u lii 106 hsdpa basic principle 20081202 a 1.0

8/6/2019 U LII 106 HSDPA Basic Principle 20081202 a 1.0

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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

Security Level: Internal Use Only

www.huawei.com

HSDPA Basic Principle


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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 1

Learning Objectives

HSDPA basic principle and feature

HSDPA key technologies

HSDPA physical channels


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Contents

Chapter 1 HSDPA Basic

Concepts and Characteristics

Section 2 Key Techniques

Section 3 Physical Channel


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HSDPA Basic Concepts

HSDPA = 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 Characteristics

HSDPA is the solution of WCDMA offering higherspeed 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 access

HSDPA


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Contents



Chapter 2 Key Techniques

Chapter 3 Physical Channel


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HSDPA Key Techniques- OverviewHSDPA Key Techniques- Overview

AMC F

ast Sch

edulingH

ARQ (H

ybrid ARQ)

16QAMSF16, 2ms and CDM/TDM 3 New Physical Channels

Adaptive Modulation and Coding Hybrid Automatic Repeat Request


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HSDPA Key Techniques

Fast Scheduling(2ms short frame

and scheduling)

AMC (support QPSK and 16QAM)

HARQ


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Fast Scheduling Basic

If 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.

Physical Layer Basic


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Fast SchedulingFast Scheduling

Scheduling Principle: based on channelcondition in short period; based on balancebetween throughout and proportional fairfor allusers in long period.

Some basic scheduler

Round Robin (RR)

Maximum C/I (MAXC/I)

Proportional Fair (PF)

By fast scheduling, HSDPA cell can allocate the available HSDPA power resource and

code resource among users effectively, to improves the throughout.

Scheduler may works based on CDM

and/or TDM

Channel condition Amount of data waiting in the queue (delay)

Fairness

Cell throughout, etc


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Share and Scheduling of Shared Channel

The following fig describes scheduling processing for 4 users.

All codesreserved forHSDPAtransmission

2ms


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Fast Scheduling ProcessFast Scheduling Process

Transmit powerforwhich users

Channelization code

Data attributes

Scheduling Algorithm

Available resource

Required resource

Temporary statistic

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 powerforwhich users, power, channelization code, data attributes


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Max C/I Scheduling AlgorithmMax 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 fairfor 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)RR Scheduling Algorithm (RR - Round Robin)

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.

Note: User allocatedresource


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PF Scheduling AlgorithmPF Scheduling Algorithm

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.

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 toget resource).

(PF- Proportional Fair)


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Fast Scheduling(2ms short frame and

scheduling)

AM

C(supp

ort QPSK and 16QAM)

HARQ


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Adaptive Modulation and Coding (AMC)Adaptive Modulation and Coding (AMC)

AMC is based on channel quality

Adjust data rate

Good channel condition higher rate

Poor channel condition lower rate

Adjust code rate

Good channel condition higher rate (e.g. 3/4 code)

Poor channel condition lower rate (e.g. 2/4 code)

Adjust modulation scheme

Good channel condition 16QAM

Poor channel condition QPSK

Channel Quality Feedback (CQI)

UE measures channel quality (SNR) and reports toNode B every 2ms or longer time.

Node-B chooses modulation scheme, Transport Block

size and data rate based on CQI.

Throughput ~ SIR Relationship

AMC could improve radio bandwidth and fit for high speed radio transmission.


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HSDPA Modulation QPSK

16QAM

Modulation SchemeModulation Scheme


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CQI Mapping Table (Category 10)CQI value

Transport Block

SizeNumberofHS-PDSCH Modulation Reference power adjustment ( NIR XRV

0 N/A Out of range

1 137 1 QPSK 0

28800 0

2 173 1 QPSK 0

3 233 1 QPSK 0

4 317 1 QPSK 0

5 377 1 QPSK 0

6 461 1 QPSK 0

7 650 2 QPSK 0

12 1742 3 QPSK 0

13 2279 4 QPSK 0

14 2583 4 QPSK 0

15 3319 5 QPSK 0

16 3565 5 16-QAM 0

... ... ...

21 6554 5 16-QAM 0

22 7168 5 16-QAM 0

23 9719 7 16-QAM 0

24 11418 8 16-QAM 0

25 14411 10 16-QAM 0

26 17237 12 16-QAM 0

0

30 25558 15 16-QAM 0

AMC and modulation scheme recommend in protocol

Node-B chooses modulation scheme, transport block size and data rate based on CQI.


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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 modulationscheme, etc, based on CQI, transmit data volume, available power

and code.


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Fast Scheduling(2ms short frame and

scheduling)

AMC (support QPSK and 16QAM) HARQ


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HARQ Concept

HARQ is a technique that transmitter sends new set of check bits ifthe 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 the same coded data

PIR (Partial Incremental Redundancy): transmit systematic bits first

FIR (Full Incremental Redundancy): transmit parity bits first


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HARQ Gain

One retransmission gain for different retransmission scheme

Code Rate 1/3 1/2 2/3 3/4

CC Gain (dB) 3.0 3.0 3.0 3.0

PIR Gain (dB) 3.1 3.3 3.6 6.5

FIR Gain (dB) 3.1 3.5 4.3 8.4

FIR scheme will transmit the check bits first, it has effective average

coded bits after retransmission. Especially for high code rate, the

HARQ gain is very evidence.


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Link Emulation- HARQ

HARQ( Hybrid ARQ) Performance

HARQ may reduce effect by

channel measure error and

feedback delay, and provide AMC

performance gain.

Higher speed, higher HARQ gain.

HARQ Gain over AMC

0

100

200

300

400

500

600

-12.5 -11.5 -10.5 -9.5 -8.5 -7.5 -6.5 -5.5 -4.5 -3.5

HS-DSCH Ec/N0(dB)

Throughput(kbps)

TU5(AMC+HARQ) TU5(AMC)




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Contents



Section 2 Key Techniques

Section 3 Physical Channel


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HSDPA Relevant Physical Channel

Three new HSDPA Physical Channel

For each HS-DPCCH, SF=256

Each H has one HS-DPCCH.

For each HS-SCCH, SF=128

Each cell is assigned up to 4 HS-

SCCH (limited by UE capability)

For each HS-PDSCH, SF=16


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HSDPA Channel Mapping


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HSDPAPhysi l Channel (HS-SCCH)

HS-SCCHand HS-PDSCH

are downlink sharedhannel shared byall users.

How an users knowwhen

and onwhi h hannel my

data is transported?

HS-SCCH is like soldiers holding

flags at the first row of queue. UE

keeps on monitoring the HS-SCCH

channels to identify any HS-PDSCH

subframes addressed to it on the sets

ofHS-PDSCH channels. Up

onreceiving an HS-PDSCH subframe for

the UE, the UE physical layer will

demodulates the subframe, otherwise

do nothing.


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Physical Channel Slot Format (HS-PDSCH)

Slot #0 Slot#1 Slot #2

Tslot= 2560 chips, M*10*2kbits (k=4)

Data

Ndata1bits

1 subframe: T f= 2 ms

HS-PDSCH Slot Format Attributes:

3 slots in one TTI (2ms)

Fixed spreading factor SF16

QPSK or 16QAM modulation

Only carry user data

UE may be assigned multi channelization codes to support multi-code transport

depending on UE capability.


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Physical Channel Slot Format (HS-DPCCH) Uplink HS-DPCCH

TTI 2ms (3 slots), SF 256, Fixed rate of 15Kbps,carry 2 types of HSDPA uplink physical layer

signaling: ACK/NACK and CQI. ACK and NACK notifies the NodeB if UE has received correct downlink data or not. The field

defines like this:1-Nack, 0-Ack

CQI is a metric that reflects physical channel quality indicator based on CPICH, and reported

by period ranging from 0, 2ms. to 160ms (0 means no transmission). Usually the period is

2ms (one TTI).

ACK/NAK and CQI having different function may be controlled independently by different

parameters . ACK/NACK/CQI could be configured to repeat up to 4 times to improve TSTD gain.

ra e ra e ra e

ARQ-A K QI

One ra i ra e s

One - s ra e ( s)

v sl t c i ssl t c i s


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Physical Channel Timing Start of HS-SCCH is aligned with the start of P-CCPCH, HS-PDSCH subframe

is transmitted two slots after the associated HS-SCCH subframe. UE

demodulates HS-PDSCH subframe according to HS-SCCH. HS-SCCH and PDSCH are common channels, so there are not timing between

HS-SCCH/PDSCH and DPCH.

HS-SCCH

HS-PDSCH

3 slots = 2 ms

DPCH

XDPCH

adio frame with (SFN modulo 2) = 0P-CCPCH

2 slots

3 slots = 2 ms

Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot

15 slots = 10 ms

Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4

adio frame with (SFN modulo 2)=1

10 ms

Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4

HS-DPCCH

3 slots = 2 ms

~7.5 slots


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UE Capacity Category( for reference)


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HSDPA Physical Channel Transmit Power PHSDPA(HSDPA total transmit power) PHS-PDSCH+ PHS-SCCH

The HS-PDSCH transmit power is adjusted by Node B according

to the following factors:

CQI

Amount of data to be transmitted

Available power for HS-PDSCH

Available code resource for HS-PDSCH

HS-SCCH transmit power may use:

Fixed power transmission (outdoor 5%, indoor 3% of the total power)

A fixed power offset between HS-SCCH and DL associated channel

(PDCH). HS-PDSCH transmit power is usually bigger than the PDCH

channel to keep a proper transmit power.

HS-DPCCH transmit powerhas a poweroffset based on UL DPCH.

Slot carrying HARQ-ACK/NACK or CQI may be set different power offset.


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HSDPA Channel MappingWhen RAB is mapped onto HS-DSCH,

DPCH is needed to transport UL RLC

AM information and possible UL data, nomatter there is UL data to transport.

The following figure describes that DLTRB is carried on HS-DSCH SRB and

SRB or UL service is carried on DCH. In

soft handover, there may be one or more

DCH, but only one HS-DSCH.


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u lii 106 hsdpa basic principle 20081202 a 1.0

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