HSDPA Basic Principle Ver 2 Revise

7/31/2019 HSDPA Basic Principle Ver 2 Revise

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Technology Explorer Department 1

HSDPA

Basic Principle

By Parames F.Technology ExplorerDepartment


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HSDPAo HSDPA is a key new feature in 3GPP Rel.5

o Ithas been designed to increase Downlinkpacket data throughput by fast physical layer

retransmission and transmission combining aswell as fast link adaptation controlled byNodeB.

o Best-effort packet data which peak rate at14.4 Mbps


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HSDPA Vs WCDMA Rel.99HSDPA

o Shared Channel

o 14.4 Mbps peakthroughput

o 16QAM/QPSK

o Code Combination

o Layer 1 with F-HARQ (at

NodeB)o 2 ms TTIo Adaptive Modulation and

Coding (AMC)

Rel.99

o Dedicated Channelo 384 kbps peak user

throughput

o QPSK

o Single Code per DCH

o RLC Layer with ARQ (at

RNC)o 10 - 80 ms TTI

o Variable SF and FastPower Control (1500 Hz)


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Coexisting and complementary wireless access technologiesfor different use cases

Degree of mobility

Stationary

Walking

Driving

User data rate802.16a,d

802.16e

(IEEE 802.11x)

(802.20)

Full mobility

Fully embedded in 3G mobile network

Data turbo HSDPA / HSUPA for a mobile

DSL feeling

First standardized WiMAX solution

Limited mobility

Fixed mobile substitution

First all-IP solution for

450 MHz available now

High speed wide area data services

Fixed mobile substitution


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Agendao HSDPA compare to WCDMA R99

o Key Technologies

o Resource Managemento Mobility Management


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Key Technology for HSDPAo Share Channel Transmission: Trunking gain from using a

shared channel for multiple users (dynamic resourceassignment)

o Fast Scheduling: Fast scheduling in time (2 ms) and code

(15 parallel codes) reduces the latency and improvespeak rate

o AMC (Adaptive Modulation and Coding): AdaptiveModulation and Coding lead to higher data rates and

optimize spectral efficiency ~ Higher user/cellthroughput

o HARQ (Hybrid Automatic Repeat Request): Hybrid ARQleads to higher efficiency in transmission & error

correction


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Shared Channel Transmissiono Efficient code utilization

SF=1

SF=2

SF=4

SF=8

SF=16

Channelization codes allocatedfor HS-DSCH transmission

8 codes (example)

TTI

Sharedchannelization

codes

User # 1 User # 2 User # 3 User # 4



Fast SchedulingDedicated scheduling mechanism is located in the NodeB

(MAC-hs Scheduler) and used to determine:

o Which UEs shall be served in a transmission time interval (TTI)

o Basic idea: transmit at fading peaks

o May lead to large variations in data rate between users

o Tradeoff: fairness vs cell throughput

User 1

User 2

ScheduledUser

High data rate

Low data rate

Time

User 1 User 2 User 2 User 2User 1User 1


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Fast Scheduling

Maximum C/I

Round Robin

Proportional Fairness

Throughput

Fairness

Good

GoodBad

Bad



AMC: Adaptive Modulation and CodingIn HSDPA, the modulation and coding rate can be quickly and

flexibly determined by NodeB for each 2 ms TTI, base on theradio condition report from UE

HSDPA NodeB

Low Quality Radio Environment High Quality Radio Environment

ModulationCoding RateThroughput

QPSK(2bit/symbol) 16QAM(4bit/symbol)R=1/6

(High error correction) R=8/9(Low error correction)14.4 Mbps(15 Codes)480 kbps(1 Code)



AMC: Adaptive Modulation and CodingIn HSDPA, power control and variable SF are disable and

replaced by AMC

HSDPA AMC

o Good Radio Condition High data rate

o Poor Radio Condition Low data rate

Rel. 99 Power Control

o Good Radio Condition Low transmit power

o Poor Radio Condition High transmit power


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Fast Hybrid Automatic Repeat Request (HARQ)o HARQ is located in the NodeB and provides lower delay

than existing ARQ mechanism (RLC Acknowledge Modelocated in the RNC).

P1,1 P1,2 P2,1 P2,2 P2,3

P1,1 P1,2 P2,1 P2,2 P2,3

Transmitter

Receiver

NA

CK

ACK

NA

CK

NA

CK

ACK

Conventional ARQ (discard erroneous transmission)

P1,1 P1,2 P2,1 P2,2 P3,1

P1,1 P1,1 P2,1 P2,1 P3,1

Transmitter

Receiver

NACK A

CK

NACK A

CK

ACK

Hybrid ARQ (store erroneous and soft combine)

P1,2 P2,2


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Fast Hybrid Automatic Repeat Request (HARQ)There are two aspect for HARQ

o Chase combining

o The HARQ retransmits the same data packet

o The UE decodes the prior received erroneous

data packet with the retransmitted packet

o Incremental Redundancy

o The HARQ retransmits additional differentredundant information

o The UE decodes the prior received erroneousdata packet with additional redundant information

o Higher performance but need more memory,suitable for low data rate


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Fast Hybrid Automatic Repeat Request (HARQ)o Multiple HARQ processes allows continuous transmission to a

single usero Example: 6 HARQ processes, 5 ms UE processing 2.8 ms

NodeB processing

P1,1 P2,1 P3,1 P4,1 P5,1Transmitter

Receiver

P6,1

P1,1 P2,1 P3,1 P4,1 P6,1P5,1

Processing time (fixed, 5 ms)

NACK

P1,1

P1,2 P7,1 P3,2 P8,1

P1,2

P7,1

P3,2

P8,1P3,1

Chase combining by L1 in UE

Proc #1Proc #2Proc #3

Proc #4Proc #5

Proc #6

Processing time (fixed, 2.8 ms)


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o Key Technologies



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New HSDPA Physical Channelso HS-PDSCH: High Speed Physical Downlink Shared Channel

o Downlink Channel for HSDPA data transmission

o QPSK or 16 QAM

o HS-SCCH: High Speed Shared Control Channel

o Downlink Channel for the signaling related to HS-PDSCH:(UE Id, Channelization code info, Modulation scheme, HARQ info, etc.)

o HS-DPCCH: High Speed Dedicated Physical Control Channel

o Uplink Channel for feed back signaling related to HS-PDSCH:(ACK/NACK, CQI-Channel Quality Indicator)

o A-DPCH: Associated Dedicated Physical Channel

o Rel. 99 DPCHUL: Rel. 99 signaling, TCP ACK/NACK, Data transmissionDL: Rel. 99 signaling, Voice/VDO-multi RAB


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New HSDPA Physical ChannelsHS-PDSCH

(DL data transmission: SF=16)

HS-SCCH(for DL Signaling: SF=128)

HS-DPCCH(for ACK/NACK and CQI: SF=256)

A-PDCH

HSDPA NodeB

HSDPA UE


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Dynamic Resource Allocationo RNC dynamically allocates channelization codes for HSDPA

according to the instantaneous traffic mix betweenWCDMA and HSDPA

o NodeB dynamically allocates power for HSDPA according tothe instantaneous traffic mix between WCDMA and HSDPA

CarrierTransmissionpower

Max NodeB power

HSDPA power

Non HSDPA power

Time


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Code Multiplexingo Allow sending data to many users in parallel within the same

TTIo One HS-SCCH for one user in each TTI

o Maximum number of user in each TTI is 4 (UE capability)

2 ms

User # 1

User # 2

User # 3

User # 4

Control data

User data

HS-SCCHs

HS-DSCH


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HS-SCCHo Part 1 (1 slot) contain a time critical parameter

o This information is needed to start the demodulationprocess.

o Scrambled with UE ID.

o Part 2 (2 slots) contain less time-critical parameter

Part 1 (Channelization code set, modulation scheme)R=1/3 convolutional coded, scrambled with UE ID

Part 2 (transport block size, HARQ parameters, UE-specific CRC)R=1/3 convolutional coded

HS-SCCH(SF= 128)

3 slots (1 TTI)


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HS-DPCCHo Uplink signaling for ACK/NACK and CQI (Channel Quality

Indicator)o Time relative to downlink HS-PDSCH

ACK/NACK

Available processing time 5 ms (7.5 slots)

HS-DPCCH(SF= 256)

CQI

HS-DSCH

1 slot 2 slots


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CQI (Channel Quality Indicator)o Channel quality is estimated by CQI which is provide by UE

on HS-DPCCHo UE decides CQI value in order to keep BLER of received

signal under desired target value

o UE transmit the CQI value on HS-DPCCH

o NodeB selects modulation scheme (QPSK/16QAM), numberof HS-DPSCH (115) base on CQI mapping table, UEcapability and power left in that cell


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CQI (Channel Quality Indicator)Example of CQI table

CQIvalue

TransportBlock Size

Numberof

HS-PDSCH

Modulation

Referencepower

adjustment

NIR XRV

0 N/A Out of range

1 137 1 QPSK 0 960

0

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

8 792 2 QPSK 0

9 931 2 QPSK 0

29 7168 5 16-QAM -7

30 7168 5 16-QAM -8

Table 7A: CQI mapping table for UE categories 1 to 6.


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HSDPA and Rel.99 physical channel mappingOVSF Code allocation in

o 15 codes are allocated for HS-DPSCH

PCPICHPCCPCHAICHPICH

SCCPCH

HS-SCCHA-DCHA-DCHA-DCHA-DCHA-DCHA-DCH

SF=16 SF=32 SF=64 SF=128 SF=256

0

1

15

HS-PDSCH

HS-PDSCH

Utili ti f d t


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Utilization of code tree


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o Key Technologies



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HSDPA MobilityRequired Process for HSDPA mobility

o Channel Type Switching (HS-DSCH DCH)

o Base on traffic volume and network HSDPA capability

o SHO for A-DCH

o During SHO, the best active set with HSDPA availablewill be the HSDPA serving cell

NodeB1 NodeB2

Active set

A-DCHHS-DSCH


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HSDPA MobilityServing HS-DSCH cell change

o HS-DSCH is established on the best cell

o With UE moving, the Report Event 1a, 1b, 1c or 1d would be reportto SRNC

o If the best cell change and the new best cell still HSDPA cell,

HS-DSCH cell Change will be performed toward new best cell

A-DCHHS-DSCH

NodeB1 NodeB2

Active set

HS-DSCH state

NodeB1 NodeB2

Active set

HS-DSCH state


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HSDPA MobilityInward Mobility (DCH -> HS-DSCH)

o DCH is established on the best cell

o With UE enter into HSDPA cell, the Report Event 1a, 1b or 1cwould be report to SRNC

o If the HSDPA become the best cell, Channel Type Switching

(DCH -> HS-DSCH) is performed and then HS-DSCH is establishon the best cell

NodeB1 NodeB2

Active setA-DCHHS-DSCH

CTSDCH state

NodeB1 NodeB2

Active set

HS-DSCH state


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HSDPA MobilityOutward Mobility (HS-DSCH -> DCH)

o HS-DSCH is established on the best cell

o With UE move out of HSDPA cell to non HSDPA cell, the ReportEvent 1a, 1b ,1c or 1d would be report to SRNC

o If the non HSDPA become the best cell, Channel Type Switching

(HS-DSCH -> DCH) is performed and then DCH is establish on thebest cell, non HSDPA cell

A-DCHHS-DSCH

NodeB1 NodeB2

Active set

HS-DSCH state

NodeB1 NodeB2

Active set

DCH stateCTS


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HSDPA MobilityInter Frequency/Inter System Mobility

o CTS from HS-DSCH to DCH will be performed in order to beready for IFHO/ISHO by R99 mechanism

o Some vendors plan to implement Compressed Mode for HSDPAfeature. It could be new better IF/IS mobility mechanism???

A-DCHHS-DSCH

CTS

NodeB1 NodeB2

Active set

HS-DSCH state

NodeB1 NodeB2Active set

DCH state

NodeB1 NodeB2

Active set

DCH state

HHO

NodeB1 NodeB2Active set

HS-DSCH stateF1F2


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Thank You

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HSDPA Basic Principle Ver 2 Revise