MIMO

WCDMA RAN

MIMO Feature Parameter Description

Copyright © Huawei Technologies Co., Ltd. 2010. All rights reserved.

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Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

WCDMA RAN MIMO Contents

Issue 01 (2010-06-20) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

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Contents 1 Introduction ................................................................................................................................1-1

1.1 Scope ............................................................................................................................................ 1-1 1.2 Intended Audience ........................................................................................................................ 1-1 1.3 Change History.............................................................................................................................. 1-1

2 Overview of MIMO.....................................................................................................................2-1

3 Basic Principle...........................................................................................................................3-1 3.1 Overview ....................................................................................................................................... 3-1 3.2 HS-DPCCH Changed for MIMO.................................................................................................... 3-2

3.2.1 Overview............................................................................................................................... 3-2 3.2.2 ACK Reporting...................................................................................................................... 3-3 3.2.3 PCI Reporting ....................................................................................................................... 3-4 3.2.4 CQI Reporting....................................................................................................................... 3-4

3.3 HS-SCCH Type 3 .......................................................................................................................... 3-6 3.4 Pilot Transmit Mode ...................................................................................................................... 3-7

3.4.1 Overview............................................................................................................................... 3-7 3.4.2 Pilot Transmit Diversity ......................................................................................................... 3-8 3.4.3 Primary/Secondary common Pilot (PSP) ............................................................................. 3-8

3.5 Enhanced Messages for MIMO..................................................................................................... 3-9 3.5.1 Enhanced Messages for MIMO on Iub Interface.................................................................. 3-9 3.5.2 Enhanced Messages for MIMO on Uu Interface ................................................................ 3-10

4 Radio Bearers ............................................................................................................................4-1

5 TFRC.............................................................................................................................................5-1

6 Requirements of MIMO for RF Modules..............................................................................6-1

7 Performance Improvement in MIMO+HSDPA Scenario ..................................................7-1 7.1 Overview ....................................................................................................................................... 7-1 7.2 Virtual Antenna Mapping ............................................................................................................... 7-2 7.3 Intelligent Interference Control ...................................................................................................... 7-3

8 Parameters .................................................................................................................................8-1

9 Counters......................................................................................................................................9-1

10 Glossary ..................................................................................................................................10-1

11 Reference Documents .........................................................................................................11-1

WCDMA RAN MIMO 1 Introduction


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1 Introduction 1.1 Scope This document describes the MIMO (WRFD-010684 2×2 MIMO) features.

1.2 Intended Audience This document is intended for:

Personnel who are familiar with WCDMA basics Personnel who need to understand MIMO Personnel who work with Huawei products

1.3 Change History This section provides information on the changes in different document versions.

There are two types of changes, which are defined as follows:

Feature change: refers to the change in the MIMO feature. Editorial change: refers to the change in wording or the addition of the information that was not described in the earlier version.

Document Issues The document issues are as follows:

01 (2010-06-20)

01 (2010-06-20) This is the document for the first commercial release of RAN12.0. This is a new document.

WCDMA RAN MIMO 2 Overview of MIMO


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2 Overview of MIMO Multiple Input Multiple Output (MIMO) is an antenna technology for wireless communications in which multiple antennas are used at both the transmitter and the receiver. It can increase transmission rates through spatial multiplexing and improves channel qualities through space diversity without increasing transmit power and bandwidth.

HSPA+ uses 2x2 MIMO in the downlink to increase the single-user throughput and to improve the system capacity. 2x2 MIMO uses two antennas at the transmitter and two antennas at the receiver. The peak rate of 2x2 MIMO at the MAC layer can reach 28 Mbit/s.

2x2 MIMO is dependent on the HSDPA and Downlink Enhanced L2 features. That is, to use downlink MIMO, these two features must be activated. What’s more, the DC-HSDPA and MIMO cannot be concurrently used by one UE in 3GPP Release 8,.

2x2 MIMO requires support from the CN, RNC, NodeB, and UE. The requirements of 2x2 MIMO are listed in Table 2-1.

Table 2-1 Requirements of 2x2 MIMO

Item Requirement

CN The CN of 3GPP Release 6 supports 8 Mbit/s in the uplink and 16 Mbit/s in the downlink. To support the peak rate of 28 Mbit/s in downlink MIMO mode, the CN needs to support 3GPP Release 7.

RNC MIMO depends on HSDPA and Downlink Enhanced L2. Thus, the RNC needs to support HSDPA and Downlink Enhanced L2. In addition, the radio bearer scheme of MIMO is introduced.

NodeB MIMO depends on HSDPA and downlink enhanced L2. Thus, the NodeB needs to support HSDPA and downlink enhanced L2. MAC-ehs is a sub-function of Downlink Enhanced L2, which is responsible for scheduling and Transport Format and Resource Combination (TFRC) selection of MIMO. The cell needs to be configured with two TX antennas to support MIMO. The specific RF module configured with two TX antennas varies according to the model of the NodeB. For details, see 6 “Requirements of MIMO for RF Modules”. In addition, to perform channel estimation on each TX antennas, MIMO uses the pilot transmit diversity or the primary/secondary common pilot.

UE The UE must be of HS-DSCH category 15, 16, 17, 18, 19, or 20.

If the frequency resources are sufficient, the cells capable of only MIMO can be set up. In the initial phase of networking, MIMO and HSDPA usually co-exist in a cell to fully utilize frequency resources and to reduce network cost.

WCDMA RAN MIMO 3 Basic Principle


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3 Basic Principle 3.1 Overview The research on MIMO standardization started from 3GPP Release 5 and the following two standard schemes were finally defined in 3GPP Release 7:

Per-antenna rate control (PARC): The PARC architecture is motivated by an information theoretic result stating that the Shannon capacity limit for an open-loop MIMO link can be achieved. It is used for UTRA TDD.

Double Transmit antenna array (D-TxAA): D-TxAA is a MIMO scheme used for sending multiple data streams through spatial multiplexing. It is used for UTRA FDD.

This document mainly describes the MIMO scheme used for UTRA FDD. In UTRA FDD, the D-TxAA scheme usually adopts 2x2 MIMO which requires two TX antennas on the NodeB side and two RX antennas on the UE side.

Figure 3-1 shows the principle of 2x2 downlink MIMO.

Figure 3-1 Principle of 2x2 downlink MIMO

The NodeB MAC-ehs scheduler determines whether to transmit one or two transport blocks (TBs) in one TTI. In the case of two TBs, two streams can be transmitted simultaneously. They are called the primary stream (in blue) and the secondary stream (in red). The primary stream always exists, but the secondary stream may or may not exist, depending on channel conditions.

First, channel coding, spreading, and scrambling are performed on the TBs to obtain streams S1 and S2. These processes are the same as those in non-MIMO mode.

Then, MIMO precoding is performed on S1 and S2. The precoding is done to ensure the orthogonality of the two streams and thus reduce the interference between the two streams. The precoding follows the formula below.

In the formula, w1 to w4 represent four precoding weights. They are determined by the NodeB and UE during the process of channel estimation.

The UE estimates the channel quality for each antenna based on the pilot signals. The two TX antennas can transmit the same or different pilot signals by setting different pilot transmit modes. For details, see section 3.4 “Pilot Transmit Mode.”

3 Basic Principle WCDMA RAN

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According to the quality of received pilot signals, the UE reports the preferred precoding weight. The signaled information about the preferred precoding weight is termed precoding control indication (PCI). The PCI is signaled to the NodeB together with the channel quality indication (CQI) as a composite PCI/CQI report. The UE transmits the composite PCI/CQI report to the NodeB using the CQI field on the HS-DPCCH. Based on the composite PCI/CQI reports, the NodeB scheduler decides whether to schedule one or two transport blocks to the UE in one Transmission Time Interval (TTI) and also determines the transport block size(s) and modulation scheme(s) used for each of the transport blocks.

The same control channels are used in MIMO as before. However, the signaling carried on the control channels is different. The signaling formats on the HS-SCCH and HS-DPCCH are changed to process the following additional information required by MIMO:

Transport block (TB) sizes for each stream Modulation and coding scheme for each stream CQI for both antennas Antenna precoding weight reported or used More signaling sent to the UE to support dual-stream transmission More feedback received from the UE

Therefore, the HS-DPCCH frame format is optimized for MIMO, and a new HS-SCCH frame format, known as HS-SCCH type 3, is introduced. For detailed information, see sections 3.2 “HS-DPCCH Changed for MIMO” and 3.3 "HS-SCCH Type 3."

In addition, the messages over the Iub and Uu interfaces are enhanced to transfer MIMO-related information. For details, see section 3.5 "Enhanced Messages for MIMO."

3.2 HS-DPCCH Changed for MIMO 3.2.1 Overview For the UE not configured with MIMO, the HS-DPCCH needs to indicate only the ACK/NACK and CQI information about one stream. For the UE configured with MIMO, the channel coding for the HS-DPCCH is changed, and therefore the HS-DPCCH needs to indicate the ACK/NACK, PCI, and CQI information about a maximum of two streams.

Figure 3-2 shows the general coding flow in the case that the UE is configured in MIMO mode.

Figure 3-2 Coding flow for HS-DPCCH in the case that the UE is configured in MIMO mode



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As shown in Figure 3-2, the acknowledgement message is coded to 10 bits that are denoted w0, w1,…w9. The PCI and CQI information is coded to 19 bits that are denoted b0, b1,…b\19.

For detailed information about the channel coding for the HS-DPCCH, see section "Coding for HS-DPCCH" in 3GPP TS 25.212.

3.2.2 ACK Reporting In non-MIMO mode, the first slot of the HS-DPCCH subframe carries the feedback information (ACK or NACK). ACK/NACK indicates whether the downlink transport block is received successfully on the UE side.

In MIMO mode, if the NodeB MAC-ehs scheduler transmits one transport block (TB), the ACK/NACK is the same as that in non-MIMO mode. If the NodeB MAC-ehs scheduler transmits two TBs, the ACKs/NACKs for the two downlink TBs, that is, ACKs/NACKs of primary and secondary TBs, need to be transmitted in the first slot of the HS-DPCCH subframe.

Table 3-1 lists the information carried in the first slot of the HS-DPCCH subframe when the UE is configured in non-MIMO mode.

Table 3-1 Channel coding of HARQ-ACK when the UE is configured in non-MIMO mode

HARQ-ACK Message to Be Transmitted w0 w1 w2 w3 w4 w5 w6 w7 w8 w9

ACK 1 1 1 1 1 1 1 1 1 1

NACK 0 0 0 0 0 0 0 0 0 0

Table 3-2 lists the information carried in the first slot of the subframe of HS-DPCCH when the UE is configured in MIMO mode.

Table 3-2 Channel coding of HARQ-ACK when the UE is configured in MIMO mode

HARQ-ACK Message to Be Transmitted w0 w1 w2 w3 w4 w5 w6 w7 w8 w9

HARQ-ACK in response to a single scheduled transport block

ACK 1 1 1 1 1 1 1 1 1 1

NACK 0 0 0 0 0 0 0 0 0 0

HARQ-ACK in response to two scheduled transport blocks

Response to primary transport block

Response to secondary transport block

ACK ACK 1 0 1 0 1 1 1 1 0 1

ACK NACK 1 1 0 1 0 1 0 1 1 1

NACK ACK 0 1 1 1 1 0 1 0 1 1

NACK NACK 1 0 0 1 0 0 1 0 0 0


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The NodeB MAC-ehs scheduler determines whether to send new data or retransmit data according to the received feedback information.

For details, see section "Coding for HS-DPCCH" in 3GPP TS 25.212.

3.2.3 PCI Reporting In Figure 3-1, the primary stream (in blue) uses the weights w1 and w2, and the secondary stream (in red) uses the weights w3 and w4. These weights are defined as follows:

When w2 is determined, w1, w3, and w4 can all be determined according to the formulas. The UE estimates the value of w2 and reports it to the NodeB. w2 is indicated by the PCI and transmitted on the HS-DPCCH. After receiving the PCI from the UE, the NodeB determines the value of w2 and notifies the UE of the value through the HS-SCCH. w2 can be changed in each subframe of the HS-PDSCH.

The precoding weight w2 is mapped to PCI values as defined in Table 3-3.

Table 3-3 Mapping of preferred precoding weight w2 to PCI values

W2 PCI Value

(1+j)/2 00

(1-j)/2 01

(-1+j)/2 10

(-1-j)/2 11

PCI occupies two bits and is transmitted with CQI in the last two slots in each subframe of the HS-DPCCH.

For details about the PCI and precoding, see section "Precoding control indication (PCI) definition" in 3GPP TS 25.214.

3.2.4 CQI Reporting Both the single-stream CQI and the dual-stream CQI need to be reported. Because even when the channel conditions allow dual-stream transmission, the scheduler may use the single-stream transmission mode, for example, if there is only a small amount of data to be transmitted.

The UE reports type A CQIs and type B CQIs periodically to report single-stream CQIs and dual-stream CQIs.

Figure 3-3 shows an example of CQI reporting. In this example, the UE reports four type A CQIs and one type B CQI in each reporting period.



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Figure 3-3 An example of CQI reporting

Type A CQI and type B CQI are described as follows:

Type A CQI indicates the number (one or two) of transport blocks that can be transmitted simultaneously in a TTI and the transport format supported by each transport block.

Type B CQI indicates the transport format supported by a transport block.

Note that the dual-stream CQI is considered only in dual-stream transmission mode and the single-stream CQI is considered only in single-stream transmission. Though type A CQI can indicate a single-stream or dual-stream CQI, all type A CQIs reported by the UE may be dual-stream CQIs under favorable channel conditions. In this case, the NodeB depends only on type B CQI if it determines to use the single-stream transmission mode.

When the UE reports both types of CQI, the RAN obtains the complete channel condition information for single-stream transmission and dual-stream transmission. The RAN can then schedule a single stream or two streams as appropriate for the UE and the cell.

CQI Mapping Table After a service is set up on the HS-DSCH, the UE has to monitor the HS-SCCHs in each TTI and report CQIs periodically even if there is no data on the HS-DSCH.

The CQIs reported by UEs indicate channel conditions through CQI mapping tables. As shown in Table 3-4, the UEs of different categories have their respective CQI mapping tables.

Table 3-4 Applicability of CQI mapping tables

Used CQI Mapping Table

MIMO Not Configured MIMO Configured

64QAM Not Configured

64QAM Configured

Category

64QAM Not Configured

64QAM Configured

In Case of Type B or Single Transport Block Type A CQI Reports

In Case of Dual Transport Block Type A CQI Reports

In Case of Type B or Single Transport Block Type A CQI Reports

In Case of Dual Transport Block Type A CQI Reports

1-6 A N/A

7 and 8 B N/A

9 C N/A

10 D N/A

11 and 12 E N/A

13 C F N/A


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14 D G N/A

15 C N/A C H N/A

16 D N/A D I N/A

17 C F C H N/A

18 D G D I N/A

19 C F C H F J

20 D G D I G K

The CQI mapping tables are not described in this document. For details, see section 6A.2.3 "CQI tables" in 3GPP TS 25.214. Note that the transport block sizes corresponding to some CQIs in the CQI mapping tables are changed for better performance in Huawei implementation.

3.3 HS-SCCH Type 3 To implement downlink MIMO, a new HS-SCCH frame format, that is, HS-SCCH type 3, is introduced. The UE configured with MIMO uses only the HS-SCCH type 3 in either single-stream or dual-stream transmission mode.

The HS-SCCH type 3 is divided into part 1 and part 2. The two parts carry different information, which are described as follows:

Part 1 carries the channelization code set used by transport blocks, number of transport blocks, modulation schemes, and PCIs. The number of bits in part 1 and the meaning of each bit in dual-stream transmission mode are the same as those in single-stream transmission mode. In part 1, three bits are used to indicate the Modulation scheme and number of transport blocks information, as listed in Table 3-5.

Table 3-5 Modulation scheme and number of transport blocks information

Modulation Scheme Primary TB Secondary TB Number of TBs

111 16QAM 16QAM 2

110 16QAM QPSK 2

101 64QAM Indicated by the last bit of CCS

Indicated by the last bit of CCS

100 16QAM N/A 1

011 QPSK QPSK 2

010 64QAM 64QAM 2

001 64QAM 16QAM 2

000 QPSK N/A 1



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In Table 3-5, N/A means that the current transmission mode is single-stream mode, that is, there is no secondary transport block.

When the three bits are 101, the modulation scheme for the secondary transport block (TB) and the transmission mode are indicated by the last bit of Channelization-Code-Set (CCS): − If the last bit of CCS is 0, the number of TBs is 2 (that is, the transmission mode is dual-stream mode) and the modulation scheme for the secondary TB is QPSK.

− If the last bit of CCS is 1, the number of TBs is 1 (that is, the transmission mode is single-stream mode).

Based on such information, the UE knows whether the single-stream or dual-stream transmission mode is used.

Part 2 carries the transport block size, hybrid automatic retransmission request (HARQ) process information, redundancy and constellation version, and UE identity. In single-stream transmission mode, part 2 carries the process number, transport block size, and redundancy version of only the single stream. In dual-stream transmission mode, part 2 carries the process number of the primary stream that is configured by the higher layers. In addition, it carries the transport block sizes and redundancy versions of both the primary stream and the secondary stream. The process number of the secondary stream is calculated by the UE according to the process number of the primary stream as follows. (HAPpb + Nproc/2) mod (Nproc) Where, − HAPpb is the process number of the primary stream.

− Nproc is the number of HARQ processes configured by higher layers.

For details about the HS-SCCH type 3, see section "Coding for HS-SCCH type 3" in 3GPP TS 25.212.

3.4 Pilot Transmit Mode 3.4.1 Overview In a MIMO-capable cell, the UE configured with MIMO requires the pilot signal from the NodeB to estimate the channel conditions between multiple RX antennas and multiple TX antennas. The UE can estimate the channel conditions of each TX antenna in the following two modes:

Pilot transmit diversity mode In pilot transmit diversity mode, the pilot signals are carried on the P-CPICH and are transmitted through the two antenna ports. One antenna sends the modulation pattern of antenna port 1 of the P-CPICH. The other antenna sends the modulation pattern of antenna port 2 of the P-CPICH.

Primary/Secondary common Pilot (PSP) mode In the PSP mode, the pilot signals are carried on both P-CPICH and S-CPICH. One antenna sends the modulation pattern of antenna port 1 of the P-CPICH. The other antenna sends the modulation pattern of antenna port 1 of the S-CPICH.

In space time transmit diversity (STTD) mode, the receiver of a legacy HSDPA UE is degraded from an equalization receiver to a RAKE receiver, and thus the performance degrades significantly. Therefore, the PSP mode is recommended.


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3.4.2 Pilot Transmit Diversity In pilot transmit diversity mode, the signals on the SCH are transmitted from the two antennas in time switched transmit diversity (TSTD) mode. The HS-PDSCH and other channels in the cell are transmitted from the two antennas in STTD mode.

STTD can make full use of power. The total power allocated to each channel is the same as that collected in no-diversity cells. Assume that the TX power of a cell is 20 W, the power margin is 10% (2 W), the TX power of the P-CPICH is 1 W, and the TX power of the CCH is 1 W. Figure 3-4 shows the resource allocation between two antennas in pilot transmit diversity mode.

Figure 3-4 Resource allocation between two antennas in pilot transmit diversity mode

To enable the STTD mode of other channels, run the ADD UCELLSETUP command to set the cell as an STTD-supportive cell and set the transmit diversity mode of each channel to STTD. For the AICH, PICH, and S-CCPCH, run the ADD UAICH, ADD UPICH, and ADD USCCPCHBASIC commands to set the STTDInd parameter to TRUE.

3.4.3 Primary/Secondary common Pilot (PSP) In the Primary/Secondary common Pilot (PSP) mode, S-CPICH should be configured with the same power as PCPICH for channel estimation in the UE. In this mode, cell capacity is degraded because the available power is decreased, as shown in Figure 3-5. When only R5 HSDPA UEs and R99 UEs exist in the cell, PA1 and PA2 can be allocated only 5 W available power. That is, the power on the two PAs is unbalanced. To balance the power, the VAM technique is introduced. For details, see section 7.2 "Virtual Antenna Mapping."

Figure 3-5 Resource allocation between two antennas in PSP mode

To enable the PSP mode, run the ADD UPCPICH and ADD USCPICH commands.

In addition, in PSP mode under the scenario of MIMO with HSDPA, the MIMO signals and pilot signals carried on the S-CPICH might cause interference to HSDPA UEs that do not use MIMO, thus increasing



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the performance loss. To reduce such performance loss, the IIC technique can be used. For detailed information about IIC, see 7.3 "Intelligent Interference Control."

3.5 Enhanced Messages for MIMO 3.5.1 Enhanced Messages for MIMO on Iub Interface This section describes the enhanced messages for MIMO during the NodeB Application Part (NBAP) procedure. For detailed information, see 3GPP TS 25.433.

Resource Status Indication

The resource status indication procedure is followed by the NodeB to report the status of NodeB physical resources to the CRNC.

During the resource status indication procedure, if the local cell is MIMO-capable when it is set up, then the NodeB includes the MIMO Capability IE which is set to MIMO Capable for the local cell in the RESOURCE STATUS INDICATION message.

Audit Procedure

The audit procedure is followed by the CRNC. In this procedure, the configuration and status of the logical resources in the NodeB are audited, and for each MIMO-capable local cell, the NodeB includes the MIMO Capability IE that is set to MIMO Capable in the AUDIT RESPONSE message.

Cell Setup or Reconfiguration Procedure

During the cell setup or reconfiguration procedure, if the MIMO Pilot Configuration IE is included in the CELL SETUP REQUEST or CELL RECONFIGURATION REQUEST message, then the parameters defining the pilot configuration for MIMO are stored in the NodeB and applied when the MIMO mode is used.


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Radio Link Setup Procedure

During the radio link setup procedure, if the MIMO Activation Indicator IE is included in the HS-DSCH FDD Information IE in the RADIO LINK SETUP REQUEST message, then the NodeB activates the MIMO mode for the HS-DSCH Radio Link. In addition, the NodeB decides the UE reporting configuration (N/M ratio) for MIMO and includes the MIMO N/M Ratio IE in the HS-DSCH FDD Information Response IE in the RADIO LINK SETUP RESPONSE message. Moreover, the HARQ Memory Partitioning Information Extension for MIMO IE is included in the RADIO LINK SETUP RESPONSE message.

N/M ratio is used to indicate the reporting period of CQI type A/B.

Radio Link Addition Procedure

In this procedure, the MIMO-related elements are the same as those in the radio link setup procedure.

Synchronized Radio Link Reconfiguration Preparation Procedure

The synchronized radio link reconfiguration preparation procedure is followed to prepare a new configuration of radio link(s) related to a NodeB communication context.

In this procedure, the MIMO-related elements are the same as those in the radio link setup procedure.

3.5.2 Enhanced Messages for MIMO on Uu Interface This section describes the enhanced RRC signaling on the Uu interface, For detailed information, see 3GPP TS 25.331.

In the following Uu messages, the MIMO parameters IE is added to exchange the MIMO-related information:

ACTIVE SET UPDATE CELL UPDATE CONFIRM PHYSICAL CHANNEL RECONFIGURATION RADIO BEARER RECONFIGURATION



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RADIO BEARER RELEASE RADIO BEARER SETUP TRANSPORT CHANNEL RECONFIGURAITON

The MIMO parameters IE includes the following sub IEs:

MIMO operation: indicates the status of MIMO operation. MIMO N_cqi_type_A/M_cqi ratio: indicates the period for reporting the CQI type A/B. MIMO pilot configuration: indicates the pilot transmit mode and related configuration.

Moreover, in the PHYSICAL CHANNEL RECONFIGURATION message, the HARQ info IE is enhanced to indicate the number of HARQ processes for MIMO.

WCDMA RAN MIMO 4 Radio Bearers


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4 Radio Bearers During the service setup procedure for PS streaming service or PS BE service, downlink MIMO can be selected if the following conditions are met:

Downlink MIMO and downlink enhanced L2 are supported by the network and the UE, and both of them are activated. To activate downlink MIMO, select MIMO of the HspaPlusSwitch parameter, and CFG_HSDPA_MIMO_SWITCH of the CfgSwitch parameter. To activate downlink enhanced L2, select DL_L2ENHANCED of the HspaPlusSwitch parameter.

The downlink HS-DSCH and uplink E-DCH/DCH are selected as the transport channels. The MIMO64QAMorDCHSDPASwitch parameter is set to MIMO_64QAM, or DC-HSDPA is not activated.

The MIMOor64QAMSwitch parameter is set to MIMO, or 64QAM is not activated.

In the case of combined services, the bearer scheme for the service with the highest rate is used. For example, the combined services are VoIP service and BE service (384 kbit/s). If HS-SCCH Less Operation is applied to the VoIP service and MIMO is applied to the BE service, MIMO is applied to the combined service.

WCDMA RAN MIMO 5 TFRC


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5 TFRC For a UE with favorable channel conditions, adaptive modulation and coding (AMC) uses spatial multiplexing and dual-stream transmission to provide higher transmission rates. For a UE with unfavorable channel conditions, AMC uses transmit diversity and single-stream transmission to achieve higher transmission qualities.

In dual-stream transmission mode, transport format and resource combination (TFRC) selection is used to determine the TB size, transmit power for each stream in addition to the number of HS-PDSCH codes, the start codes, and the HS-SCCH codes shared by the two streams. In single-stream transmission mode, TFRC selection is the same as that in HSDPA.

In dual–stream transmission mode, TFRC is performed for each stream. The two streams use the same HS-PDSCH codes available.

The data of the UE is not scheduled or handled by TFRC before the NodeB receives the CQIs from the UE.

For details about TFRC, see the HSDPA Feature Parameter Description.

Selection of Single-Stream or Dual-Stream Transmission A UE configured with MIMO first attempts to use the dual-stream transmission mode because this mode brings MIMO gains and provides higher throughput for the UE.

The prerequisites for using the dual-stream transmission mode are as follows:

The UE reports dual-stream CQIs. A pair of HARQ process IDs meets the requirements of 3GPP TS 25.212. That is, the following formule must be met: HAPsb = (HAPpb + Nproc/2) mod (Nproc) Where: − HAPpb is the HARQ process ID of the primary stream. − HAPsb is the HARQ process ID of the secondary stream. − Nproc is the number of HARQ processes of the UE configured at higher layers. For details, see section 4.6B.2.5 "HARQ process identifier mapping" in 3GPP TS 25.212. The power allocated to each stream is not zero.

If the prerequisites are met, TFRC checks the traffic volume supported in dual-stream transmission mode and single–stream transmission mode. If more data can be transmitted in dual-stream transmission mode, this mode is configured.

In each TTI, the algorithm determines whether the conditions for using the dual-stream transmission mode are met. If the conditions are met, dual-stream transmission is performed in this TTI; otherwise, single-stream transmission is performed in this TTI.

For details about TFRC, see the HSDPA Feature Parameter Description.

WCDMA RAN MIMO 6 Requirements of MIMO for RF Modules


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6 Requirements of MIMO for RF Modules A cell needs to be configured with two TX antennas to support MIMO. The specific RF module configured for the 2x2 downlink MIMO mode varies according to the model of the NodeB. For details, see the NodeB Technical Description. Figure 6-1 and Figure 6-2 show examples of the hardware configuration of the NodeB in 2x2 downlink MIMO.

Figure 6-1 An example of the hardware configuration of the NodeB in 2x2 downlink MIMO (1)

(1) RF jumper (2) Inter-WRFU RF signal cable (3) CPRI cable

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Figure 6-2 An example of the hardware configuration of the NodeB in 2x2 downlink MIMO (2)

(1) RF jumper (2) CPRI optical cable

WCDMA RAN MIMO 7 Performance Improvement in MIMO+HSDPA Scenario


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7 Performance Improvement in MIMO+HSDPA Scenario This chapter mainly describes the feature WRFD-010700 Performace Improvement of MIMO and HSDPA Co-carrier.

7.1 Overview If the frequency resource is ample, the cells meant for only MIMO users can be set up. In the initial phase of networking, MIMO and HSDPA usually co-exist in a cell to save frequency resource and network cost. The recommended scenario of MIMO with HSDPA (MIMO+HSDPA) is shown in Figure 7-1.

Figure 7-1 Scenario of MIMO with HSDPA

As shown in Figure 7-1, assume that f1 carries an R99+HSDPA cell and f2 carries a MIMO+HSDPA cell. The pilot transmit mode of f2 is Primary/Secondary common Pilot (PSP) mode. The baseband output signals of the two cells are transmitted after being mapped to two PAs through virtual antenna mapping (VAM).

In this networking, the signals of MIMO and secondary CPICH have impact on non-MIMO HSDPA UEs and result in performance loss. Huawei introduces the intelligent interference control (IIC) technique to reduce such performance loss. IIC reduces the performance loss on non-MIMO HSDPA UEs using EQ receivers.

In conclusion, Huawei adopts the PSP, VAM and IIC techniques together to improve the performance of a MIMO+HSDPA cell. Figure 7-2 illustrates the position of each technique in the entire solution.

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Figure 7-2 Position of each technique in the entire solution

This section describes VAM and IIC. For details about PSP, see section 3.4.3 "Primary/Secondary common Pilot (PSP)."

7.2 Virtual Antenna Mapping Basic Principle The switch for this function is VAM.

Virtual antenna mapping (VAM) is used to balance the transmit power of two PAs and to maximize the power usage of two PAs. It is mainly used in the cell with PSP. Figure 7-3 shows the principle of VAM.

Figure 7-3 Principle of VAM in the scenario of MIMO with HSDPA

As shown in Figure 7-3, the data from virtual antenna 1 (V1) and virtual antenna 2 (V2) is evenly distributed to the two physical antennas through VAM transformation matrix and thus a balance is maintained between the TX power of the two physical antennas.

The VAM transformation matrix is as follows:

In the matrix form, the values of h1, h2, h3, and h4 are predefined so that P1 and P2 have almost the same effect.

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In a MIMO+HSDPA cell, the input data of V1 is the data from MIMO, CCH, R99 and HSDPA, and the input data of V2 is the data from MIMO. In an R99+HSDPA cell, the input data of V1 is the data from CCH, R99 and HSDPA, and there is no data input of V2.

PCI Codebook Restriction In the MIMO single-stream scenario, the power on the two physical antennas through VAM is related to the PCI values. The PCI values constantly change with the channel conditions and thus the output power of the two physical antennas is unbalanced. As a result, the peak-to-average power ratio (PAPR) of the PA might be extremely high. To solve this problem, the PCI codebook can be restricted. That is, the changes in PCI values and the consequent power imbalance can be reduced. This function restricts the MIMO single-stream PCI to {0, 3} and also adopts a specific form of VAM matrix to reduce the power imbalance and the PAPR.

The switch of the PCI codebook restriction function is PRECDWSRSW. If this switch is reset, it will take effect only after the cell is restarted.

7.3 Intelligent Interference Control The switch for this function is IICSW.

When the PSP mode is used, the signals transmitted through the secondary antenna are unknown to a legacy HSDPA UE. Therefore, the receiver of the legacy HSDPA UE does not suppress the multipath interference caused by these signals. As a result, the performance of legacy HSDPA services degrades. The IIC function smartly monitors the proportion of various users in a cell and dynamically allocates the total available power to MIMO users and HSDPA users. In this manner, the IIC function controls the interference of the signals transmitted through the secondary antenna on the HSDPA signals without deteriorating the HSDPA performance.

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8 Parameters Table 8-1 Parameter description

Parameter ID

NE MML Command Meaning

STTDInd BSC6900

ADD UAICH(Optional)

Meaning: This parameter indicates whether the SCCPCH shall use STTD or not. For detailed information of this parameter, refer to 3GPP 25.346. GUI Value Range: TRUE, FALSE Actual Value Range: TRUE, FALSE Unit: None Default Value: False

STTDInd BSC6900

ADD UPICH(Optional)


STTDInd BSC6900

ADD USCCPCHBASIC(Optional)


HspaPlusSwitch

BSC6900

ADD UCELLALGOSWITCH(Optional)

Meaning: This parameter is used to select a feature related to HSPA+. If a feature is selected, it indicates that the corresponding algorithm is enabled. If a feature is not selected, it indicates that the corresponding algorithm is disabled. Note that other factors such as license and the physical capability of NodeB restrict whether a feature can be used even if this feature is selected. The EFACH/MIMO switch determines whether the cell supports the E-FACH/MIMO feature but does not affect the establishment of the E-FACH and the MIMO cell. GUI Value Range: 64QAM(Cell 64QAM Function Switch), MIMO(Cell MIMO Function Switch), E_FACH(Cell E_FACH Function Switch), DTX_DRX(Cell DTX_DRX Function Switch), HS_SCCH_LESS_OPERATION(Cell HS_SCCH LESS OPERATION Function Switch), DL_L2ENHANCED(Cell DL L2ENHANCED Function Switch), 64QAM_MIMO(Cell 64QAM+MIMO Function Switch), UL_16QAM(Cell UL 16QAM Function

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Parameter NE MML Command Meaning ID

Switch), DC_HSDPA(Cell DC-HSDPA Function Switch), UL_L2ENHANCED(Cell UL L2ENHANCED Function Switch) Actual Value Range: 64QAM, MIMO, E_FACH, DTX_DRX, HS_SCCH_LESS_OPERATION, DL_L2ENHANCED, 64QAM_MIMO, UL_16QAM, DC_HSDPA, UL_L2ENHANCED Unit: None Default Value: None

CfgSwitch BSC6900

SET UCORRMALGOSWITCH(Optional)

Meaning: Channel configuration strategy switch group. 1) CFG_DL_BLIND_DETECTION_SWITCH: When the switch is on, the DL blind transport format detection function is used for single SRB and AMR+SRB bearers. Note that the UE is only required to support the blind transport format stipulated in 3GPP 25.212 section 4.3.1. 2) CFG_HSDPA_64QAM_SWITCH: When the switch is on, 64QAM can be configured for the HSDPA service. 3) CFG_HSDPA_DC_SWITCH: When the switch is on, DC can be configured for the HSDPA service. 4) CFG_HSDPA_MIMO_SWITCH: When the switch is on, MIMO can be configured for the HSDPA service. 5) CFG_HSDPA_MIMO_WITH_64QAM_SWITCH: When the switch is on and the switches for 64QAM and MIMO are on, 64QAM+MIMO can be configured for the HSDPA service 6) CFG_HSPA_DTX_DRX_SWITCH: When the switch is on, DTX_DRX can be configured for the HSPA service. 7) CFG_HSPA_HSSCCH_LESS_OP_SWITCH: When the switch is on, HS-SCCH Less Operation can be configured for the HSPA service. 8) CFG_HSUPA_16QAM_SWITCH: When the switch is on, 16QAM can be configured for the HSUPA service. 9) CFG_IMS_SUPPORT_SWITCH: When the switch is on and the IMS license is activated, the RNC supports IMS signaling. 10) CFG_LOSSLESS_DLRLC_PDUSIZECHG_SWITCH: When the switch is on, DL lossless RLC PDU size change is supported. 11) CFG_LOSSLESS_RELOC_CFG_SWITCH: When the switch is on and the UE supports lossless relocation, the RNC configures lossless relocation for PDCP parameters if the requirements of RLC mode, discard mode, and sequential submission are met. Then, lossless relocation is used for the UE. 12) CFG_MULTI_RAB_SWITCH: When the switch is on, the RNC supports multi-RABs combinations such

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as 2CS, 2CS+1PS, 1CS+2PS, and 2PS. 13) CFG_PDCP_IPV6_HEAD_COMPRESS_SWITCH: When the switch is on and the PDCP header compression license is activated, the PDCP header compression algorithm for IPv6 is used at the RNC. 14) CFG_PDCP_RFC2507_HC_SWITCH: When the switch is on and the PDCP IPHC license is activated, the PDCP IPHC header compression algorithm is used for the RNC. 15) CFG_PDCP_RFC3095_HC_SWITCH: When the switch is on and the PDCP ROHC license is activated, the PDCP ROHC header compression algorithm is used for the RNC. 16) CFG_PTT_SWITCH: When this switch is on, the RNC identifies the PTT user based on the QoS attributes in the RAB assignment request message. Then, the PTT users are subject to special processing. 17) CFG_RAB_REL_RMV_HSPAPLUS_SWITCH: When this switch is on and if an RAB release is performed, the RNC decides whether to fall back a certain HSPA(HSPA+) feature based on the requirement of remaining traffic carried by the UE. That is, if an HSPA+ feature is required by the previously released RAB connection but is not required in the initial bearer policy of the remaining traffic, the RNC falls back the feature to save the transmission resources. The HSPA+ features that support the fallback are MIMO, 64QAM, MIMO+64QAM, UL 16QAM, DC-HSDPA, and UL TTI 2ms. GUI Value Range: CFG_DL_BLIND_DETECTION_SWITCH, CFG_HSDPA_64QAM_SWITCH, CFG_HSDPA_DC_SWITCH, CFG_HSDPA_MIMO_SWITCH, CFG_HSDPA_MIMO_WITH_64QAM_SWITCH, CFG_HSPA_DTX_DRX_SWITCH, CFG_HSPA_HSSCCH_LESS_OP_SWITCH, CFG_HSUPA_16QAM_SWITCH, CFG_IMS_SUPPORT_SWITCH, CFG_LOSSLESS_DLRLC_PDUSIZECHG_SWITCH, CFG_LOSSLESS_RELOC_CFG_SWITCH, CFG_MULTI_RAB_SWITCH, CFG_PDCP_IPV6_HEAD_COMPRESS_SWITCH, CFG_PDCP_RFC2507_HC_SWITCH, CFG_PDCP_RFC3095_HC_SWITCH, CFG_PTT_SWITCH, CFG_RAB_REL_RMV_HSPAPLUS_SWITCH Actual Value Range: CFG_DL_BLIND_DETECTION_SWITCH,

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CFG_HSDPA_64QAM_SWITCH, CFG_HSDPA_DC_SWITCH, CFG_HSDPA_MIMO_SWITCH, CFG_HSDPA_MIMO_WITH_64QAM_SWITCH, CFG_HSPA_DTX_DRX_SWITCH, CFG_HSPA_HSSCCH_LESS_OP_SWITCH, CFG_HSUPA_16QAM_SWITCH, CFG_IMS_SUPPORT_SWITCH, CFG_LOSSLESS_DLRLC_PDUSIZECHG_SWITCH, CFG_LOSSLESS_RELOC_CFG_SWITCH, CFG_MULTI_RAB_SWITCH, CFG_PDCP_IPV6_HEAD_COMPRESS_SWITCH, CFG_PDCP_RFC2507_HC_SWITCH, CFG_PDCP_RFC3095_HC_SWITCH, CFG_PTT_SWITCH, CFG_RAB_REL_RMV_HSPAPLUS_SWITCH Unit: None Default Value: None

MIMOor64QAMSwitch

BSC6900

SET UFRC(Optional)

Meaning: According to the R8 protocol, MIMO and 64QAM can be used together. When the condition is not met, for example the cell does not support the features, MIMO may be not used together with 64QAM. In this case, "MIMOor64QAMSwitch" is used to determine whether MIMO or 64QAM is preferentially used. GUI Value Range: MIMO, 64QAM Actual Value Range: MIMO, 64QAM Unit: None Default Value: MIMO

VAM NodeB ADD LOCELL(Optional)

Meaning: Supoport VAM or not GUI Value Range: FALSE(False), TRUE(True) Actual Value Range: FALSE, TRUE Unit: None Default Value: False

PRECDWSRSW

NodeB MOD LOCELL(Optional) ADD LOCELL(Optional)

Meaning: Precoding Weight Set Restriction Switch GUI Value Range: FALSE(False), TRUE(True) Actual Value Range: FALSE, TRUE Unit: None Default Value: -

IICSW NodeB SET MACHSPARA(Optional)

Meaning: IIC Switch GUI Value Range: OPEN(Open), CLOSE(Close) Actual Value Range: OPEN, CLOSE Unit: None Default Value: -

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9 Counters For details, see the BSC6900 UMTS Performance Counter Reference and the NodeB Performance Counter Reference.

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10 Glossary For the acronyms, abbreviations, terms, and definitions, see the Glossary.

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11 Reference Documents [1] HSDPA Feature Parameter Description

[2] Directed Retry Decision Feature Parameter Description

[3] Glossary

MIMO

Documents

happb nproc2

primarysecondary

composite

preferred

ehs scheduler

transport

downlink enhanced

wcdma ran