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WCDMA/HSPA Aida Botonjić

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1990 2000

1st generation

Analogue speech

NMT, AMPS, TACS

2nd generation

Digital speech + low-rate data (<64 kbps)

GSM, PDC, IS-95,

IS-136 (D-AMPS)

Multimedia services(<2 Mbps)

+ 2nd gen. services

3rd generation

UMTS/IMT-2000

1980

Background

LTE

2010

Faster Multimedia services

(30-100Mpbs)+ 3rd gen. services

4th generation

LTE

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3GPP releases

R99: WCDMA Evolved R5: HSDPA – High Speed Downlink Packet Access R6: HSUPA – Enhanced Uplink

LTE – Long-Term Evolution

Enhanced Uplink (HSUPA)

MIMOCPC

Enhanced Downlink(HSDPA)

Rel 4 Rel 5 Rel 6

HSPAHSPAWCDMAWCDMA

R99 Rel 7 Rel 8

HSPA EvolutionHSPA Evolution

LTELTE

= Third Generation Partnership Project

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Why WCDMA/HSPA?

• Applications:• E-mail• Video telephony• Web browsing• Content sharing, e.g. Picture/video upload.

• Devices (UE):• Broadband modem• Mobile phones with

• Large color screen• Gbyte memories

• HSPA Targets:• Adapt to fast variations in radio conditions• Reduced delays• Improved High-Bitrate Availability• Improved Capacity

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WCDMA network architecture

Node B

Node B

RNC RNC

dedicated channels

Iur

Iub

Iu

Core network(Internet, PSTN)

UE

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Frame structure

#0 #1 #2 #3 #14

One slot, 2/3ms

One radio frame, 10 ms

#13

One subframe, 2ms

Time slot is the shortest repetitive period

Radio frame is the shortest transmission duration

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HSDPA Basic Principles

Shared Channel TransmissionDynamically shared in time & code

domain

Higher-order Modulation16QAM in complement to QPSK for

higher peak bit rates

2 ms

Short TTI (2 ms)Reduced latency

Fast Hybrid ARQ with Soft Combining

Reduced round trip delay

Fast Radio Channel Dependent Scheduling

Scheduling of users on 2 ms time basis

Fast Link AdaptationData rate adapted to radio

conditions on 2 ms time basis

t

P

Dynamic Power AllocationEfficient power &

spectrum utilisation

= HS-DSCH

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HSUPA Basic Principles

Fast Retransmissions Roundtrip time ~2 ms possible Soft combination of multiple attempts

Fast Radio-Dependent Scheduling 2 ms time basis

2 ms

Short TTI (2 ms) Reduced latency

= E-DCH

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Shared Channel Transmission

A set of radio resources dynamically shared among multiple users, in time and code domain Efficient code utilization

Efficient power utilization

Channelization codes allocatedfor HS-DSCH transmission

8 codes (example)SF=16

SF=8

SF=4

SF=2

SF=1

TTI

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

Shared channelization

codes

time

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Fast Channel-dependent Scheduling

Scheduling = which UE to transmit to at a given time instant and at what rate

Basic idea: transmit at fading peaks May lead to large variations in data rate between users Tradeoff: fairness vs cell throughput

high data rate

low data rate

Time#2#1 #2 #2#1 #1 #1

Scheduled user

User 1

User 2

TTI

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Fast Link Adaptation

Adjust transmission parameters to match instantaneous channel conditions

HS-DSCH: Rate control (constant power) Adaptive coding Adaptive modulation (QPSK or 16QAM) Adapt on 2 ms TTI basis fast

Release 99: Power control (constant rate)

Good channelconditions

less power

Bad channelconditions

more power

power control (HSUPA E-DCH)

Good channelconditions

high data rate

Bad channelconditions

low data rate

rate adaptation (HSDPA HS-DSCH)

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Higher Order Modulation

16QAM may be used as a complement to QPSK 16QAM allows for twice the peak data rate compared to QPSK

16QAM

2 bits/symbol 4 bits/symbol

QPSK

Release 99: only QPSK

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Short 2 ms TTI

Reduced air-interface delay Improved end-user performance

Necessary to benefit from other HS-DSCH features Fast Link Adaptation Fast hybrid ARQ with soft combining Fast Channel-dependent Scheduling

10 ms20 ms40 ms80 ms

Earlier releases

2 msRel 5

2 ms

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ACK

TO RNC

TransmitterReceiver

Rapid retransmissions of erroneous data• Hybrid ARQ protocol terminated in Node B short RTT (typical example: 2 ms)• Soft combining in UE of multiple transmission attempts reduced error rates for retransmissions

Fast Hybrid ARQ with Soft Combining

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NACK

TO RNC

ACK

TransmitterReceiver

Fast Hybrid ARQ with Soft Combining

Rapid retransmissions of erroneous data• Hybrid ARQ protocol terminated in Node B short RTT (typical example: 2 ms)• Soft combining in UE of multiple transmission attempts reduced error rates for retransmissions

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Dynamic Power allocation

Dedicated channels (power controlled)

Common channels

Power usage with dedicated channels channels

t

Unused power

Power

To

tal

ce

ll p

ow

er

3GPP Release 99 3GPP Release 5

t

P

Downlink channel with dynamic power allocationt

To

tal

ce

ll p

ow

er

Power

Dedicated channels (power controlled)

Common channels

HS-DSCH (rate controlled)

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Conclusion

Rel 99 HSPA (Rel 5 & 6)

Channel transmission in time domain

Channel transmission in time and space domain

Scheduling Channel dependent scheduling

QPSK modulation QPSK and 16 QAM modulation

TTImin= 10ms TTImin= 2ms

ARQ HARQ

Static power allocation Dynamic power allocation

- Link adaptation