Owa324010 Wcdma Hsdpa Ran12 Principles Issue1.00

8/13/2019 Owa324010 Wcdma Hsdpa Ran12 Principles Issue1.00

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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA HSDPA

Principles


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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved. Page2

References

3GPP Release 6 Specification References TS 25.308 HSDPA overall description stage2

TS 25.211 Physical channel and mapping of transport channels onto physical

channel (FDD)

TS 25.212 Multiplexing and channel coding (FDD)

TS 25.213 Spreading and modulation (FDD)

TS 25.214 Physical layer procedure (FDD)

TS 25.306 UE radio access capabilities

TS 25.321 Medium Access Control (MAC) protocol specification

TS 25.322 Radio Link Control (RLC) protocol specification

TS 25.331 Radio Resource Control (RRC) protocol specification


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Objectives

Upon completion of this course, you will be able to:

Define HSDPA protocol stack

Describe new channels for HSDPA

Explain the physical channel processing

HSDPA impact on protocol stack

Identify HSDPA UE categories

Define HSDPA protocols of Mac sub-layer


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Contents

1. HSDPA Introduction

2. HSDPA Key Techniques

3. HSDPA Physical Layer Channel

4. HSDPA Layer2 Protocol


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WCDMA Evolution

Downlink Peak Data Rate

(Typical Deployment)

Downlink Peak Data Rate

(Theoretical Maximum)

GSM 9.6kbps 9.6kbps

GPRS 40kbps 171kbps

EDGE 120kbps 473kbps

R99 WCDMA 384kbps 2.0Mbps

HSDPA 10.0Mbps 14.4Mbps

GSM GPRS

EDGE

WCDMA

R99

HSDPA

R5

HSUPA

R6


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High Speed Downlink Packet Access

What are the benefits of HSDPA

Higher Data Rates

Peak data rate up to 14Mbps per user

Higher Capacity More subscribers and throughput

Further reduces the cost per megabyte

Richer Application

Low latencyimprovement for streaming ,interactive, background

applications


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Release 99 Packet Data

How is Packet Data handled in Release 99 (FDD) ?

DCH ( Dedicated Channel )

Spreading codes assigned per user

Closed loop power control

Soft handover

FACH ( Common Channel )

Common Spreading code

No closed loop power control

No soft handover

Node B

Node B


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Release 99 Downlink Limitation

Dedicated Channel Features ( DCH )

Maximum implemented downlink of 384kbps

OVSF code limitation for high data rate users

Rate change 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


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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

2ms

HSDPA user#1

HSDPA user#2

HSDPA user#3

HSDPA user#4

Node B

a set of HS-PDSCHs

Code multiplexing for HSDPA

2ms

Big shared pipe


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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 )


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Comparison Summary

Mode DCH FACH HSDPA

Channel Type Dedicated Shared Shared

Power Control Closed Inner Loopat 1500Hz &Closed Outer Loop

No Fixed Power withlink adaptation

Soft Handover Supported Not Supported Not Supported

Suitability for

BurstyPoor Good Good

Data Rate Medium Low High


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Contents



3. HSDPA Physical Layer Channels



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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 ARQwithSoft 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?

+


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Adaptive Modulation and Coding

AMC ( Adaptive Modulation and Coding ) in accordancewith CQI ( Channel Quality Indicator )

Adjust data rate to compensation channel condition

Good channel conditionhigher data rate

Bad channel conditionlower data rate

Adjust channel coding rate to compensation channel condition

Good channel conditionchannel 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 conditionhigh order modulation scheme e.g. 16QAM

Bad channel conditionlow order modulation scheme e.g. QPSK


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Adaptive Modulation and Coding

AMC ( Adaptive Modulation and Coding ) based on CQI

( Channel Quality Indicator )

CQI ( channel quality indicator )

UE measures the channel quality and reports to NodeB every2ms or more cycle

NodeB selects modulation scheme ,data block size based on CQI

Bad channel condition More power

Node B Node B

Power Control Rate Adaptation

Good channel condition

Bad channel condition

Good channel conditionless power

low data rate

high data rate


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CQI mapping table for UE category 10

CQI valueTransport

Block Size

Number of

HS-PDSCHModulation

Reference power

adjustment

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


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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

HSDPA RF performance depends on UE capability


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Hybrid Automatic Repeat reQuest

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 ( HARQ )

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 applied

to the combined signal


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Hybrid Automatic Repeat reQuest

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


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HARQ Combining

There are many different schemes for HARQ with soft

combining

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


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HARQ Process

Each HSDPA assignment is handled by a HARQ process

runing in NodeB and UE

The UE HARQ process is responsible for:

Attempting to decode the data

Deciding whether to send ACK or NACK

Soft combining of retransmitted data

The NodeB HARQ process is responsible for:

Selecting the corrected bits to send according to the selectedretransmission scheme and UE capability


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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


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Shared Channel Transmission

In HSDPA, a new DL transport channel is introduced call

HS-DSCH

A part of the total downlink code resource is dynamically

shared between HSDPA and Release 99


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Power Sharing for Channel Transmission

A part of the total downlink power resource is dynamically

shared between HSDPA and Release 99

Time

Allowed power for HSDPA

Total Power

DPCH

Power for CCH

Higher power utility

efficiency

TimePower margin for DCH power control


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Resource Allocation

Resources are assigned to HSDPA user only when they are

actually to be used for transmission, which leads to efficient

code and power utilization


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Higher-Order Modulation Scheme

HSDPA modulation scheme

QPSK

16QAM


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Fast Scheduling

Fast scheduling is about to decided to which terminal the

shared channel transmission should be directed at any

given moment

Scheduler may be based on: CDM, TDM

Channel condition

Amount of data waiting in the queue

Fairness (Satisfied users)

Cell throughput, etc

Some basic scheduler Round Robin (RR)

Maximum C/I (MAX C/I)

Proportional Fair (PF)

Enhanced Proportional Fair

(EPF)


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HSDPA New Physical Channels


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Contents






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R99 Channel Mapping


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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 Physical Control Channel

High Speed Physical Downlink Shared Channel ( HS-PDSCH )

Downlink Physical Channel

High Speed Dedicated Physical Control Channel ( HS-DPCCH )

Uplink Physical Control Channel


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R5 Channel Mapping


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Physical Layer Frame Duration

Frame Duration

10ms radio frame, 15 slots

2ms HSDPA sub-frame, 3 slots

1 HS-DSCH Transport Time interval (TTI)

Slot Duration

2560chips per slot

7680 chips per HSDPA sub-frame

Symbol Timing

QPSK: 2bits / symbol

16QAM: 4bits / symbol

R99 radio frame

10ms

HSDPA sub-frame

2ms

Time slot

0.67ms


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HS-PDSCH Sub-frame Structure

HS-PDSCH sub-frame structure

3 time slots constituted one TTI (2ms) , only one TB will be sent

during one TTI

Fixed spreading factor ( SF=16 )

May use QPSK or 16QAM modulation scheme

Up to 15 HS-PDSCH may be assigned simultaneously

All HS-PDSCH used to carry users data

UE can be assigned multiple OVSF code ( SF=16 ) based on UE

Categories


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HS-SCCH Sub-frame Structure

HS-SCCH subframe structure 3 time slots constitutes one TTI ( 2ms )

SF=128, QPSK only, Fixed rate of 60kbps

HS-SCCH carries the following control messages: Xue, Xccs, Xms,

Xrv, Xtbs, Xhap and Xnd

UE demodulates HS-SCCH sub-frame and find out the received dataaddressed to the UE with Xue. Then UE demodulates HS-PDSCH

sub-frame with Xccs, Xms, Xrv, Xhap, Xtbs and Xnd are used for

HARQ Process

UE may need to simultaneous monitor up to four HS-SCCHs


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HS-DPCCH Sub-frame Structure

HS-DPCCH sub-frame structure TTI=2ms ( 3 time slots ), SF=256, Fixed rate of 15kbps

Carry 2 types of HSDPA uplink physical layer control message,

including ACK/NACK CQI


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Uplink HS-DPCCH Preamble and

Postamble

Transmit Preamble and Postamble on HS-DPCCH around

ACK / NACK

Eases the decoding, which allows HS-DPCCH to operate at

lower power


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Associated Physical ChannelA-

DPCH

Besides 3 physical channels on top. There is another

physical channel named DPCH, which is a dedicated

channel . DPCH is also called associated channel used for

signalling transmission and power control

DPCH does not carry service generally, sometimes carry

real time (RT) service such as AMR service


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Fractional Dedicated Physical Channel

(F-DPCH)

The F-DPCH is a new physical channel in Release 6

Purpose of F-DPCH introduction is to keep the closed loop

power control working for HSDPA users without an

assigned DPCH (A-DPCH)


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F-DPCH Frame Structure

The F-DPCH carries control information generated at layer 1 (TPCcommands). It is a special case of downlink DPCCH

Each frame of length 10ms is split into 15 slots, each of length

Tslot = 2560 chips, corresponding to one power-control period,

SF=256

Each user occupy one Symbol in one slot to bear TPC command,

Pilot and TFCI is not needed

Up to 10 users can be multiplexed on one F-DPCH(Tx OFF)NOFF2bits

Slot #0 Slot #1 Slot #i Slot #14

Tslot= 2560 chips

1 radio frame: Tf= 10 ms

TPC

NTPCbits

(Tx OFF)

NOFF1bits


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HSDPA Physical Channels Timing

Start of HS-SCCH is aligned with the start of PCCPCH

HS-PDSCH, subframe is transmitted two slots after the

associated HS-SCCH subframe

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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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


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More Data Rate Factors

More factors that affect HSDPA data rate Inter- TTI interval

Retransmission

ACK / NACK Repetition

Assuming

5 OVSF code for HS-PDSCH

Consecutive assignment

QPSK

Turbo code rate =1/3

Retransmission

75% of data block decoded on first transmission

25% of data block decoded on second transmission


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Contents






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UMTS Protocol Stack


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HSDPA Protocol Stack


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MAC Architecture


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UTRAN MAC-hs Architecture


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UTRAN MAC-hs Functions

Flow Control

The flow control entity controls the HSDPA data flow between

RNC and NodeB

Purpose: to reduce the transmission time of HSDPA data on

the UTRAN side and to reduce the data discarded and

retransmitted when the Iub interface or Uu interface is

congested

The transmission capabilities of the Uu interface and Iub

interface are taken into account in a dynamic manner in the

flow control


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Scheduling

The scheduling entity handles the priority of the queues and

schedules the priority queues or NACK HARQ processes of the

HS-DSCH UEs in a cell to be transmitted on the HS-DSCH

related physical channels in each TTI

Purpose: to achieve considerable cell throughput capability and

to satisfy user experience


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HARQ

The HARQ entity handles the HARQ protocol for each HS-

DSCH UE

Each HS-DSCH UE has one HARQ entity on the MAC-hs of

the UTRAN side to handle the HARQ functionality

One HARQ entity can support multiple instances (i.e.HARQ

processes) of stop and wait HARQ protocols

Based on the status reports from HS-DPCCH, a new

transmission or retransmission is determined


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TFRC selection

The TFRC selection entity selects an appropriate transport

format and resource for the data to be transmitted on HS-

DSCH

The transport format includes the transport block size and

modulation scheme. The resource includes the power resource

and code resource of HS-PDSCH

Transport Format and Resource Combination (TFRC) for each

UE is channel quality based, where AMC is the key technique


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UE MAC-hs Functions


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Summary






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Owa324010 Wcdma Hsdpa Ran12 Principles Issue1.00

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