1 Harmonization Meeting on 3GPP HSDPA and 3GPP2 1xEV-DV Work New-Jersey 13-14 Nov 2001 HSDPA...

1

Harmonization Meeting on 3GPP HSDPA and 3GPP2 1xEV-DV Work New-Jersey 13-14 Nov 2001

HSDPA presentation

3GPP TSG RAN WG2 Chairman, Nortel Networks

3GPP TSG RAN WG1 Chairman, Nokia

HSDPA rapporteur, Motorola

2


• Introduction• Overall architecture and principles• Radio interface aspects• Physical layer aspects• Future activities

Content

3



Content

4


HSDPA objectives

• Increased packet data support– Increase maximum user throughput for downlink packet data (streaming,

interactive and background services)– Lower packet delay

• Compatibility– Evolutionary philosophy – HSDPA architecture is a straightforward enhancement to the R99

architecture • addition of a repetition entity at the Node B below release 99 MAC

layer– All R99 techniques can also be supported in a network supporting HSDPA– Mobiles with HSDPA capability can co-exist with R99 mobiles on the

same carrier

• Standardisation of all interfaces– Including Iur/Iub interfaces

5


HSDPA operation

Node B is enhanced to handle:

• HARQ Retransmissions

• Modulation/coding selection

• Packet data scheduling

Data packets

Data packet

+ possible retransmissions

ACK/NACK

+ TPC commands

+ feedback

Node BRNC

HSDPA capable UE

6


HSDPA Performance• Study in year 2000 (Release 4) indicated a

doubling of capacity compared to Rel'99– Dependant on assumptions, such as scheduler

and cell isolation

7



Content

8


Key additions to R99

• Adaptive Modulation • Hybrid ARQ• Scheduling/repetition at Node B• Shorter radio frame

9


Release 99 DSCH architecture

L2

L1

DSCH

FP

RLC

L2

L1

L2

L1

L2

L1

DSCH

FP

Iub Iur

PHY

MAC

PHY

RLC

Uu

DSCH

FP

DSCH

FP

MAC-c/sh

MAC-D

UE Node B DRNC SRNC

10


Release 5 HS-DSCH Architecture

L2

L1

HS- DSCH

FP

RLC

L2

L1

L2

L1

L2

L1

HS-DSCH

FP

Iub Iur

PHY

MAC

PHY

RLC

Uu

MAC HS-

DSCH

HS- DSCH

FP

HS-DSCH

FP

MAC-c/sh

MAC-D

Optional Entities

UE Node B DRNC SRNC

11


HSDPA in UTRAN architecture

• HSDPA introduction– Compatible with all transport options (AAL2

and IP)– Minor impact on network architecture

• No Impact on RLC• New RRC parameters• No impact on mobility• UTRAN functional hierarchy still valid

12


MAC-HS

• New MAC-HS entity in the Node B– Two sub-entities – one for scheduling and one for HARQ– Permits fast, adaptive scheduling to leverage AMC and

HARQ techniques, thus enabling higher peak data rates– Includes common scheduling/priority handling function

as in R99 MAC-c/sh– Provides HARQ functionality– HARQ round trip optimized to keep soft memory

requirements at UE to a minimum– Reduces delay for successful decoding of packet

compared to RNC based architecture

13


HS-DSCH Transport Channel

• Similar attributes as R99 DSCH, with the following modifications– Shorter fixed TTI value (frame size) of 2 ms– One transport block (data block) per TTI– Fixed length CRC (24 bits) per data block– Dynamic modulation– Rate 1/3 Turbo coding

• Effective code rate achieved with rate matching• Dynamic redundancy version

14



Content

15


UTRAN MAC Architecture

HS-DSCH HS-DSCH

Associated Uplink Signalling

Associated Downlink Signalling

FACH RACH

DCCH DTCH DTCH

DSCH

MAC Control

Iur or local

MAC Control

DCH DCH

MAC-d

USCH TDD only

MAC-c/sh

CPCH FDD only

CCCH CTCH BCCH SHCCH TDD only

PCCH

FACH PCH USCH TDD only

DSCH Iub

MAC Control

MAC-hs

Configuration B

Configuration A

Configuration A

16


MAC-HS-DSCH – UTRAN side

MAC-hs

MAC – Control

HS-DSCH

TFC selection

HS-DSCH

Flow Control MAC-hs / MAC-c/sh or MAC-hs / MAC-d



to MAC-c/sh or MAC-d

HARQ HARQ

Scheduling/Priority Handling

17


MAC-HS-DSCH – UE side

MAC-hs

MAC – Control


To MAC-c/sh


HS-DSCH HS-DSCH

HARQ

Reordering Reordering

18


HARQ Protocol Details

• Asynchronous DL (retransmission can be scheduled independently of occurrence of first transmission)

• Synchronous UL (ACK/NACK timing fixed with respect to downlink transmission)

• Multiple parallel HARQ processes per UE• HARQ processes are common to all HS-DSCH

– Selection of HS-DSCH by HARQ process at first transmission

• Scheduler can abort process at any time• One process can transmit at a time• Multiple priority queues

19


HARQ Protocol cont’d

• Out-of-band (i.e. not on HS-DSCH) signaling supports all HARQ functionality in terms of combining, abort etc.

• In-band (i.e. on HS-DSCH) signaling provides for priority based release of in-sequence PDUs to upper layers at receiver

• In-band signaling provides for re-ordering function at receiver

• Timer based mechanism provides for release of out-of-sequence data blocks– Other mechanisms may be added

20


Physical Layer Functionality

• Transmission of HS-DSCH transport blocks (MAC-hs PDUs)

• DL associated signaling– Scheduling information– HARQ process information– Physical layer information

• UL associated signaling– ACK/NACK– Scheduling assistance indicator

21


DL Signalling

• Two-step approach– Indication of a HS-DSCH transmission provided on

dedicated channel to UE– UE then decodes associated shared control channel– UE finally decodes HS-DSCH

• UE monitors up to four shared control channels• Shared control channels provide information on

transport format and resources for decoding as well as HARQ information (redundancy version, etc.)

• HARQ information and TF information are time-multiplexed to reduce needed processing time

22


DL Physical layer model

PHY

HARQ coding, multiplexing and modulation

HS-DSCH

HARQ info and scheduling info signaling

Phy CH Phy CH Phy CH

PHY

HARQ decoding, de-multiplexing, and demodulation

HS-DSCH

HARQ info and scheduling info signaling

Phy CH Phy CH

Phy CH

UTRAN UE

23


UL Physical Channel Model

PHY

decoding, de-multiplexing,and demodulation

HS-DSCH

HARQ feedback and schedulingassistance information

Phy CHPhy CH

DCH

PHY

coding, multiplexing, andmodulation

HS-DSCH

HARQ feedback and schedulingassistance information

Phy CHPhy CH

DCH

UTRAN UE

24


Hybrid ARQ with HSDPA

• Fast Hybrid ARQ (Retransmission controlled at Node B ->) Less round trip delay

• Combining of the retransmission and first transmission at UE– Node B terminated ARQ protocol means reasonable

terminal memory requirements– Both identical (Chase combining) and non-identical

(Incremental redundancy) retransmissions allowed• terminal memory capability definition based on the

identical retransmissions -> maximum data rate assumes identical retransmissions, lower rates possible also with non-identical retransmissions (Incremental Redundancy)

25


HSDPA Operation Principle

2 ms

ACK/NACK

DataData

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

DataData

DataData

DataData

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

DataData

DataData

DataData

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

PilotPilot

TFCITFCI

TPCTPC

DataData

DataData

Uplink DCH

Downlink DCH

PilotData Data PilotData Data PilotData Data PilotData Data PilotData Data PilotData Data PilotData Data PilotData Data PilotData Data

HS-SCCH

HS-DSCH

Demodulation Control

Note: Timing from data to ACK/NACK under discussion!

ACK/NACK after data decoding

26


HSDPA Operation

• Several users can be code multiplexed together • This allows better granularity than with time

multiplexing only and takes terminal capability into account (all terminals are not going to be 10.8 Mcps terminals!)

• Node B has information of the transmission power for each terminal (Power control commands from the terminal) + ACK/NACK feedback info in the uplink

• The number of codes used for HSDPA can vary dynamically between 1 and 15, terminals expected to have varying code handling capability as in Rel'99/Rel'4.

27



Content

28


DL Physical Layer

• HS-PDSCH – fixed spreading factor = 16 (all channelization codes with same scrambling code)

• HS-DSCH has frame length (TTI) of 2 ms (3 slots)– Note this is valid for FDD only– For TDD slightly different principles are used with TTI

definition

• HS-SCCH – shared control channel – SF=128 or 256 (under study)

• UE can be assigned multiple physical channels based on its capability

• Code division multiplexing of UEs within one TTI is allowed

• QPSK and 16-QAM allowed

29


DL Channel Timing

• Associated dedicated channel carrying allocation indication on one slot– Insertion of an indicator by puncturing the data part

(DPDCH) of the physical channel• Shared control channel and Physical shared data channel

have a one slot overlap (HS-PDSCH codes to receive + modulation indication in the first timeslot)

• Transport Format (time critical) and CRC+HARQ information time multiplexed to reduce needed processing time

– HARQ information and TF information are time-multiplexed (The channelisation codes & modulation to be used delivered on the control channel before the data part transmission starts)

• Target round trip of 12 ms

30


UE DL operation

– Maximum 4 HS-DSCH Shared Control Channels that a single UE is monitoring

• Network can configure 1 to 4 to UE (more can be used at cell level)

• Good performance assuming reasonable terminal complexity.

– With continuous activity terminal is able to listen only one control channel.

– The terminal memory requirement shall be derived based on Chase (soft) combining i.e. at max data rate (as given by terminal capability) only Chase combining can be used.

• Network partitions UE memory to various HARQ processes

31


UL Physical Layer for UL signaling

• New Physical channel SF=256 code multiplexed with current dedicated uplink physical channels

• ACK/NACK and Feedback time multiplexed– 1 slot ACK/NACK (or DTX)

• synchronous to DL HS-DSCH timing

– 2 slots either DTX or explicit feedback• Indication of downlink transmissions compatible with

target BLER

Channel Codern bits 20 coded bits

over 2 slots

10 bits/slot

Repeat1 bit 10 bits

On one slot

32


Physical layer timing

Shared control channel, split in 2 parts

HS-DSCH

TTI = 3slots

T DL_control=5slots

HI

Spreading codes, modulation

Parameters

FHARQ parameters, CRC etc...

AssociatedDPCH

Unsynchronisedtiming of UEs:within 1 slot

33


Modulation Aspects

• Both QPSK (as in Rel'99) and 16QAM are defined

• All terminals with HSDPA capability shall support also 16QAM.

• 8PSK & 64QAM were agreed not to be part of HSDPA Rel'5

1011 1001 0001 0011

1010 1000 0000 0010

111 0 11 00 0100 011 0

1111 11 01 0101 0111

i2 i2

i1

q 1

q 2

q 2

0 .3 1 6 2 0 .9 4 8 7

0.31

620.

9487

34


Channel coding

• Rel'99 rate 1/3 Turbo coding is used, other effective coding rates e.g. 1/4, are created with rate matching

• Hybrid ARQ repetitions do not have to be identical in Layer 1, i.e. Incremental Redundancy (IR) can be used

• Channel coding chain is simplified due:

– Only one TrCh per TTI– Only 1 interleaving step– No radio frame segmentation

needed– No DTX during the TTI

TrBlk concatenation

CRC attachment

Code block segmentation

Channel Coding

Rate matching /Incremental Redundancy blk

Physical channelsegmentation

Interleaving

Physical channel mapping

PhCH#1 PhCH#2

35


HSDPA Data Rates (Peak)

• Modulation method QPSK, 16QAM and potentially also 64 QAM– Currently 64 QAM not in Release 5– 10.8 Mbps achievable with 15 codes and 16QAM.

• Coding rates 1/4-3/4 (Rel'99 Turbo Encoder + rate matching)• Spreading factor 16 used in above table

Chip Rate = 3.84 McpsFrame Size = 3 slots

Modulation 10 codes Turbo coding rateInfo Rate(Mbps)

Info bits perframe

64QAM 10.8000 21600 3/416QAM 7.2000 14400 3/416QAM 4.8000 9600 1/2QPSK 2.4000 4800 1/2QPSK 1.2000 2400 1/4

36


UE Capability

• The following parameters characterize a HSDPA terminal capability:

• Maximum number of Transport channel bits per HS-DSCH TTI

• Maximum number of soft channel bits over all HARQ processes

• Number of channelization codes (or, equivalently, number of channel modulation symbols per TTI)

• Minimum inter-TTI interval (to be considered when defining lower capability UE classes)

– Allowed combinations to be defined so as to reduce number of cases

– QPSK and 16 QAM are mandatory for HSDPA capable terminals

37


• Introduction• Overall architecture and principles• Radio interface aspects• Physical layer aspects• Future enhancements

Content

38


Examples of future items

• More modulations• MIMO• Multiple simultaneous receptions in

terminal• New associated DPCH structure

39


Evolution

• HSDPA is part of UTRAN release 5, and will be improved along with the other UTRAN features

40


Back-up slides

41


Adaptive Modulation

• Higher order modulation provides higher peak data rates in favorable channel conditions.

• Gives the flexibility to match Modulation Coding Scheme to the average channel conditions for each user– Provides coarse data rate selection

• Extends the system’s ability to adapt to good channel conditions beyond the use of SF alone.

• But:– Is sensitive to measurement error and delay. H-ARQ can

enable further adaptation

42


Hybrid-ARQ

• Hybrid ARQ combines initial transmission with repetitions in the physical layer to provide higher decoding probability.

• It automatically adapts to instantaneous channel conditions by adding redundancy only when needed– Insensitive to measurement error and delay– Allows fine data rate adjustment– Independent of various thresholds when combined with

AMC

• Enabled by instantiation of Parallel Hybrid ARQ processes

• Fast uplink feedback channel

43


Scheduling/repetition at Node B

• Scheduling at the Node B lowers the delay for critical channel state information– Needed to exploit Adaptive Modulation and

HARQ to their maximum potential– Scheduler can better adapt modulation and

coding to match current channel conditions and fading environment

– Can exploit multi-user diversity by scheduling users in constructive fades

44


Radio frame size

• Shorter “frame size” reduces payload to manageable level– Provides fast feedback mechanism– Lower delay– Best leverages scheduling on constructive

fades – Benefits primarily for hybrid ARQ– Enables maximum utilization of excess power

for data services (i.e. reduced need for power control margin)

45


Feedback channel in uplink

• Fast feedback channel in uplink pairing the HS-DSCH– Fast status for HARQ re-transmission– Channel condition feedback to MAC-hs for

scheduling

Date post:	19-Jan-2016
Category:	Documents
Upload:	hilary-rosemary-obrien
View:	216 times
Download:	0 times

1 Harmonization Meeting on 3GPP HSDPA and 3GPP2 1xEV-DV Work New-Jersey 13-14 Nov 2001 HSDPA...

Documents