMC performance is affected by channel quality error and feedback delay in fading channel. For low data rate, AMC has better performance than fixed MCS. For high data rate, AMC has worse performance than fixed MCS.

Throughput(kbps)

400 300 200 100 0 -12

-11

-10

-9

-8

-7

-6

-5

-4

-3

HS-DSCH Ec/N0(dB)

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AMC Processing Flow

UE measure CPICH strength UE reports the signal quality by CQI (channel quality indicator) Node B may filter and rectify CQI report to obtain actual CQI Determine the channel number, transmit power and modulation scheme, etc, based on CQI, transmit data volume, available power and code.

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HSDPA Key Techniques

Fast Scheduling(2ms short frame and scheduling) AMC (support QPSK and 16QAM) HARQ

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Hybrid Automatic Repeat Request (HARQ)HARQ helps minimize retransmission time and increase cell throughout. Tranditional ARQdecode received transport block detect if there is CRC error in decoded transport bolck If there is CRC error discard error block Request retransmission

Hybrid ARQdecode received transport block Detect if there is CRC error in decoded transport bolck If there is CRC error Store error block(no discard) Request retransmission Combine the currently received retranmission with the previous failed decodes.

Combined HARQBlock1 Block1 Block2

Soft Combine

Block1

Block1 Block1?

Increment redundancy

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HARQ ConceptHARQ is a technique that transmitter sends new set of check bits if the previous transmission failed (NACK) while receiver buffers the failed decodes for soft combining with future retransmissions. The RV parameter indicates different code bit transmit in IR buffer. Different RV parameter configuration supports:CC (Chase Combining): retransmit th