00-wcdma hsdpa principles[1]
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Gii thiu HSDPA
ISSUE 1.0
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Contents
1.1. Khi nim v HSDPAKhi 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
2.2. HSDPA Key TechniquesHSDPA Key Techniques
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HSDPA Key Techniques
AMC (AdaptiveModulation & Coding)
Data rateadaptedto radio conditionon 2ms
Fast Scheduling basedonCQI and fairness
Schedulingofuseron 2ms
HARQHybridautomatic repeat
request with Soft combing
Reduce roundtriptime
16QAM
16QAMin complementto QPSKfor higherpeak bit rates
SF16, 2ms and CDM/TDM
Dynamic sharedinTimeand codedomain
3New 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 condition channel 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 every2ms or more cycle
NodeB selects modulation scheme ,data block size based on CQI
Bad channel condition
MorepowerNode B Node B
Power Control RateAdaptation
Good channel condition
Bad channel condition
Good channel condition less power
lowdata rate
high data rate
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CQI mapping table for UE category 10
CQIvalueCQIvalueTransportTransport
Block SizeBlock Size
Number ofNumber of
HSHS--PDSCHPDSCHModulationModulation
Reference powerReference power
adjustmentadjustment((
00 N/AN/A Outof rangeOutof range
11 137137 11 QPSKQPSK 00
22 173173 11 QPSKQPSK 00
1313 22792279 44 QPSKQPSK 00
1414 25832583 44 QPSKQPSK 00
1515 33193319 55 QPSKQPSK 00
1616 35653565 55 1616--QAMQAM 00
1717 41894189 55 1616--QAMQAM 00
1818 46644664 55 1616--QAMQAM 00
2828 2337023370 1515 1616--QAMQAM 00
2929 2422224222 1515 1616--QAMQAM 00
3030 2555825558 1515 1616--QAMQAM 00
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HSDPA UE Categories
UE Category MaximumNumberof HS-
DSCH CodesReceived
Minimum Inter-TTI Interval
Maximum Numberof Bits ofanHS-DSCH Transport Block
Received Withinan HS-DSCHTTI
TotalNumberof SoftChannel 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 thereceiver
In case of Chase combining ( CC ) each retransmission is an
identical copy of the original transmission
In case of Incremental Redundancy ( IR ) each retransmissionmay 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 sharedchannel 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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Shared Channel Transmission
The codes are assigned to HSDPA user only when they are
actually to be used for transmission, which leads to efficient
code and power utilization
Allchannelization
codes availablefor HSDPA
Time
Channelizationcode
data 2 data data
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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 anddecode
SRNC(MAC-d)
power monitor
CQI adjustment
Scheduler
Queues/flowcontrol
HARQ
TFRC
Power
management
Codingandmodulation
OMparameters
Power limitation
Power for HSDPA
CQI Value
Stat. Of ACK/NACK
ACK/NACKWaiting time
Queue filling infoQueue priority
CQI ValueCodeallocation
Code available
Data flow
Control signal
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