Huawei HSPA+ Whitepaper V3[1].0 (20100810)

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Huawei HSPA+ White Paper

Issue V3.0

Date 2011-05-30

HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2008. All rights reserved.

No part of this document may be reproduced or transmitted in any form or by any means without

prior written consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd. All other

trademarks and trade names mentioned in this document are the property of their respective

holders.

Notice

The information in this document is subject to change without notice. Every effort has been made in

the preparation of this document to ensure accuracy of the contents, but all statements, information,

and recommendations in this document do not constitute the warranty of any kind, express or

implied.

Huawei HSPA+ White Paper V3.0

V1.0 (2011-05-30) Commercial in Confidence Page 3 of 40

Contents

1 Executive Summary .............................................................................................................. 4

2 HSPA+ Introduction ............................................................................................................. 6

3 Key Highlights of Huawei HSPA+ ....................................................................................... 8

3.2 Higher Order Modulation (HOM) at Air Interface ............................................................................... 9

3.3 Multi Input Multi Output (MIMO) ..................................................................................................... 10

3.4 Dual Cell & Dual Band HSDPA Technology ..................................................................................... 13

3.5 DC-HSUPA for Increased Uplink User Data Rate ............................................................................. 18

3.6 Continuous Packet Connectivity (CPC) ............................................................................................. 19

3.7 Voice over HSPA ................................................................................................................................ 21

3.8 Downlink Enhanced_Cell FACH ....................................................................................................... 24

3.9 Uplink Enhanced Cell_FACH ............................................................................................................ 25

3.10 Enhanced DRX in Cell_FACH (E-DRx) .......................................................................................... 25

3.11 HSPA+ Key Benefits ........................................................................................................................ 26

4 Huawei Specified Solutions for HSPA+ Issues ................................................................. 27

4.1 MIMO & Legacy Terminals Compatibility Solution ......................................................................... 27

4.2 Implementation of Advance Receivers ............................................................................................... 34

4.3 Implementation of Interference Cancellation (IC) ............................................................................. 36

5 Conclusion and Recommendations ................................................................................... 38

6 Acronyms and Abbreviations ............................................................................................. 39



1 Executive Summary

The popularity of Mobile Broadband (MBB) and data services is increasing

rapidly among the end users around the world. Huawei predicts that from 2010

and onward, global data traffic will increase many times compared to voice

traffic. A number of important factors are accelerating MBB adoption, these

include; flat charging rates, innovative smart phones, increased user awareness

and global coverage.

Deployment of HSPA+ and LTE networks along with the utilization of new

frequency bands can enable the mobile operators to reach these data traffic

requirements. HSPA+ & LTE will work as supporting technologies instead of

competitors to compensate these data demands. It’s easy to upgrade network to

HSPA+ within remaining the limited cost y to support higher capacity and data

demands.

As a key technology for mobile broadband, High Speed Packet Access (HSPA)

has been widely launched by WCDMA operators around the world. According to

different statistical analysts, currently HSPA is the biggest source for mobile

broadband. Informa Telecom and Media reported that in 2013, the numbers of

HSPA subscribers will reach to 900 millions worldwide, which will be 54% of

total MBB subscriptions.



HSPA+ is the evolution of HSPA and defined by 3GPP in release 7 and further

enhanced in its upcoming releases. The purpose of developing HSPA+ was to

increase the data and voice capacity of 3G network, improve users’ experience,

reduce service latency, extend UE battery time and decrease the cost of data

bits/sec so that HSPA could compete with other mobile broadband technologies,

and maintain its grip on the market.

HSPA+ deliver almost same peak data throughputs as in LTE in the limited

bandwidth of 5 MHz and 10Mhz. HSPA+ can be deployed in combination of more

than one carrier frequency as like as LTE to increase the network data

throughput capacity.

In general, HSPA+ enables the 3G technology to provide higher capacity data

and voice services.



2 HSPA+ Introduction

As a dominant mobile broadband technology, HSPA+ is top priority of most of the mobile

carriers around the world. Substantial increase in network data throughput and voice capacity

with the reduction of cost per bit is the reasons behind the huge popularity of HSPA+.

According to the GSA and Huawei wireless intelligence, up to the end of March 2010, more

than 90 operators committed to deploy HSPA+ and 45 of them have already deployed

commercial HSPA+ networks. Out of these operators, more than 60% have chosen Huawei as

key vendor due to its advance reliable end- to- end solution and high performance in HSPA

technology. This whitepaper provide key technologies and benefits of HSPA+. In addition, it

gives details of Huawei HSPA+ solution and feature deployment strategy roadmap.

HSPA evolution, feature adoption and implementation based on 3GPP standards roadmap is

given Figure 2-1.

Figure 2-1 HSPA+ 3GPP Standard roadmap and release dates

HSPA+ contain all the key features of legacy HSPA based on 3GPP R5 &R6 and add new

features based on 3GPP R7, R8, and R9.

3GPP Release 7 features for HSPA+ are:

Higher order modulation for uplink (16QAM) and downlink (64QAM)

Downlink MIMO (Multiple Input Multiple Output),



Enhanced CELL_FACH state (downlink)

Improved layer 2 support for high downlink data rates

Continuous Packet Connectivity (CPC）


Combination of MIMO and 64QAM

CS over HSPA

Dual Cell HSDPA

Improved layer 2 support for high uplink data rates

Enhanced CELL_FACH state (Uplink)

Enhanced DRx in CELL_FACH


Combination of MIMO , 64QAM and DCHSDPA in downlink

Dual Band DC-HSDPA (f1@ 900Mhz – f2:@2100Mhz, f1@ 1900Mhz – f2@ 2100Mhz,

f1@ 850Mhz – f2@ 2100Mhz)

DC-HSUPA

Transmit Antenna Array (TxAA)

In addition Multi carrier HSDPA will included for HSPA+ in 3GPP R10 standard.

The main purpose of introducing HSPA+ advance features is to increase the network data and

voice capacity and improve end user experience by providing high speed service.

Configuration of 64QAM based Higher Order Modulation (HOM) is the first and easy way to

increase cell and user data capacity. It requires only software change in the network to

support 64QAM. 1.4% increase in user data can be achieved by the introduction of 64QAM.

Due to the coverage challenges of 64QAM, it is necessary to use advance transmission

modes to provide higher data rate to the maximum of end users, especially in the middle and

edges of cells.

Use of Multi Input Multi Output (MIMO) and two or more carrier frequencies (DC/MC-

HSPA) can increase the throughput and quality of user data in all parts of the cell coverage

area. The combination of MIMO and DC-HSPA is important for the increase in peak and

average data rate of cell and end user.

Voice over HSPA is implemented to increase numbers of voice subscribers in a cell. The use

of high speed channels for voice service increases the voice capacity of a cell. VoIP over

HSPA and circuit switched voice over HSPA are the two solutions for voice over HSPA.

HSPA+ enhanced the end users’ experience by reducing the service latency and increasing

battery lifetime. This is realized by implementing advance interference cancellation

techniques like Continuous Packet Connectivity (CPC) and new channel mapping procedures

like enhanced cell FACH.

The coming sections of this document provide details of HSPA+ key features based on

Huawei RAN 13 (3GPP R9) and explain the purpose for deploying these features.



3 Key Highlights of Huawei HSPA+

Huawei has developed HSPA+ technology according to the 3GPP standards. Staring from

2009 as HSPA+ phase 1 based on 3GPP R7, Huawei is ready to commercialize HSPA+ phase

3 based on 3GPP R9 in first quarter of 2011. The first and 2nd phases of HSPA+ were

released in RAN11 and RAN12 in 2009 and 2010 consecutively. The third phase based on

3GPP R9 will be released in RAN13. Following figure is an overview of Huawei HSPA+

technology roadmap:

Figure 3-1 Huawei HSPA+ Solution Roadmap

The detailed descriptions along with the benefits of key features of HSPA+ are given in the

below sections:



3.2 Higher Order Modulation (HOM) at Air Interface

HSPA+ uses HOM techniques in both uplink and downlink to increase the number of bits per

data symbol and hence to increase the cell and user data throughput. In downlink, 64QAM

(Quadrature Amplitude Modulation) scheme is used along with 16QAM and in uplink

16QAM modulation scheme is adopted along with QPSK (Quadrature Phase Shift keying)

modulation. The details of QPSK, 16QAM and 64QAM along with their bits capacity per

symbol is given in Figure 3-2

Figure 3-2 Constellation Patterns for HSPA modulation schemes

.

By using 64QAM instead of 16QAM as modulation scheme in HSPA+ downlink, the number

of bits per symbol increase from 4bits to 6bits and hence the data rate of each HSDSCH code

increase from 960kbps to 1.4Mbps. The HOM of 64QAM can achieve 21Mbps data

throughput in the downlink. Table 3-1 gives comparison between 64QAM and 16QAM.

Table 3-1 –DL16QAM and 64QAM peak rate comparison

DL Modulation Scheme Maximum Peak Data Rate

64QAM 21 Mbps

16 QAM 14.4 Mbps

By using HOM of 16QAM instead of QPSK in the uplink increases the number of bits per

symbols and hence increases the uplink throughput. Table 3-2 gives the detail descriptions of

UL modulation schemes.

Table 3-2 – Comparison between HSPA UL modulation schemes

UL Modulation Scheme Maximum Peak Data Rate

16QAM 11.5 Mbps

QPSK 5.76 Mbps

3.2.2 Performance of 64QAM

64QAM can increase downlink data throughput at about 1.4 times of 16QAM.

However, 64QAM modulation can only be selected by UEs in very good radio

conditions and only near cell area. For example, in one of the deployed HSPA network

it was observed that UEs can select 64QAM in 20 to 25% of the HSPA cell and in the



rest of cell area; UEs could be able to only select16QAM and QPSK modulation

schemes.

Figure 3-3 Throughput and Coverage comparison of 64QAM

Due to less coverage of 64QAM it recommended to deploy 64QAM in small cell areas

to increase the cell throughput. For large cells, it is necessary to use new transmission

interface technologies such as MIMO and Dual Cell to provide high data throughput

service in middle and edges of the cells.

Huawei RAN solution requires software upgrade to evolve to 64QAM configuration.

3.3 Multi Input Multi Output (MIMO)

MIMO based on Transmit Antenna Array method is used in HSPA+ to enhance the cell data

throughput. MIMO uses two transmission paths and we can say that it doubles the data rate

compared to the traditional transmission techniques. MIMO when used together with

16QAM and 64QAM in a single cell can increase date rate to 28Mbps and 42Mbps

respectively. In addition, MIMO when used together with Dual Cell HSDPA, 84Mbps

downlink data rate can be achieved. Details of MIMO peak throughputs in combinations of

16QAM, 64QAM with single and dual cell configuration are given in Table 3-3.

Table 3-3 – MIMO peak data rate comparison

DL Configuration Peak Data Rate

2x2 MIMO + 16QAM (Single Cell) 28 Mbps




2x2 MIMO + 64QAM (Single Cell) 42 Mbps

2x2 MIMO + 16QAM (Dual Cell) 56 Mbps

2x2 MIMO + 64QAM (Dual Cell) 84 Mbps

The standardized MIMO transmission scheme is based on Adaptive Antenna Array. There are

two modes defined in standards:

1. TxAA, in this case one stream is transmitted over both antennas

2. D-TxAA or dual-stream TxAA, for this case, two separate data streams are transmitted

on two orthogonal weight sets simultaneously.

MIMO adopts the multi transmission and multi reception mode. Two transmit antenna in the

base station and two in the receiver side used to implement MIMO.

Through MIMO, either two independent data streams (transport block) or one data stream

can be transmitted over the radio channel through two antennas. The second data stream is

only turned on at high SINR conditions. In other words, either one data stream or two data

streams are transmitted depending on the terminal SINR conditions.

MIMO use spatial diversity and spatial multiplexing methods for transmitting single stream

and dual stream respectively. Both methods are adopted in the different scenarios but within

the same solution with spatial coding techniques.

For single stream the spatial diversity is used in MIMO. In spatial diversity mode, the same

signal is emitted from each of the transmit antennas with appropriate phase weighting such

that the signal power is maximized at the receiver input. The benefits of spatial diversity are

to increase the received signal gain, by making signals emitted from different antennas add

up constructively, and to reduce the multipath fading effect.

For dual stream data transmission spatial multiplexing is used in MIMO. Spatial multiplexing

is used to split high rate signals multiple lower rate streams and each stream is transmitted

from a different transmit antenna in the same frequency channel. Spatial multiplexing is

always adopted in high signal to noise conditions.

UE feedback Pre-coding Control Information (PCI) and Channel Quality Indicator (CQI)

report to the NodeB for the selection of single or dual streams MIMO. Based on the

composite PCI/CQI reports, the base station scheduler decides whether to schedule one or

two data streams to the UE and what packet sizes and modulation schemes to use for each

stream.

The details of MIMO working principles are given in Figure 3-4.



Figure 3-4 – MIMO working principle

MIMO improves the data throughput rate in all coverage area of the cell and provide better

user throughput in near cell and edge of cell.

Figure 3-5 – MIMO Throughput and Coverage Comparison

Huawei MIMO based specified Remote Radio Unit (RRU) transceivers can support MIMO

within one module.



Figure 3-6 – Huawei Solution for MIMO based on Single RF Transceiver (RRU)

In MIMO transmission, the Common Pilot Channel (CPICH) has to be transmitted from both

antennas. Commonly pilot channel is sent on two antennas by using the same spreading

factor and scrambling code and differentiated with Space Time Block Codes. This type of

transmission is similar to Space Time Transmit Diversity (STTD) mode defined for R99 by

the 3GPP.

It is observed that the pilot channel detection for the non-MIMO UE (having both RAKE and

Equalizer receiver) camping in the MIMO cell is difficult in STTD mode and huge

throughput and performance loss is noticed for the non-MIMO terminals. UEs deactivates the

equalizer functionality whenever transmit diversity is used in the system following some

compromise design in the receiver chipset. The reason behind this drawback is the lack of

sufficient processing power to be able to sustain both techniques simultaneously in the

chipset. Therefore Primary & Secondary Pilot (PSP) mode of pilot channel is introduced by

Huawei for the MIMO solution. For more details, see “Huawei Specified Solutions for

HSPA+ Issues”.

Following are the two modes of pilot channels transmission:

1. STTD Mode (The Pilot channels for each antenna are differentiated by block codes but

with same channelized codes). In STDD, single pilot is used for MIMO and non-MIMO UEs.

2. Primary & Secondary Pilot (PSP) Mode (The Pilot channels for each antenna are

differentiated by channelized codes). In PSP mode, separate pilots are used for MIMO and

non-MIMO UEs

3.4 Dual Cell & Dual Band HSDPA Technology

HSPA+ data can also be transmitted by the combination of two or more carriers and this

result in double or more times of data throughput. In 3GPPR8 standard, it was only allowed

to uses two carriers of consecutive frequencies in downlink and named as Dual Cell HSDPA

(DC-HSDPA). However, in 3GPP R9 it is standardized to use different frequency bands (e.g.

one cell of 900 MHz and second cell of 2100 MHz) for each cell and named as Dual Band

HSDPA (DB-HSDPA). The operation of DC and DB-HSDPA is almost same; but with only

following three differences:

1. DC-HSDPA can only use one frequency band (e.g. 900 MHz or 2100 MHz) with

consecutive carriers



2. DB-HSDPA uses two frequency bands (e.g. one carrier of 900 MHz and second carrier

of 2100 MHz).

3. DB-HSDPA cells cannot be configured for DB-HSUPA but the DC-HSDPA cells can be

configured as DC-HSUPA

If both the network and the user equipment are capable of Dual-Carrier HSDPA operation,

the network will be able to configure the user equipment not only with a (primary) serving

cell but also with a secondary serving cell originating from the same base station.

DC/DB-HSDPA uses two cells for transmitting data for every user. The purpose of

developing DC/DB-HSDPA is to improve users’ experience by providing quality of data

service to all the users across the cell and especially at the cell edges. The deployment of a

second HSDPA carrier creates an opportunity for network resource pooling as a way to

enhance the user experience, particularly when the radio conditions are such that existing

techniques are not effective in limited 5 MHz band.

3.4.1 Dual Cell HSDPA (DC-HSDPA)

Through dual cell transmission and using double radio resource, DC-HSDPA is able to

provide higher data throughput to the end users and better results can be obtained in the cell

edges. Figure 3-7 shows the working principles of DC-HSDPA

Figure 3-7 – DC-HSDPA working principle

One of the two cells is treated as anchor (primary) cell and the other one as supplementary

(secondary) cell and both of them can be deployed with equivalent and non-equivalent

channel configuration.



Figure 3-8 – Equivalent and non- equivalent deployment of Primary and Secondary cells

In equivalent deployment, both the cells can work as anchor and supplementary cells for the

DC subscribers in the same coverage area. Some of the subscribers will treat one cell as their

anchor cell and rest of them will treat second as their anchor cell. The selection of the anchor

carrier is based on cell load and operators Radio Barer (RB) strategy. The anchor carrier

always initializes the handover process of an end user and supplementary carrier is not

involved in handover process. In addition, both the cells will work as an independent single

cell source for the non-DC-HSDPA subscribers and legacy HSDPA subscribers. In

non-equivalent deployment, the supplementary cell is configured with one HS-DSCH and a

P-CPICH; in this case, the supplementary cell cannot serve traditional HSDPA, HSUPA and

R99 users in standalone operations. In both equivalent and non-equivalent deployment, the

legacy HSDPA service will not be interrupted after the introduction of DC-HSDPA in the

network.

_________________________________________________________________

Note:

Huawei strongly recommend Equivalent Deployment configuration and all the details in this

document are based on equivalent deployment configuration.

_________________________________________________________________

The implementations of DC-HSDPA along with 64QAM and MIMO provide 84Mbps peak

downlink data rate.

Details of DC-HSDPA peak throughputs in combinations of 16QAM and 64QAM

modulation schemes are given in Table 3-4.

Table 3-4 – DC -HSDPA peak data rate comparison


DC-HSDPA + 16QAM (without MIMO) 28 Mbps

DC-HSDPA + 64QAM (without MIMO) 42 Mbps

DC-HSDPA + 64QAM (with MIMO) 84Mhps



Figure 3-9 – DC-HSDPA Throughput and Coverage Comparison

DC-HSDPA has best coverage and better throughput in cell edges compared to all other

features of HSPA+ due to double frequency resource utilization.

Huawei multi carrier technology easily enables to evolve and deploy DC-HSDPA. Huawei

was the first vendor to provide multi carrier transceivers to the industry. Most of the deployed

UMTS networks by Huawei are configured with multi carrier transceivers, so it is easy for

those operators to upgrade their network for DC-HSDPA and future MC-HSDPA.

Figure 3-10 – Huawei Multi Carrier Benefits for DC-HSDPA Operations

_________________________________________________________________

Note:

The operation of DC-HSDPA service is dependent on terminal support and new UE type is required.

However, as both cells of DC-HSDPA can also operate as a single HSPA source cell and hence all

types of HSPA UEs will be supported by the individual cell. DC-HSDPA UEs are expected to be

available in 2010.

_________________________________________________________________



3.4.2 Dual Band HSDPA (DB-HSDPA)

DB-HSDPA operation procedure is same as DC-HSDPA but with different operation

frequency band for each carrier. An HSDPA user in DB-HSDPA cell uses two

frequency carriers in two different bands within the same NodeB. The selection of

carriers can only be configured according to the combination of limited bands as given

in Table 3-5.

Table 3-5 – DC – DB- HSDPA allowed frequency band combination

DB-HSDPA

Configuration

Uplink Band Downlink Band

1

I or VIII

I and VIII (2100Mhz &

900Mhz)

2

II or IV II and IV (1900Mhz &

AWS)

3

I or V

I and V (2100Mhz &

850Mhz)

The working principle and channel configuration of DC-HSUPA technology is given

in Figure 3-11.

Figure 3-11 – DB-HSDPA Working Principle and Channel Configurations

The Anchor and Supplementary carrier configuration is same as DC-HSDPA. DB cells

can be configured as MIMO and DC-HSUPA but a UE cannot use DB-HSDPA,

MIMO and DC-HSUPA simultaneously. The theoretical user peak data for Dual band

HSDPA in combination with 16 and 64QAM modulation scheme is given in Table 3-6.

Table 3-6 – DB -HSDPA peak data rate comparison


DB-HSDPA + 16QAM 28 Mbps

DB-HSDPA + 64QAM 42 Mbps



_________________________________________________________________

Note:

The operation of DB-HSDPA service is dependent on terminal support and DC-HSDPA UEs cannot

support DB-HSDPA so new UE type is required. However, as both cells of DB-HSDPA can also

operate as a single HSPA source cell and hence all types of HSPA UEs will be supported by the

individual cell. DB-HSDPA UEs are expected to be available in 2012.

_________________________________________________________________

3.5 DC-HSUPA for Increased Uplink User Data Rate

In order to improve the uplink data throughput rate for each user and to utilize the

benefits of dual cell technology, DC-HSUPA based on 3GPP R9 standard along with

E-DPCCH boosting is implemented in Huawei RAN13.

DC-HSUPA will ensure the uplink data rate regardless of modulation scheme

constrains and help users to transmit high data rate service in uplink. Through

DC-HSUPA an HSUPA user use two carriers in uplink, one of the carrier is treated as

Anchor carrier and the other as Supplementary carrier. Anchor carrier is always

connected to the UE and responsible for handover and mobility procedures. Both the

primary and secondary carrier can individually support HSUPA service and can

support all types of HSUPA terminals. In Huawei RAN13 (based on 3GPP R9),

DC-HSUPA can only be configured to the consecutive frequency cells of the same

band. DC-HSUPA can also be configured to the MIMO based cells. The working

principle and channel configuration of DC-HSUPA technology is given in Figure 3-12.

Figure 3-12 – DC-HSUPA Working Principle and channel configuration

UE transmit uplink data with E-DCH on two adjacent carriers. Since every carrier has

independent close loop power control so DPCCH will be transmitted on each carrier.

NodeB independently schedule UE on each carrier and the process is dependent on

DC-HSDPA service as well. In addition, 2ms TTI is required for the operation of

DC-HSUPA.

The peak data rate for Dual band HSUPA in combination with QPSK and 16QAM

modulation scheme is given in Table 3-7.



Table 3-7 – DC -HSUPA peak data rate comparison

UL Configuration Peak Data Rate

DC-HSUPA + QPSK 11 Mbps

DC-HSUPA + 16QAM 23 Mbps

_________________________________________________________________

Note:

The operation of DC-HSUPA service is dependent on terminal support so new UE type is required.

However, as both cells of DC-HSUPA can also operate as a single HSUPA source cell so all types of

HSUPA UEs will be supported by the individual cell. DC-HSUPA UEs are expected to be

commercialized in 2012.

_________________________________________________________________

3.6 Continuous Packet Connectivity (CPC)

CPC is a combination of features that are used to ensure the quality and performance of data

and voice subscribers in HSPA+ network. Especially, CPC reduce the interference level by

different means in the HSPA+ cell and increase the battery lifetime of the user terminal. CPC

helps users to stay long time in connected mode so that users can experience always online.

CPC consists of following features:

3.6.1 Uplink Discontinuous Transmission (DTX)

Uplink control channels are important to maintain synchronization. However, the uplink

control channels contribute to the overall uplink noise rise. This includes both the Uplink

Dedicated Physical Control Channel (DPCCH) and the High Speed Dedicated Physical

Control Channel (HS-DPCCH). Thus, one aim of CPC is to reduce the uplink control channel

overhead for both DPCCH and HS-DPCCH.

UL-DTX allows the UE to stop transmission of uplink DPCCH in case there is no

transmission activity on E-DCH or HS-DPCCH. This is sometimes also called uplink

DPCCH gating. Uplink DPCCH is not transmitted continuously any more, but it is

transmitted from time to time according to a known activity pattern. Figure 3-13 shows the

working principle of uplink DTX.

Figure 3-13 – DPCCH discontinuous pattern

A new uplink DPCCH slot format is introduced in order to further reduce uplink control

channel overhead. It contains only six pilot bits and four TPC (Transmit Power Control) bits

in order to reduce DPCCH transmit power. FBI (Feedback Information) and TFCI (Transport

Format Combination Indicator) bits are not sent. Figure 3-14 shows DPCCH new slot format.



Figure 3-14 .- DPCCH new slot format

3.6.2 Downlink Discontinuous Reception

In HSDPA of 3GPP release 5, the UE has to monitor the HS-SCCH continuously in order to

know the possible downlink data allocations. In HSPA+, the network can limit the number of

sub-frames where the UE has to monitor the HS-SCCH in order to reduce UE battery

consumption. The DRX operation is controlled by the parameter UE_DRX_cycle that is

configured by higher layers and can take values of 4, 5, 8, 10, 16, or 20 sub-frames. For

example, if UE_DRX_cycle is 5 sub-frames, the UE only monitors the HS-SCCH on every

5th sub-frame.

Figure 3-15 – Downlink DRX pattern

3.6.3 HSSCH less Operations

In HSDPA as defined from 3GPP release 5 onwards, UE is supposed to read continuously on

HS-SCCH where data allocations are being signaled on HS-DSCH. The UE is being

addressed via a UE specific identity (16 bit HRNTI / HSDPA Radio Network Temporary

Identifier) on HS-SCCH. As soon as the UE detects relevant control information on

HS-SCCH it switches to the associated HSPDSCH resources and receives the data packet.

In HSPA+, the conventional process is changed by HS-SCCH less operations and base station

decides whether to use HS-SCCH or not. The first transmission of a data packet on

HS-DSCH can be done without an associated HSSCCH. If the packet is not received in the

initial transmission, the base station may retransmit it and the retransmission will use

HS-SCCH signaling.

HS-SCCH less operation reduces the HS-SCCH overhead, reduces UE battery consumption,

and improves the UE online connection mode. HS-SCCH less operation is optimized for

services with relatively small packets, e.g. VoIP and conventional operation is always

possible along with HS-SCCH less operation for large packet services. Figure 3-16 shows

HSCCH less operations principle.



Figure 3-16 – HSCCH less operations principle

Key benefits of CPC are given in Figure 3-17.

Figure 3-17 – CPC benefits

3.7 Voice over HSPA

Voice services over wireless networks have traditionally been provided by circuit-switched

(CS) service where a dedicated channel is used for each voice call. This provides guaranteed

Quality of Service (QoS) in terms of end-to-end delay for the voice traffic; however, the

capacity is limited since the resources for a dedicated channel are always occupied even

though they are only used when the voice traffic is being carried out.

HSPA+ allow integration of data services with voice services and thus provide higher

network bandwidth efficiency, better manageability and cost savings as well as richer

services. Carrying voice over a shared packet transport provides better utilization because a

voice user uses the shared resources only when it is active.

HSPA+ uses two new techniques Circuit Switched (CS) voice over HSPA and VoIP over

HSPA along with the traditional voice over DCH based on 3GPP R99. Instead of using DCH



channels as in WCDMA R99 voice, voice over HSPA uses HSPA bearers that increase the

capacity of HSPA cell. The use of DCH in a cell can be minimized by voice over HSPA and

thus more power and code resources are available for HSPA service. Users will enjoy 50%

more talk time without compromising battery lifetime, while operators now can flexibly mix

voice and data services on the same HSPA+ carrier. The efficiency of voice services

dependent on HSPA+ feature of Continuous Packet Connectivity (CPC). CPC reduce intra

cell interference by gating off control channels and applying discontinuous transmission and

reception techniques.

VoIP over HSPA call flow follow packet core network and IMS but CS over HSPA follow

legacy CS core network. Call flow procedure of CS over HSPA and VoIP over HSPA is given

in Figure 3-18.

Figure 3-18 – VoIP and VoCS over HSPA call flow

3.7.2 CS over HSPA

CS voice over HSPA takes the mobile circuit voice service, using the circuit core switches in

the network and tunnels it over an underlying IP bearer. So the application is not VoIP, but

circuit telephony while the wireless transport is IP.

The implementation of CS over HSPA in current 3G HSPA networks requires relatively

minor changes at the radio access. These modifications can be introduced by software

upgrades. As voice service are more delay sensitive so de-jitter buffers at both the RNC and

UE as well as a delay sensitive scheduler at the NodeB are introduced to support CS over

HSPA.

Through CS over HSPA 48% more subscribers can be accommodated in a cell as compared

to R99 service. Figure 3-19 shows the ratio of VoCS over HSPA users compared to voice

over DCH (R99).



Figure 3-19 – VoCS vs VoDCH cell voice capacity comparison

This operability of this service is dependent of handsets based on 3GPPR8 that are expected

to be available in 2010.

_________________________________________________________________

Note:

A famous terminals vendor has committed to provide CS Voice over HSPA terminals and the

expected commercial available time is 2011.

_________________________________________________________________

3.7.3 VoIP over HSPA

VoIP over HSPA also increase the cell voice capacity as by moving voice traffic over to these

high-speed data channels. While deploying VoIP with HSPA, operators can smoothly migrate

their users from circuit-switched operation to packet-switched operation over time. As the

UMTS radio channel supports both circuit-switched voice and packet-switched data, some

voice users can be on legacy circuit-switched voice and others can be on VoIP.

VoIP over HSPA require IMS entity in the core network and it is mandatory to add IMS in the

network. Call f low of VoIP over HSPA is already given in figure. Through VoIP over HSPA,

45% more users can be accommodated in one cell as compared to voice over DCH (R99).

Figure 3-20 shows the ratio between VoIP over HSPA and voice of DCH users in a cell.



Figure 3-20 – VoIP vs VoDCH cell voice capacity comparison

As like VoCS over HSPA, VoIP over HSPA service also rely on UE support and its expected

that these types of UEs will be available in 2011 or later.

3.8 Downlink Enhanced_Cell FACH

Cell FACH state is very useful for a UTRAN system to provide low data rate services such

like push email and always-on experience to end users. In 3GPP R5 and R6 standards,

HSDPA data service cannot be provided in Cell FACH state and user need to change its state

from Cell_FACH to Cell_DCH for transmitting or receiving HSDPA data. This creates data

delay as well as frequent state transitions, which increase the signaling burden the UTRAN.

In HSPA+ by using Downlink Enhanced_Cell FACH feature, HSDPA data can be transmitted

in Cell_FACH state and control channels are mapped with on HS-DSCH channels. This saves

the unwanted state transition and signaling procedure and improves network capability and

users experience.

In Enhanced_Cell FACH, the logical channels and traffic channels are mapped on HS-DSCH

channel instead of FACH channel. This improves the state transition time of user from

connected to active mode. The user can receive high-speed data while remaining in the

FACH state. Figure 3-21 and Table 3-8 show procedure and advantages of enhanced cell

FACH.

Figure 3-21 – Enhanced Cell FACH procedure and delay advantages



Table 3-8 – Enhanced cell FACH advantages

Enhanced Cell FACH Improvements

FACH R99 FACH on HSDSCH

Data Rates 32Kbps >1 Mbps

Transition time of

Cell_DCH

> 600ms ≤ 130ms

Advantages Improve user’s experience , decrease call setup delay and HTTP

response time

3.9 Uplink Enhanced Cell_FACH

Only DL-Enhanced Cell FACH cannot be fully beneficiary for UTRAN unless it is also

supported by uplink Enhanced_Cell FACH. This is because of frequent uplink random

accesses signaling messages created by the UE during state transition. The uplink signaling

massages could create huge signaling delay before the actual data transmission. In order to

reduce the signaling burden and delay cause by the UE during frequent state transition

between Cell_DCH and Cell_FACH in uplink, Enhanced uplink Cell_FACH is necessary to

support enhanced downlink Cell_FACH procedure. In Enhanced uplink Cell_FACH, the

uplink HSUPA data can be transmitted in FACH state and all the control channels are mapped

on EDCH channel.

The implementation of Enhance Cell_FACH along with DL Cell_FACH reduces the

signaling delay and signaling excess.

3.10 Enhanced DRX in Cell_FACH (E-DRx)

The key constrain of always-on or connected mode services is users’ battery lifetime. In

enhanced Cell_FACH where the user remains in connected mode for most of the time, it is

required to adopt UE power saving techniques in Cell_FACH state.

UE Discontinuous Reception (DRX) in Enhanced Cell_FACH mode is adopted to reduce the

UE battery usage and to increase the UE power efficiency.

UE power saving function will also help in decreasing the signaling messaging procedure

between network and UE, as UE will no longer frequently change its state from Cell_FACH

to Cell_PCH or idle mode to save battery power.

In Enhanced _cell FACH, the NodeB and UE remain in connected mode regardless of data

transmission, but in DRX mode, UE stop all types of reception including channel decoding

and demodulation when it has no data requests. The procedure of DRX in Enhanced_Cell

FACH is given in Figure 3-22.



Figure 3-22 – DRX procedure in Enhanced Cell FACH

By DRX function in Enhanced Cell_FACH, 40 to 60% of the UE power could be saved.

3.11 HSPA+ Key Benefits

Table 3-9 – HSPA+ key features and their benefits

HSPA+ Key Features Benefits

Higher Order Modulation

(DL64QAM, UL16QAM)

50% downlink cell data throughput capacity and doubles

uplink data capacity

Multi Input Multi Output

(MIMO)

Double downlink cell data throughput capacity

Dual Carrier/ Multi Carrier

HSPA (DC/MC HSPA)

Double cell throughput capacity, improved user

throughput in cell edges, better user experience in the

whole cell

Voice over HSPA 48% more voice capacity when use CS voice over HSPA

and 45% more capacity when use VoIP over HSPA

Enhanced Cell FACH and DRX`

in Enhanced Cell FACH

Improved state transition time, faster call setup, low

latency. 40 to 60% of UE power can be saved

Continuous Packet Connectivity

(CPC)

Lower interference, improved user experience, increase

voice capacity



4 Huawei Specified Solutions for HSPA+

Issues

HSPA+ also encountered some deployment, up gradation, compatibility and traffic balancing

problems that required deep research to address and to solve. Below sections describes the

details and solution of HSPA+ main issues:

4.1 MIMO & Legacy Terminals Compatibility Solution

MIMO deployment requires transmit antenna diversity techniques in the Base Station and

data is transmitted by two antennas in the downlink. In the first solution for MIMO, block

coding techniques are used to differentiate the pilot channels of the two transmit antennas

which is similar to the Space Time Transmit Diversity (STTD) mode of R99.

As most of the legacy HSDPA UEs contains RAKE and Equalizer receivers in their chipsets,

it’s difficult for them to use equalizer in STTD mode. The reason behind this drawback is the

lack of sufficient processing power to be able to sustain both the equalizer and RAKE

techniques simultaneously in the chipset. Thus, UEs deactivate the equalizer functionality

whenever transmit diversity is used in the system.

It is observed that in a MIMO based cells, the legacy UEs also deactivate their equalizer

receivers when pilot channel is transmitted in the STTD pattern. As equalizer is an advance

receiver and its efficiency is very high compared to the RAKE receiver so the total

throughput supported by legacy non-MIMO terminals reduced largely and hence 30%

average cell throughput decreases in this case compared to non-MIMO cell. This means that

the non-MIMO terminals perform worse in MIMO cells compared to their normal mode.

Figure 4-1 shows the throughput loss of Non-MIMO terminals in MIMO cell in STTD mode:



Figure 4-1 – Legacy HSDPA ( cat 10- type 3) terminals Performance in MIMO-STTD Cell

In STTD mode of pilot channel transmission, it is not possible to get standard throughput

from the legacy HSDPA users as like as in normal cases.

_________________________________________________________________

Note:

The performance loss problem is only encountered in cat 10 and below HSDPA devices; all HSPA+ and

MIMO terminals have no performance loss issue in MIMO cells. The performance loss of UE based on of

type 2-receiver is worse than type 3 in a MIMO cell.

The details of UE receiver types is given in the below:

The Equalizer is an advance receiver and has better performance than RAKE as it effectively kills ISI (Inter

Symbol Interference). Linear Minimum Mean Square Error (LMMSE) equalizers are used in UE receivers

The details of HSDPA UE categories along with the type (cat type) are given in the below table:





Description of Radio conditions:

Good Radio conditions: RSCP > -70 and CQI > 23

Medium Radio Conditions: -90< RSCP < -70 and 15 < CQI < 20

Bad Radio conditions: RSCP < -90 and CQI < 15

_________________________________________________________________

In order to solve this issue, the Primary and Secondary Pilot (PSP) Channel solution is

introduced instead of STTD mode. The PSP mode uses different chanalized codes for each

pilot channel transmitted from each antenna. This means that legacy HSDPA devices will be

able to use only P-CPICH for channel estimation through single antenna and will no longer

rely on the second antenna for pilot and channel estimation. Figure 4-2 shows the channel

configuration of PSP mode.



Figure 4-2 – PSP Mode Channel Configuration

However, when the HSDPA terminals are tested in PSP mode, it is also noticed that the

current existing non-MIMO terminals again cannot produce the standard throughput

according to their capacity and normal use.

Figure 4-3 shows throughput results comparison of HSDPA cat-10 (type 3 receiver) device in

PSP and non-MIMO cells.

Figure 4-3 – Legacy HSDPA UE ( cat10-type3) throughput comparison in MIMO-PSP and 1TX

(non-MIMO ) based cells

Interference caused by non-equivalent power delivery from the 2nd

antenna cause this

problem. PA loads become unbalance due to different channels configurations and secondary

PA cause interference to legacy terminals. Figure 4-4 shows the power transmission

comparison between primary and secondary power amplifiers for transceivers.



Figure 4-4 – Transceivers PA Power Comparison for Primary and Secondary Pilot Channels

The PSP could be the only solution for legacy HSDPA terminals when used in MIMO cells,

so this solution required to be optimized for the reducing all performance losses.

Huawei used new interference cancellation techniques along with Virtual Antenna Mapping

(VAM) solution to reduce the interference caused by the secondary antenna and reduce the

loss in legacy HSDPA throughput. Figure 4-5 shows the overview of Huawei MIMO &

legacy HSDPA co-carrier solution.

Figure 4-5 –Overview of Huawei Co-Carrier Solution for MIMO & legacy Terminals

Intelligent Interference Control ( IIC )

IIC is a special interference cancellation technique designed by Huawei and used as a

part of Radio Resource Management (RRM). This is property of Huawei Technologies

and undisclosed to other vendors.

Virtual Antenna Mapping (VAM )

VAM is a standard solution for antenna mapping and original signal on each antenna

are cross-connected before transmission. VAM balance the load between the two

amplifiers and reduce interferences.



Figure 4-6 shows the results of solution for cat-10 (type-3 receiver); the performance loss is

largely reduced as compared to all the past solutions. HSDPA legacy devices averagely suffer

less than 6% in MIMO cell which is affordable as compared to the MIMO gain.

Figure 4-6 – Legacy HSDPA Terminals (cat10-type3) Performance in Huawei MIMO Solution

_________________________________________________________________

Note:

The performance for HSDPA legacy users’ loss can be fully eliminated to 0% by adaptive adjustment of

throughput levels according to the users’ penetration percentage. In the early stage when MIMO users’

penetration is less, the priority can be given to non-MIMO users and their loss can be controlled.

This solution based on users’ priority with new algorithm is under trial and expected to be available in end of

Q3-2010.

Along with cat-10 type 3, cat-10 type 2, cat-8 type 3 and ca-8 type 2 UEs has also performance benefits from

Huawei MIMO solution.

Through MIMO solution, the overall average cell throughput gain compared to single TRX

solution is more than 20% and users’ throughput gain is more than 31%.



Figure 4-7 –MIMO User Throughput gain compared in Huawei Solution

4.2 Implementation of Advance Receivers

In early WCDMA systems, the traditional RAKE receivers are adopted at Base Stations to

meet initial capacity and coverage requirements. The rake receiver can combine limited

number of multipath signals (4 to 8) and hence can support less than 6Mbps HSUPA data.

But, to support high uplink throughputs based on 3GPP R7, the receiver must need to

combine large number of multipath signals and also strong capabilities for cancelling ISI

(Inter Symbol Interference) caused by these multipath signals. Traditional RAKE receiver

cannot satisfy the performance requirements for 16QAM based HSUPA.

Thus, many advanced receivers, such as; Frequency Domain Equalization (FDE),

Generalized RAKE (GRAKE) and Liner Minimum Mean Square Error (LMMSE) have been

proposed to improve capacity of HSUPA network by suppressing interference.

Huawei has adopted FDE as an advance receiver to improve the performance of HSUPA

networks. FDE adopts Fast Fourier Transform (FFT) operation to perform signal equalization

in the frequency domain and significantly reduce the ISI and improves the system

performance. FDE equalize the received signals before combining and remove maximum

of interferences created by multiple symbols during the multipath reception. Figure 4-8 and

Figure 4-9 show the overview of FDE implementation purpose and benefits.



Figure 4-8 Overview of FDE Implementation Purpose

Figure 4-9 FDE vs RAKE receiver (Working Principle and Performance)

Its necessary to adopt FDE receiver is when deploy 16QAM in uplink for HSUPA, otherwise

the high peak and average throughput from 16QAM HSUPA cannot be achieved.



According to Huawei simulations, FDE based receiver can increase user data rate from 22%

to 36% as compared to the RAKE based receiver.

4.3 Implementation of Interference Cancellation (IC)

The use of higher order modulation scheme in uplink requires more transmission power. This

increase in uplink power by high data users creates more noise or interference to their

neighboring users, as interference is directly proportional to the user transmission power.

This rise in noise could affect the data capacity and limit the coverage of the uplink services.

For more than 5Mbps data throughput, >10dB transmission power is required and it can

create 10 to 14dB noise. So interference cancellation is required to reduce down the noise or

interference level.

Interference Cancellation (IC) algorithm based on Multi User Detection (MUD) techniques is

used in Huawei solution to reduce Multiple Access Interference (MAI) created by high

throughput based users. IC is imposed on the HSUPA E-DCH channel to reduce the

interference created by the high data rate users and its impact on the neighboring data and

vice users in uplink. E-DCH IC here means adopting IC on E-DPDCH. IC is specially

implemented to reduce the UL interference created by the high bit rate users. Continuous

Packet Connectivity (CPC) with uplink channel gating off function is used to reduce

interference created by the low bit users. IC insures the uplink capacity and coverage for data

users in the HSUPA network. IC is implemented in NodeB and has no impact on any other

network elements in Radio Access Network (RAN). Figure 4-10 shows an overview of IC

implementation.

Figure 4-10 – Overview of IC implementation benefits

Figure 4-11 and Figure 4-12 shows the benefits of IC for improving data throughput services

in the uplink.



Figure 4-11 –IC implementation benefits for Cat-5 HSUPA UEs

Figure 4-12 –IC implementation benefits for Cat-6 HSUPA UEs

According to Huawei simulations, IC can increase more than 40% of cell throughput for

10msec TTI based UE and 35% of the cell throughput for 2ms TTI based UE as compared to

the non-IC solution.



5 Conclusion and Recommendations

HSPA+ will be the dominant mobile broadband technology for the coming era

and will remain the top priority of most of the mobile carriers around the world.

Substantial increase in network data throughput and voice capacity along with

the reduction of cost per bit is the key advantages of HSPA+.

Higher order modulations, Multi Input Multi Output, Dual Cell transmission and

combinations of all of these provide high data throughput for the end users as

compared to the legacy HSPA.

The voice over HSPA along with the Continuous Packet Connectivity doubles the

network voice capacity and improves users’ experience.

In general trend HSPA+ is identified as pre LTE technology because in limited

bandwidth its throughput and performance matches to that of LTE.

Huawei is one of the top vendors who early achieved the HSPA+ technology

maturity and deployed commercial network by not only providing end-to-end

network but also the users’ terminals. Until now, Huawei has deployed more than

60% of total commercial and pre-commercial HSPA+ networks worldwide.

Huawei is adopting the smart network architecture and packet inspection

techniques to make HSPA+ more profitable for the operators.

The huge market shares reflect the strength and maturity of Huawei in HSPA+

technology.



6 Acronyms and Abbreviations

Table 6-1 Acronyms and Abbreviations

Acronym and Abbreviation Expansion

3G The Third Generation

AMR Adaptive Multi-Rate

ARQ Automatic Repeat Request

AQM Active Queue Management

BBU Baseband Unit

BITS Building Integrated Timing Supply System

BTS Base Station

CCCH Common Control Channel

CPC Continuous Packet Connectivity

CPICH Common Pilot Channel

CQI Channel Quality Indicator

DL Downlink

DPCCH Dedicated Physical Control Channel

DPDCH Dedicated Physical Data Channel

DRX Discontinuous Reception

DTCH Dedicated Traffic Channel

DTX Discontinuous Transmission

DTxAA Double Transmit Antenna Array

EDCH Enhanced Dedicated Channel

FACH Forward Access Channel

HSDPA High Speed Downlink Packet Access



Acronym and Abbreviation Expansion

HSUPA High Speed Uplink Packet Access

HARQ Hybrid Automatic Repeat Request

HS-PDSCH High Speed Physical Downlink Shared Channel

HS-SCCH High Speed Shared Control Channel

MIMO Multi-Input Multi-Output

MAC Medium Access Control

PA Power Amplifier

PARC Platform Advanced Radio Control

PDU Protocol Data Unit

QAM Quadrature Amplitude Modulation

RAN Radio Access Network

RET Remote Electrical Antenna

RNC Radio Network Controller

RLC Radio Link Control

RRM Radio Resource Management

SAE System Architecture Evolution

SISO Single Input Single Output

TPC Transmit Power Control

TrCH Transport Channel

UL Uplink

VoCS Voice over Circuit Switch

VoIP Voice over IP

WCDMA Wideband Code Division Multiple Access

Documents

Huawei HSPA+ Whitepaper V3[1].0 (20100810)