principes de l'hsdpa

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Principles of HSDPA

ISSUE 1.0


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

Review WCDMA and HSDPA evolution and standards Review R99 packet data service method Describe HSDPA physical channels HSDPA Network and UE protocol stack architecture


Contents1.1. HSDPA ConceptsHSDPA Concepts

2. HSDPA Key Techniques3. HSDPA Physical Layer Channels4. HSDPA Layer2 Protocol


WCDMA Evolution


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


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


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


High Speed Downlink Packet Access (HSDPA) 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 )


High Speed Downlink Packet Access (HSDPA) Comparison Summary


Contents1. HSDPA Concepts 2.2. HSDPA Key TechniquesHSDPA Key Techniques

3. HSDPA Physical Layer Channels4. HSDPA Layer2 Protocol


HSDPA Key Techniques

AMC (Adaptive Modulation & Coding)Data rate adapted to radio condition on 2ms

Fast Scheduling based on CQI and fairness

Scheduling of user on 2ms

HARQ（ Hybrid ARQ）with Soft combing

Reduce round trip time

16QAM16QAM in complement to QPSK

for higher peak bit rates

SF16, 2ms and CDM/TDMDynamic shared in Time and code domain

3 New Physical Channels

Block 1 Block 2Block 1

Block 1?

Block 1Block 1?

+


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 condition –channel coding rate is higher 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


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 power Node B Node B

Power Control Rate Adaptation

Good channel condition

Bad channel condition

Good channel condition

→ less power

→ low data rate

→ high data rate


CQI mapping table for UE category 10

CQI valueCQI valueTransport Transport Block SizeBlock Size

Number of Number of HS-PDSCHHS-PDSCH

ModulationModulationReference power Reference power

adjustment adjustment

00 N/AN/A Out of rangeOut of range

11 137137 11 QPSKQPSK 00

22 173173 11 QPSKQPSK 00

………… ………… ………… ………… …………

1313 22792279 44 QPSKQPSK 00

1414 25832583 44 QPSKQPSK 00

1515 33193319 55 QPSKQPSK 00

1616 35653565 55 16-QAM16-QAM 00

1717 41894189 55 16-QAM16-QAM 00

1818 46644664 55 16-QAM16-QAM 00

………… ………… ………… ………… …………

2828 2337023370 1515 16-QAM16-QAM 00

2929 2422224222 1515 16-QAM16-QAM 00

3030 2555825558 1515 16-QAM16-QAM 00


HSDPA UE CategoriesUE 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


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 applied to the combined signal.


Hybrid Automatic Repeat reQuest ( 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


Hybrid Automatic Repeat reQuest ( 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


Hybrid Automatic Repeat reQuest ( HARQ ) Example for Chase Combining ( CC ) Scheme


Hybrid Automatic Repeat reQuest ( HARQ ) Example for Incremental Redundancy ( IR ) Scheme


Fast Scheduling Fast scheduling is about to decided to which

terminal the shared channel transmission should be directed at any given moment


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


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


Shared Channel Transmission The codes are assigned to HSDPA user only when they ar

e actually to be used for transmission, which leads to efficient code and power utilizationAll

channelizationcodes available

for HSDPA

Time

Channelizationcode

UE1 data UE2 data UE3 data


Higher-Order Modulation


HSDPA New Physical Channels


Contents1. HSDPA Concepts 2. HSDPA Key Techniques3.3. HSDPA Physical Layer ChannelsHSDPA Physical Layer Channels

4. HSDPA Layer2 Protocol


R99 Physical Channels


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


HSDPA Physical Channels


HS-PDSCH sub-frame Structure HS-PDSCH sub-frame structure

3 time slots constituted one TTI (2ms) Fixed spreading factor ( SF=16 ) May use QPSK or 16QAM modulation scheme All HS-PDSCH used to carry user’s data UE can be assigned multiple OVSF code ( SF=16 ) based on UE

Categories

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, M*10*2 k bits (k=4)

Data N data 1 bits

1 subframe: T f = 2 ms


HS-SCCH sub-frame Structure HS-SCCH subframe structure

3 time slots constitutes one TTI ( 2ms ) HS-SCCH SF=128, QPSK only 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 data addres

sed to the UE with Xue. Then UE demodulates HS-PDSCH sub-frame with Xccs, Xms, Xrv, Xhp, Xtbs and Xnd are used for HARQ Process

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

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, 40 bits

Data N data 1 bits

1 subframe: T f = 2 ms


HS-DPCCH sub-frame StructureHS-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 ACK and NACK notifies NodeB that UE has received correct downlink data or not. The field defines like this: 1-NACK, 0-ACK CQI reflects physical channel quality indicator based on CPICH strength, and reported by period range from 0 to 160ms ( 0 means no transmission ). Usually the period is 2ms ( one TTI ) ACK/NACK and CQI having different function may be controlled independently by different parameters.

Subframe #0 Subframe # i Subframe #4

HARQ-ACK CQI

One radio frame T f = 10 ms

One HS-DPCCH subframe (2 ms)

2 T slot = 5120 chips T slot = 2560 chips


Associated physical channel - 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

Node B

UE

HS-PDSCH HS-SCCH DPCH HS-DPCCH


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


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


Contents1. HSDPA Concepts2. HSDPA Key Techniques3. HSDPA Physical Layer Channels4.4. HSDPA Layer2 ProtocolHSDPA Layer2 Protocol


HSDPA Protocol Stack


UTRAN MAC Architecture


UTRAN MAC-hs Architecture


UE MAC-hs Architecture


Implementation of MAC-hs

HS-DPCCH demodulation and decode

SRNC(MAC-d)

power monitor

CQI adjustment

Scheduler

Queues/flow control

HARQ

TFRC

Power management

Coding and modulation

OM parameters

Power limitation

Power for HSDPA

CQI Value

Stat. Of ACK/NACKACK/NACK

Waiting time

Queue filling info Queue priority

CQI ValueCode allocation

Code available

Data flow

Control signal

Thank You

principes de l'hsdpa

Documents

data block

data applications

itsown data

data transfer

data transmission

required data rate

downlink packet data

higher data rates