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HSDPA Principles

Nov 25, 2014

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The Overview of HSDPA(High Speed Downlink Packet Access)

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 1 Page 1

OutlineIntroduction HSDPA New Techniques Transport and Physical Channels Spreading, Modulation and Coding Protocol Architecture Terminal Capabilities

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 2 Page 2

HSDPA Bit Rate AdvantageTypical average bit rate for different technologies in a medium loaded Macro cell.2000 1800 1600 1400 12001.5 Mbps

kbps 1000800400 kbps

700 kbps

600 400 200 0 GPRSHUAWEI TECHNOLOGIES Co., Ltd.

350 kbps 150 kbps 30 kbps

EDGE

WCDMA

EV-DO

EV-DV

HSDPAPage 3 Page 3

Huawei Confidential

HSDPA Latency AdvantageTypical average round trip time for different technologies. Smaller round trip times would benefit interactive applications.700 600 500 400 300 200 100 0 GPRS/EDGE R99HUAWEI TECHNOLOGIES Co., Ltd.

650 ms

ms

200 ms 100 ms

WCDMA R99Huawei Confidential

HSDPA R5

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HSDPA ConsiderationsThe same carrier can be shared between WCDMA and HSPDA. Its the DL power which should be intelligently divided between two services.Unlike 3GPP2 standards, EV-DO and IS-95/1xRTT, which can not share a carrier.

An evolutionary rather than a revolutionary philosophy. WCDMA networks can be upgraded with HSDPA hardware/software on Node-B by Node-B basis.Even HSDPA features can be added gradually, if required.

Priority to urban environments and indoor deployments. Support full mobility but should be optimized for low and medium speed users. Focus on streaming, interactive and background services. HSDPA new features should show significant incremental gains over existing R99 performance. Consider value added to the user, cost to the operators, increased revenue for operators, etc., in adding any new feature.HUAWEI TECHNOLOGIES Co., Ltd. Huawei ConfidentialPage 5 Page 5

OutlineIntroduction HSDPA New Techniques Transport and Physical Channels Spreading, Modulation and Coding Protocol Architecture Terminal Capabilities

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 6 Page 6

Power Utilization in HSDPAEfficient use of power: the unused power by dedicated/common channels is exploited by HS-DSCH with use of dynamic power allocation.

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 7 Page 7

Channel Sharing in HSDPAEfficient use of time: several packet data streams are time multiplexed and sent over High Speed Downlink Shared Channel (HS-DSCH).

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 8 Page 8

Major New TechniquesFast Scheduling Fast Hybrid ARQ Fast Link Adaptation

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 9 Page 9

Fast Scheduling

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 10 Page 10

Packet SchedulerThe packet schedulers task is to maximize the network throughput while satisfying the QoS requirements of the users.The packet scheduling method has significant impact on the cell throughput and on the user-perceived quality of service.

The scheduler is located in the Node B and can respond quickly to channel conditions, since the Iub and the RNC are not involved in the process. Multi-user diversity:Selection of the best users in the cell in terms of the UEs received signal strength is known as multiuser diversity. The scheduler may select for transmission in each TTI (Transmission Time Interval) users that have good signal to noise ratio and therefore ensure better data reception and fewer retransmissions. Multi-user diversity will increase the average cell throughput by using the network resources more efficiently.Channel Quality UE1 UE2

TTI intervals Node BUE2

UE1

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 11 Page 11

Scheduling MethodsRound RobinUsers are served in cyclic order ignoring channel conditions. It is simple and ensures a fair resource distribution among the users at the cost of cell capacity.

Maximum C/I (example shown in next page)The cell serves in every TTI the user with the largest instantaneous supportable data rate. Users with lower average radio conditions receive less resources but due to large fading dynamics, these users are still able to receive service.

Average C/IThe cell serves in every TTI the user with the largest average C/I that has data to be transmitted. Averaging windows can be as large as 50 TTIs. This tends to average the short term fading conditions for users.

Proportional FairnessThe cell serves the user with the largest relative channel quality, based on the short term data rate of the user relative to its average data throughput. Users with better short term channel conditions will have higher priority than users that are temporarily located in a fade.

Fair ThroughputModifies the proportional fair algorithm to increase the priority of users that receive lower average throughput, in an attempt to equalize the throughput to all users. A variant that does not use instantaneous channel quality information and serves in every TTI the user with the lowest average throughput.HUAWEI TECHNOLOGIES Co., Ltd. Huawei ConfidentialPage 12 Page 12

Example of Max C/I Scheduling MethodExample of Max C/I Scheduling

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 13 Page 13

Fast Hybrid ARQ

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 14 Page 14

Fast RetransmissionAll Release 99 (pre-HSDPA) transport channels are terminated at the RNC. Retransmission procedure is located in the serving RNC. The serving RNC (SRNC) may not be the controlling RNC (or drift RNC), and it may be several hops away from the controlling RNC, increasing response times.For high speed data, this potential delay is not acceptable.

The new high speed channel, the HS-DSCH, terminates at Node B. A new MAC layer, the MAC-hs, is introduced in the Node B in order to control all retransmissions in the high speed data channel and provide a quick response to channel errors.

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 15 Page 15

Hybrid ARQ TypesHARQ is an implicit link adaptation techniqueIt uses ACK/NACKS to produce correct packets (implicit adaptation to channel conditions). It uses samples weighted by the signal to noise ratio to combine received versions of the packets, which provides time-diversity.

There are three types of ARQ:Type I ARQ - a pure repetition mode, the original data block is retransmitted.Variants are called Chase Combining, when the data block is soft-combined with the original block and Optimum Combining, where each block is weighted by the signal to noise ratio and then combined.

Type II ARQ - This is called Full Incremental Redundancy (FIR) combining.A non-self decodable retransmission is sent. This retransmission must be combined with the original block in order to decode. It consists of parity bits and does not include the original data.

Type III ARQ - This is called Partial Incremental Redundancy (PIR)The retransmitted block must be self-decodable, that is, it must include the original version of the data in addition to any other redundant information.HUAWEI TECHNOLOGIES Co., Ltd. Huawei ConfidentialPage 16 Page 16

Fast Link Adaptation

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 17 Page 17

Link Adaptation by Transport FormatThe HS-DSCH does not use fast power control. The transmitted power in the HS-DSCH is substantially constant, depending on power sharing for other downlink channels in the Node-B. The adaptation to channel conditions is done by selection of the transport format, such as modulation and coding rate. The transport format may be changed every TTI (2 ms).UE Node B

Transport Format: Modulation and Coding Power measurement, CQI selection CQI report every 1 to 80 TTIs Transport Format selection, new modulation and coding

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 18 Page 18

Link AdaptationThe transmitter receives information on the channel conditions from the UE and selects an appropriate transport format for transmission.Selects QPSK or 16QAM modulation. Selects a specific coding rate that works well in those conditions (approximately a 10% block error rate). Lets the HARQ process fine-tune the coding rate by use of retransmissions to bring down the error rate.

Link adaptation is fast, since it all happens in the Physical layer between the UE and the Node-B. Example of Adaptive Modulation and Coding:

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 19 Page 19

OutlineIntroduction HSDPA New Techniques Transport and Physical Channels Spreading, Modulation and Coding Protocol Architecture Terminal Capabilities

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 20 Page 20

Channels and Layers

Radio Link Control (RLC) Layer 2 Logical Channels: Type of data sent Medium Access Control (MAC) Transport Channels: How data is sent Layer 1 Physical Layer

Physical Channels: Media used for data

HUAWEI TECHNOLOGIES Co., Ltd.

Huawei Confidential

Page 21 Page 21

Transport ChannelsTransport Channels

Dedicated Channels

Common Channels

Dedicated Channel (DCH) (Down & uplink)

Broadcast Channel (BCH) (Downlink) Forward-Access Channel (FACH) (Downlink)HUAWEI TECHNOLOGIES Co., Ltd.

Paging Channel (PCH) (Downlink)

Commo