5-A-1 GSM-To-UMTS Training Series 21_HSDPA Principles_V1_0

7/30/2019 5-A-1 GSM-To-UMTS Training Series 21_HSDPA Principles_V1_0

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HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

HUAWEI Confidential

Internal

Principles of HSDPA

GSM-to-UMTS Training Series V1.0

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Change History

Zhang Bibo

lThe GPRS coding scheme is

added in P5.

lComparison of the HARQ and

IR is added in P26.

lBasic concepts are added in

the footnotes of P4, 20, 21, 26,

27, 37, and 44.

1.12009-01-08

Gao BoInitial draft1.02008-12-20

AuthorDescriptionRevision versionDate

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Objectives

[ Similarities and Differences Between

HSDPA and GPRS

[ Basic Concepts and Features of HSDPA

[ Key Technologies of HSDPA

[ Physical Channels of HSDPA

[ Data Transmission and Flow Control of

HSDPA

l In this course, you will learn:

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Contents

Chapter 1 HSDPA vs GPRS

Chapter 2 Basic Concepts and Features of HSDPA

Chapter 3 Key Technologies of HSDPA

Chapter 4 Physical Channels of HSDPA

Chapter 5 Data Transmission and Flow Control of HSDPA



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HSDPA vs GPRS&EGPRS

Multiple access

technology:

TDMA+CDMA

Multiple access

technology:

FDMA+TDMA

AMC: Adaptive

modulation and

coding

MCS1 to MCS9CS1 to CS4 coding

Modulation:

16QAM, QPSK

Modulation:

GMSK, 8PSK

Physical channel:

HS-DSCHPhysical channel:

PDTCH

Scheduling: Channel

condition, delay,

fairness

Scheduling:

User priority

HSDPA GPRS&EGPRS

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Contents








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HSDPA Basic Concepts

HSDPA = High Speed Downlink Packet Access

An Important Feature of the 3GPP R5



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HSDPA Features

HSDPA is a WCDMA solution offering higher speed downlink data services.

l Peak data rate in DL: 14.4 Mbit/s

l Shorter delay

l Higher downlink code and power efficiency and larger downlink capacity

l Flexible cell resource allocation

l More high speed user access



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Overview of HSDPA Key Technologies

AMC Fast SchedulingHARQ (Hybrid ARQ)

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



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HSDPA Key Technologies

Fast scheduling (2 ms subframe and

scheduling)

AMC (supporting QPSK and 16QAM)

HARQ



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Fast Scheduling Basic

If a little part of the 10 ms frame (15 timeslots) cannot be decoded

properly, the whole frame is retransmitted 10 ms later.

If a 2 ms subframe (3 timeslots) cannot be decoded properly, only

this 2 ms subframe is retransmitted. The HARQ process of other 2

ms subframes (a maximum of 6) can continue transmitting data.This greatly improves the resource usage on the air interface.



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Fast Scheduling

lScheduler can be based on

lCDM, TDM

[ Channel condition

[ Amount of data in the queue (delay)

[ Fairness

[ Cell throughput

Scheduling principle:

Based on channel conditions

in short terms;

Based on the throughput and

fairness for users in long terms.

l Basic schedulers

[ Round Robin (RR)

[ Max-C/I

[ Proportional Fair (PF)

All codes towhich

HSDPAtransmission

is mapped

(5inthis example)

Data to UE#1 Data toUE#2 Data to UE#3 CodeCode

Time

Fast scheduling enables effective allocation of available cell and code resources and improves the cell throughput.



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Share and Scheduling of the Shared Channel

Scheduling with four users

CDM+TDM

Scheduling with four users

CDM+TDM

All codes

reserved for

HSDPA

transmissio

n2ms



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Users to transmit

data

Power

Channel code

Data attributes

Fast Scheduling Process

Scheduling Algorithm

Available resources

Required resources

Middle statistics

Input of the scheduling algorithm:

1. Available resources, including power and channel code resources

2. Required resources, including users, data, retransmission, capability evaluation of

the air interface, channel power, uplink and downlink compression gap of the channel,

and discard timer.

3. Middle statistics of the scheduling algorithm, such as the waiting time and average C/I.

Output of the scheduling algorithm:

User to transmit data, power, channel code, data attributes (including queue ID, Xrv,

invalid data packet discarded)

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Max C/I Scheduling Algorithm

Features:

1. The max C/I scheduling algorithm allocates resources to the user with the max C/I in

one TTI.

2. This scheme provides the maximum cell throughput, because the users provided

with services are in best channel conditions.

3. The scheme, however, fails to guarantee fairness for users. In fact, users on the cell

edge receive large penalty and great impact because of too much service delay and

signal quality deterioration.



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RR Scheduling Algorithm

Features:

1) The RR scheduling algorithm adopts the "First in First Allocated" principle for users.

2) The users have high fairness at the cost of high system overhead and high expenseof system throughput (spectral efficiency ).



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Fast Scheduling (2 ms subframe and

scheduling)

AMC (Supporting QPSK and 16QAM)

HARQ



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CQI Mapping Table (Category 10)

016-QAM152555830

0

016-QAM121723726

016-QAM101441125

016-QAM81141824

016-QAM7971923

016-QAM5716822

016-QAM5655421

.........

016-QAM5356516

0QPSK5331915

0QPSK4258314

0QPSK4227913

0QPSK3174212

0QPSK26507

0QPSK14616

0QPSK13775

0QPSK13174

0QPSK12333

0QPSK11732

0288000QPSK11371

Out of rangeN/A0

XRVNIRReference power adjustment DModulationNumber of

HS-PDSCH

Transport Block SizeCQI value

AMC scheme recommended by the protocol

Adopt corresponding TB size, modulation mode,and TX power based on the CQI



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Link Emulation - AMC

AMC (AMC (Adaptive modulation and channel codingAdaptive modulation and channel coding)) PerformancePerformance

The AMC modifies the TX

parameters based on the

instantaneous channel

condition and optimizes the

data rate.

The AMC performance is

affected by channel quality

strategy error and feedback

delay in channel fading.

For low data rate, the AMC

has better performance thanthe fixed MCS.

For high data rate, the

AMC has worse

performance than the fixed

MCS

AMC gai n

0

100

200

300

400

500

600

- 12 - 11 - 10 -9 - 8 - 7 - 6 - 5 - 4 - 3

HS-DSCH Ec/N0(dB)

Throughput(kbps)

TU5(Fi xed MCS) TU5(AMC)

TU30(Fi xed MCS) TU30( AMC)

TU120(Fi xed MCS) TU120(AMC)



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AMC Process

The UE measures the RX channel.

The UE provides the CQI.

The NodeB filters and corrects the reported CQI to obtain the actual CQI

(Channel Quality Indicator).

Configure the number of channels, TX power, modulation mode based on the

CQI, amount of data to be transmitted, and available power and code resources.



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Fast Scheduling (2 ms short frame and scheduling)

AMC (supporting QPSK and 16 QAM)

HARQ



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Hybrid Automatic Repeat Request (HARQ)

Traditional ARQ

Decode received transport blocks

Check for the CRC errors in the decoded

transport blocks

Errors exist

Discard the block with errors

Request retransmission

Hybrid ARQ

Decode received transport blocks

Check for the CRC errors in the decoded transport

blocks

Errors exist

Store instead of discard the block with errors

Request retransmission

Combine the newly received retransmission

block with the previous blocks

Combined processing

Increment redundancy

HARQ helps reduce retransmission time and increase cell throughput.



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HARQ Concept

HSDPA is a technique where the transmitter sends the new set of

parity bits if the previous transmission fails (NACK) and receiverbuffers the failed decodes for soft combing with future

retransmissions.

The RV parameter indicates different code bits transmit in IR buffer.

Different RV parameter configurations support:

Chase Combining (CC) (retransmission of the same coded data)

PIRPartial Incremental Redundancy (PIR) (systematic bitstransmission first)

Full Incremental Redundancy (FIR) ( parity bits transmission first)

Use different r parameters and set of puncture bits for different

retransmission. This ensures average coded bits transmission.



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HARQ Gain

One retransmission gain for different retransmission scheme

8.44.33.53.1FIR Gain (dB)

6.53.63.33.1PIR Gain (dB)

3.03.03.03.0CC Gain (dB)

3/42/31/21/3Code Rate

The IR scheme, which preferentially transmits parity bits,

has average effective codes bits after retransmission. The

HARQ gain is prominent especially in high coded rate.



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Link Emulation - HARQ

HARQ Performance

HARQ reduces the impactHARQ reduces the impact

by channel measurementby channel measurement

errors and feedback delayerrors and feedback delay

and provides the AMCand provides the AMC

performance gain.performance gain.

Higher Speed, higherHigher Speed, higher

HARQ gainHARQ gain

HARQ Gai n 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. 5HS-DSCH Ec/N0(dB)

Throughput(kbps

)

TU5(AMC+HARQ) TU5(AMC)

TU30(AMC+HARQ) TU30( AMC)

TU120(AMC+HARQ) TU120(AMC)



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Link Emulation CC and IR

The HARQThe HARQ--based IR provides the performance gain.based IR provides the performance gain.

Static Channel

0.1

1

Ec/Ior

BLER

First Transmission CC Full IR Partial IR

PA3

0. 1

1

Ec/I or

BLER

Fi rst Transmi ssi on CC Ful l I R Parti al I R



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HSDPA Physical Channel MappingT ra ns po r t C ha nne l s

D C H

R A C H

C P C H

B C H

F A C H

P C H

P hy s i ca l C ha nne l s

D ed i ca ted Ph y s i ca l D a t a Ch an n e l (D PD CH )

D ed i ca ted P h y s ica l Co n t ro l Ch an n e l (D P CC H )Ph y s ica l Ran d o m A cces s Ch an n e l (PRA CH )

Ph y s ica l Co m m o n Pack e t Ch an n e l (PCP CH )

Co m m o n P i l o t Ch an n e l (CPICH )

Pr i m ary Co m m o n Co n t ro l Ph y s ica l Ch an n e l (P -C C P C H )

Seco n d a ry Co m m o n Co n t ro l Ph y s ica l Ch an n e l (S -C C P C H )

Synchroni sa t ion Channel (SCH)

Acq uis it ion Ind ica t o r C hannel (A ICH )

Access Pream ble A cqu i s it ion Ind ica tor C hannel (A P - AIC H)

Paging Ind ica to r Ch an n e l (P ICH )

CPC H S t a tu s In d ica to r Ch an n e l (CSICH )

Col l i s ion - D etec t ion /Channel - Ass ig nment Ind ica tor

Ch an n e l (CD /CA -IC H )

D S C H Ph y s ica l D o w n l i nk Sh a red C h an n e l (PD SCH )

H S-D S CH -re la t ed Sh a red Co n t ro l Ch an n e l (H S-SCC H )

H S-D SCH H i g h Sp eed Ph y s ica l D o w n l in k Sh a red Ch an n e l (H S-PD SCH )

D ed i ca t ed Ph y s ica l Co n t ro l Ch an n e l (u p li n k ) fo r H S -D SCH (H S-D PC CH )



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Associated Channel DPCH

Besides the 3 physical

channels, there is anther

dedicated channel DPCH,

which is called associated

channel in the HSDPA. The

DPCH is used for signaling

transmission and power

control.

The DPCH normally does

not carry services, but it can

carry real-time services

such as the AMR (multipleRABs: CS+PS)



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HSDPA Physical Channel

HS-SCCH and HS-PDSCH are

both downlink shared channelsshared by all user. How can

users know when and on which

channel the users data is

transmitted?

HS-SCCH is like a soldier holding the flag at the

first row of the queue. The UE continuously

monitors the HS-PDSCH subframes addressed to it

on the sets of the HS-PDSCHs. Upon receiving an

HS-PDSCH frame for the UE, the UE physical layerdemodulates the subframe. Otherwise, no

response is performed.



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Physical Channel Timing

Align the HS-SCCH with the P-CCPCH. The HS-PDSCH has two slots difference with the HS-

SCCH. The UE demodulates the HS-PDSCH according to the HS-SCCH.

The HS-SCCH and PDSCH are both common channels. Therefore, there is no timing between

the HS-SCCH/PDSCH and the DPCH.

HS-SCCH

HS-PDSCH

3 slots = 2 ms

DPCH

DPCH

Radio 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

Radio 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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Physical Channel Slot Format (3): HS-DPCCH

Features of the uplink HS-DPCCCH

2 ms TTI (3 slots), SF=256, rate: 15 kbit/s, bearing 2 types of HSDPA uplink physical layer signaling,

including the ACK/NACK and CQI

ACK and NACK notify the NodeB of the UE has received correct downlink data. Definition of the field:

1-Nack, 0-Ack

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

reported periodically. The period ranges from 0 to 160 ms. 0 means no transmission. Normally the

period is 2 ms (every TTI).

ACK/NACK and CQI have different functions and therefore can be controlled independently by

different parameters.

ACK/NACK/CQI can be configured with the number of repeat transmission (max: 4) to improve the

TSTD gain.

S u b f r a m e # 0 S u b f r a m e # i S u b f r a m e # 4

H A R Q - A C K C Q I

O n e r a d i o f r a m e T f = 1 0 m s

O n e H S - D P C C H s u b fr a m e ( 2 m s )

2 T s l o t = 5 1 2 0 c h i p sT s l o t = 2 5 6 0 c h i p s



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Transmit Power of the HSDPA Physical Channels

PHSDPA (HSDPA total transmit power) PHS-PDSCH+PHS-SCCHThe HS-PDSCH transmit power can be adjusted by the NodeB

according to the following factors:CQI

Amount of transmitted data

Available power allocated to the HS-PDSCH

Available codes allocated to the HS-PDSCH

The transmit power of the HS-SCCH can use:

Fixed power transmission (outdoor: 5%; indoor: 3%)

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

channel. The transmit power of the HS-PDSCH is usually greater

than that of the associated channel to ensure that the associated

channel keeps a proper transmit power.

The HS-DPCCH transmit power has a power offset based on the UL

DPCH.The slot bearing the HARQ-ACK/NACK and that bearing the CQI can

have different power offsets.



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HSDPA Channel Mapping (1)

When RAB is mapped to the HS-DSCH, the DCH is required to be

configured to transport UL RLC ACK information and possible UL data,

regardless of whether there is UL data to be transported.

The figure in the next page describes the scenario of DL TRB carried onthe HS-DSCH and SRB and UL services on the DCH. In soft handovers,

there may be one or more DCHs, but there is only one HS-DSCH.


HSDPA Ch l M i (2)


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HSDPA Channel Mapping (2)



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Flow Control for a Single User


Flow Control for Iub Interface


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Flow Control for Iub Interface


HSDPA Data Transmission and Flow Control


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HSDPA Data Transmission and Flow Control

HSDPA flow control is implemented in the MAC-hs. The MAC-hs has fourfunctional entities: flow control, scheduling/priority handling, HARQ, and TFRI.

Flow control is used to control data flow from MAC-d or MAC-c/sh to satisfy air

interface capability and reduce delay and congestion. Flow control of the data

stream from MAC-d with individual priority is independent.

Position of flow control in the MAC-hs entity

Position of flow control in

the MAC-hs entity

Flow control

Scheduling/Priority

handling

Resource allocation

&HARQ

TFRC



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Documents

5-A-1 GSM-To-UMTS Training Series 21_HSDPA Principles_V1_0