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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.
Gii thiu HSDPAISSUE 1.0
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Contents
1. Khi nim v HSDPA
2. Cc k thut cho HSDPA
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WCDMA Evolution
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Phin bn 99 D liu gi
D liu gi c x l th no trong phin bn 99 (FDD)
DCH ( Knh c gn )
M tri ph c gn cho mi ngi dng
Vng iu khin cng sut kn Chuyn giao mm
FACH ( Knh chung )
M tri ph chung
Khng c vng iu khin cng sut kn
Khng c chuyn giao mm
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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
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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
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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 )
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High Speed Downlink Packet Access (HSDPA)
Comparison Summary
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Contents
1. HSDPA Concepts
2. HSDPA Key Techniques
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HSDPA Key Techniques
AMC (Adaptive Modulation & Coding)
Data rate adapted to radio condition on 2ms
Fast Scheduling based onCQI and fairness
Scheduling of user on 2ms
HARQHybrid automatic repeatrequestwith Soft combing
Reduce round trip time
16QAM
16QAM in complement to QPSKfor higher peak bit rates
SF16, 2ms and CDM/TDM
Dynamic shared in Time and code domain
3 New Physical Channels
Block 1 Block 2Block 1
Block 1?
Block 1Block 1?
+
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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 conditionchannel coding rate is lower 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
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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 powerNode B Node B
Power Control Rate Adaptation
Good channel condition
Bad channel condition
Good channel condition
less power
low data rate
high data rate
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CQI mapping table for UE category 10
CQI value TransportBlock Size
Number ofHS-PDSCH
Modulat ion Reference pow eradjustment
0 N/A Out of range
1 137 1 QPSK 0
2 173 1 QPSK 0
13 2279 4 QPSK 0
14 2583 4 QPSK 0
15 3319 5 QPSK 0
16 3565 5 16-QAM 0
17 4189 5 16-QAM 0
18 4664 5 16-QAM 0
28 23370 15 16-QAM 0
29 24222 15 16-QAM 0
30 25558 15 16-QAM 0
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HSDPA UE Categories
UE 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
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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 appliedto the combined signal.
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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
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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
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Hybrid Automatic Repeat reQuest
( HARQ )
Example for Chase Combining ( CC ) Scheme
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Hybrid Automatic Repeat reQuest
( HARQ )
Example for Incremental Redundancy ( IR ) Scheme
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Fast Scheduling
Fast scheduling is about to decided to which terminal the shared
channel transmission should be directed at any given moment
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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
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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
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Higher-Order Modulation
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HSDPA New Physical Channels
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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
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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
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Implementation of MAC-hs
HS-DPCCHdemodulation and
decode
SRNC(MAC-d)
power monitor
CQI adjustment
Scheduler
Queues/flow
control
HARQ
TFRC
Power
management
Coding
andmodulation
OM
parametersPower limitation
Power for HSDPA
CQI Value
Stat. Of ACK/NACKACK/NACK
Waiting time
Queue filling infoQueue priority
CQI Value
Code
allocationCode available
Data flow
Control signal
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Thank You