11 principles of hsdpa
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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Principles of HSDPA
ISSUE 1.0
Page1Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
� Upon completion of this course, you will be able to:
� Review WCDMA and HSDPA evolution and standards
� Review R99 packet data service method
� Describe HSDPA physical channels
� HSDPA Network and UE protocol stack architecture
Page2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1.1. HSDPA ConceptsHSDPA Concepts
2. HSDPA Key Techniques
3. HSDPA Physical Layer Channels
4. HSDPA Layer2 Protocol
Page3Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Evolution
Page4Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Release 99 Packet Data
� How is Packet Data handled in Release 99 (FDD) ?
� DCH ( Dedicated Channel )
� Spreading codes assigned per user
� Closed loop power control
� Soft handover
� FACH ( Common Channel )
� Common Spreading code
� No closed loop power control
� No soft handover
Page5Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page6Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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 )
Page8Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
High Speed Downlink Packet Access (HSDPA)
� Comparison Summary
Page9Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. HSDPA Concepts
2.2. HSDPA Key TechniquesHSDPA Key Techniques
3. HSDPA Physical Layer Channels
4. HSDPA Layer2 Protocol
Page10Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HSDPA Key Techniques
AMC (Adaptive Modulation & Coding)
Data rate adapted to radio condition on 2ms
Fast Scheduling based on CQI and fairness
Scheduling of user on 2ms
HARQ((((Hybrid ARQ))))with
Soft combing
Reduce round trip time
16QAM
16QAM in complement to QPSK for 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 condition –channel coding rate is higher 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
Page12Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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 power
Node B Node B
Power Control Rate Adaptation
Good channel condition
Bad channel condition
Good channel condition→→→→ less power
→→→→ low data rate
→→→→ high data rate
Page13Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
CQI mapping table for UE category 10
Out of rangeOut of rangeN/AN/A00
001616--QAMQAM151525558255583030
001616--QAMQAM151524222242222929
001616--QAMQAM151523370233702828
……………………………………………………
001616--QAMQAM55466446641818
001616--QAMQAM55418941891717
001616--QAMQAM55356535651616
00QPSKQPSK55331933191515
00QPSKQPSK44258325831414
00QPSKQPSK44227922791313
……………………………………………………
00QPSKQPSK1117317322
00QPSKQPSK1113713711
Reference power Reference power
adjustment adjustment ∆∆∆∆∆∆∆∆ModulationModulation
Number of Number of
HSHS--PDSCHPDSCH
Transport Transport
Block SizeBlock SizeCQI valueCQI value
Page14Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HSDPA UE Categories
28800363015Category 12
14400363025Category 11
17280027952115Category 10
17280020251115Category 9
13440014411110Category 8
11520014411110Category 7
67200729815Category 6
57600729815Category 5
38400729825Category 4
28800729825Category 3
28800729835Category 2
19200729835Category 1
Total Number of Soft Channel Bits
Maximum Number of Bits of an HS-DSCH Transport Block
Received Within an HS-DSCH TTI
Minimum Inter-TTI Interval
Maximum Number of HS-DSCH Codes
Received
UE Category
Page15Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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 applied to the
combined signal.
Page16Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page17Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page18Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page20Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page22Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
� 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
Page23Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Tim e
Channelizationcode
UE1 data UE2 data UE3 data
Page24Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Higher-Order Modulation
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HSDPA New Physical Channels
Page26Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. HSDPA Concepts
2. HSDPA Key Techniques
3.3. HSDPA Physical Layer ChannelsHSDPA Physical Layer Channels
4. HSDPA Layer2 Protocol
Page27Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
R99 Physical Channels
Page28Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page29Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HSDPA Physical Channels
Page30Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HS-PDSCH sub-frame Structure
� HS-PDSCH sub-frame structure
� 3 time slots constituted one TTI (2ms)
� Fixed spreading factor ( SF=16 )
� May use QPSK or 16QAM modulation scheme
� All HS-PDSCH used to carry user’s data
� UE can be assigned multiple OVSF code ( SF=16 ) based on UE Categories
Slot #0 Slot#1 Slot #2
Tslot = 2560 chips, M*10*2 k bits (k=4)
DataNdata 1 bits
1 subframe: T f = 2 ms
Page31Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HS-SCCH sub-frame Structure
� HS-SCCH sub- frame structure
� 3 time slots constitutes one TTI ( 2ms )
� HS-SCCH SF=128, QPSK only
� HS-SCCH carries the following control messages: Xue, Xccs, Xms, Xrv, Xtbs, Xhap
and Xnd
� UE demodulates HS-SCCH sub-frame and find out the received data addressed to
the UE with Xue. Then UE demodulates HS-PDSCH sub-frame with Xccs, Xms, Xrv,
Xhp, Xtbs and Xnd are used for HARQ Process
� UE may need to simultaneous monitor up to four HS-SCCH
Slot #0 Slot#1 Slot #2
T slot = 2560 chips, 40 bits
Data N data 1 bits
1 subframe: T f = 2 ms
Page32Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HS-DPCCH sub-frame Structure
�HS-DPCCH sub-frame structure
� TTI=2ms ( 3 time slots ), SF=256, Fixed rate of 15kbps, carry 2 types of HSDPA uplink
physical layer control message, including ACK/NACK CQI
� ACK and NACK notifies NodeB that UE has received correct downlink data or not. The
field defines like this: 1-NACK, 0-ACK
� CQI reflects physical channel quality indicator based on CPICH strength, and reported
by period range from 0 to 160ms ( 0 means no transmission ). Usually the period is 2ms
( one TTI )
� ACK/NACK and CQI having different function may be controlled independently by
different parameters.
S u b f r a m e # 0 S u b f r a m e # i S u b f r a m e # 4
H A R Q - A C K C Q I
O n e r a d i o f r a m e T f = 1 0 m s
O n e H S - D P C C H s u b f r a m e ( 2 m s )
2 × T s lo t = 5 1 2 0 c h i p s T s lo t = 2 5 6 0 c h i p s
Page33Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Associated physical channel - DPCH
� Besides 3 physical channels on top. There is another physical channel
named DPCH, which is a dedicated channel . DPCH is also called associated
channel used for signalling transmission and power control
� DPCH does not carry service generally, sometimes carry real time (RT)
service such as AMR service
N o d e B
U E
H S -P D S C H H S -S C C H D P C H H S -D P C C H
Page34Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HSDPA Physical Channels Timing
� Start of HS-SCCH is aligned with the start of PCCPCH
� HS-PDSCH, subframe is transmitted two slots after the associated
HS-SCCH subframe
Page35Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page36Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. HSDPA Concepts
2. HSDPA Key Techniques
3. HSDPA Physical Layer Channels
4.4. HSDPA Layer2 ProtocolHSDPA Layer2 Protocol
Page37Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
HSDPA Protocol Stack
Page38Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
UTRAN MAC Architecture
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UTRAN MAC-hs Architecture
Page40Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
UE MAC-hs Architecture
Page41Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Implementation of MAC-hs
HS-DPCCH demodulation and decode
SRNC(MAC-d)
power monitor
CQI adjustment
Scheduler
Queues/flow control
HARQ
TFRC
Power management
Coding and modulation
OM parameters
Power limitation
Power for HSDPA
CQI Value
Stat. Of ACK/NACKACK/NACK
Waiting time
Queue filling info Queue priority
CQI ValueCode allocation
Code available
Data flow
Control signal
Thank YouThank You