Aida Botonjić Tieto 1 WCDMA/HSPA Aida Botonjić
Aida Botonjić Tieto 1
WCDMA/HSPA Aida Botonjić
Aida Botonjić Tieto 2
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
Aida Botonjić Tieto 3
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
Aida Botonjić Tieto 4
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
Aida Botonjić Tieto 5
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
Aida Botonjić Tieto 7
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
Aida Botonjić Tieto 9
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
Aida Botonjić Tieto 10
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)
Aida Botonjić Tieto 12
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
Aida Botonjić Tieto 14
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)
Aida Botonjić Tieto 17
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