Fad Rrmtele TX Mode Mimo

LTE Radio Access, Rel. RL50, Operating Documentation, Issue 01

Transmission Modes/MIMO DN0943929 Issue 04A Approval Date 2013-09-23 Confidential

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Transmission Modes/MIMO

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Table of contents This document has 24 pages. Summary of changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1

Introduction to Transmission Modes/MIMO functionalities . . . . . . . . . . . 7

2 2.1 2.2

Transmission Modes/MIMO features. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Functional overview of LTE69: Transmit Diversity for Two Antennas . . . 9 Functional overview of LTE70: Downlink Adaptive Open Loop MIMO for Two Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3 2.4 2.5

Functional overview of LTE187: Single TX path mode . . . . . . . . . . . . . 10 Functional overview of LTE703: DL adaptive closed loop MIMO for two antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Functional overview of LTE568: DL Adaptive Closed Loop MIMO (4x2) 10

2.6 2.7

Functional overview of LTE980: IRC for 4 RX Paths. . . . . . . . . . . . . . . 11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3

Architecture of the MIMO control functional area. . . . . . . . . . . . . . . . . . 12

4 4.1 4.2

Functional description for Transmission Modes/MIMO . . . . . . . . . . . . . 13 MIMO principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Downlink MIMO Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.3 4.4 4.5

Single antenna port transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Multi antenna port transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 MIMO Switching Concepts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.5.1 4.5.2

Dynamic Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Fast Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5

Management data related to Transmission Modes/MIMO. . . . . . . . . . . 24

5.1

5.3

Management data for LTE69: Transmit Diversity for Two Antennas and LTE70: Downlink Adaptive open Loop MIMO for Two Antennas. . . . . . 24 Management data for LTE703: DL adaptive closed loop MIMO for two antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Management data for LTE568: DL Adaptive Closed Loop MIMO (4x2) 24

5.4

Management data for LTE980: IRC for 4 RX Paths. . . . . . . . . . . . . . . . 24

5.2

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List of figures

4

Figure 1

MIMO control within the LTE RRM architecture . . . . . . . . . . . . . . . . . . . 12

Figure 2 Figure 3 Figure 4

MIMO classification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 MIMO principle with 2x2 antenna configuration . . . . . . . . . . . . . . . . . . . 14 2x2 MIMO configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


Transmission on a single antenna port. . . . . . . . . . . . . . . . . . . . . . . . . . 17 Transmit diversity example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 TxDiv with two antenna ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18


Open Loop Spatial Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Closed loop single stream downlink transmit diversity . . . . . . . . . . . . . . 19 Closed loop spatial multiplexing dual stream . . . . . . . . . . . . . . . . . . . . . 20

Figure 11 Figure 12

Dynamic MIMO mode switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Dynamic MIMO Mode Control Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 22


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List of tables

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Table 1

Multi antenna options in LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2 Table 3 Table 4

Transmission Modes/MIMO features . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Transmission modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 dlMimoMode parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 5

Possible configuration for transmission modes deliverd from dlMimoMode 17


5

Summary of changes


Summary of changes Changes between issues 04 DRAFT (2013-06-20, RL50) and 04A (2013-09-23, RL50) Transmission Modes/MIMO features (2) •

•

Functional overview of LTE70: Downlink Adaptive Open Loop MIMO for Two Antennas has been updated. Functional overview of LTE703: DL Adaptive Closed Loop MIMO for Two Antennas has been updated.

Downlink MIMO Mode (4.2) •

Table 4 dlMimoMode parameter has been updated.

•

The Open loop spatial multiplexing (OL SM) section has been updated.

•

The MIMO Switching Concepts (4.5) chapter has been added.

Changes between issues 03 (2011-06-17, RL40) and 04 DRAFT (2013-06-20, RL50) Introduction to Transmission Modes/MIMO functionalities (1) •

Chapter has been updated.

Transmission Modes/MIMO features (2) •

The LTE568: DL Adaptive Closed Loop MIMO (4x2) feature has been added.

•

The LTE980: IRC for 4 RX Paths feature has been added.

MIMO principles (4.1) •

Chapter has been updated.

Downlink MIMO Mode (4.2) •

Range of the

dlMimoMode parameter

has been updated.

Fast Adaptive Closed Loop MIMO (4.6) •

Chapter has been added.

Changes between issues 02 (2010-12-10) and 03 (2011-06-17) Introduction to Transmission Modes/MIMO functionalities (1) •

Functions that are not supported in RL30 have been removed.

Functional overview of LTE69: Transmit Diversity for Two Antennas (2.1) •

Information about PVS for synchronization signals has been added.

Summary (2.5) •

Redundant information has been removed.

Functional description for Transmission Modes/MIMO (4) •

Whole chapter has been rewritten.

Measurements and counters for Transmission Modes/MIMO •

Chapter has been removed.

Management data related to Transmission Modes/MIMO (5) •

6

Chapter has been added.

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Introduction to Transmission Modes/MIMO functionalities

1 Introduction to Transmission Modes/MIMO functionalities In conventional wireless communications, a single antenna is used at the source, and another single antenna is used at the destination. In some cases, this gives rise to problems with multipath effects. When an electromagnetic f ield encounters obstructions such as hills, canyons, buildings, and utility wire s, the wavefronts are scattered, and thus they take many paths to reach the destination. The late arrival of scattered portions of the signal causes problems such as fading, cut-out (cliff effect), and intermittent reception (picket fencing). In digital communications systems such as wireless Internet, this can cause a reduction in data speed and an increase in the number of errors. The use of two or more antennas, along with the transmission of multiple signals (one for each antenna) at the source and the destination, eliminates the trouble caused by multipath wave propagation, and can even take advantage of this effect. MIMO (multiple input, multiple output) is an antenna technology for wireless communications in which multiple antennas are used at both the source (transmitter) and the destination (receiver). The antennas at each end of the communications circuit are combined to minimize errors and optimize data speed. Multiple input multiple output (MIMO) is an emerging technology to me et the demand for higher data rate and better cell coverage even without increasing the average transmit power or frequency bandwidth. The MIMO structure successfully constructs multiple spatial layers where multiple data streams are delivered on a given frequency-time resource and linearly increases the channel capacity. Multiple input multiple output (MIMO) technologies introduced in LTE, such as spatial multiplexing, transmit diversity, and beamforming are key components to improve the downlink peak rate, cell coverage, as well as the average cell throughput. In general, the transmission and reception modes can be classified by the terms SISO (Single Input Single Output), SIMO (Singl e Input Multiple Output), MISO (Multiple Input Single Output), and MIMO (Multiple Input M ultiple Output). The term SISO refers to the basic technology without profiting from signal path diversity. The MIMO technology combines transmit and receive diversity. For “open loop MIMO”, no UE feedback concerning precoding is required. This technology is c omplemented by “closed loop MIMO”, where a codebook based precoding scheme is used. MIMO refers to the use of multiple antennas at the transmitter and at the receiver. For the LTE downlink, a 2x2 configuration for MIMO is assumed as the baseline configuration, for example two transmit antennas at the base station and two re ceive antennas at the terminal side. Different gains can be achieved depending on the MIMO mode that is used. The following table gives an overview on the typical LTE multi antenna configurations:

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Introduction to Transmission Modes/MIMO functionalities


DL BS

UE

TX

RX

1x2 1

2

2x2 2

2

UL

Gain to smaller configuration

+ 4 ... 5 dB DL link budget

UE

BS

TX

RX

Gain to smaller configuration

Configuration type

1x2 1

2

minimum

1x2 1

2

standard

1x4 1

4

+ 100% peak data rate + user experience + 10% spectrum efficiency 4x2 4

2

+ 3 ... 4 dB DL link budget + moderate capacity gains

+ 3 ... 4 dB UL link budget

high-performance

+ user experience + up to 50% spectrum efficiency

Table 1

8

Multi antenna options in LTE

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Transmission Modes/MIMO features

2 Transmission Modes/MIMO features Table 2 shows all features related to MIMO per release. Features

Related documents

Release

LTE187: Single TX Path Mode

this document

RL10

LTE69: Transmit diversity for two antennas

this document

RL10

LTE70: Downlink Adaptive Open Loop MIMO for Two Antennas

this document

RL10

LTE703: DL Adaptive Closed Loop MIMO for Two Antennas

see LTE703: DL adaptive closed loop MIMO for two antennas

RL20

LTE568: DL Adaptive Closed Loop MIMO (4x2)

see LTE568: DL Adaptive Closed Loop MIMO (4x2)

RL50

LTE980: IRC for 4 RX Paths

see LTE980: IRC for 4 RX Paths RL50

Table 2


2.1

Functional overview of LTE69: Transmit Diversity for Two Antennas The eNB transmits single data stream via 2 TX diversity paths. Sp ace-Frequency Block Code (SFBC) mode is applied. Single data stream is transmitted through two diversity antennas per sector.Transmit diversity mode is applicable for most physical downlink channels with the following exceptions: •

•

Synchronization signals are transmitted via the first TX antenna or Precoding Vector Switching (PVS) scheme. eNB sends different cell-specific reference signals per antenna. The operator can enable the semi-static transmit diversity mode on cell basis by the O&M configuration.

Transmit diversity for two antennas enhances cell coverage and capacity.

2.2

Functional overview of LTE70: Downlink Adaptive Open Loop MIMO for Two Antennas The eNB selects dynamically between TX diversity (SFBC) and open loop spatial multiplexing with Large Delay Cyclic Delay Diversity (LD CDD). The open loop adaptive MIMO for two antennas allows dynamic switching between transmit diversity (SFBC) using one codeword and open loop spatial multiplexing with two layers and two codewords. The open loop dynamic MIMO switch functionality can b e enabled/disabled on cell level by means of O&M. When the dynamic MIMO switch is disabled too, either static spatial multiplexing or static transmit diversity can be selected for the whole cell (all UEs). The dynamic switch takes into account t he UE specific link quality and rank information.

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A settable O&M threshold on cell level for the link quality is provided. The UE radio capabilities are considered. Outer loop CQI conpensation is provided to keep the target BLER. A performance counter for the transmission mode usage is supported per cel l. The adaptive algorithm combines the gain of high peak rates (two code words) and good cell edge performance (single code word).

2.3

Functional overview of LTE187: Single TX path mode The TX signal is transmitted through a single TX antenna per cell, either due to HW configuration or in semi-static mode selected by O&M in case of HW configuration with two TX paths per cell The single TX path mode can be applied in two scenarios dependent on HW configuration of the eNB: •

•

HW configuration with only one TX path per cell HW configuration with two TX paths per cell but the second TX path is disabled through O&Mconfiguration

The latter scenario is primarily intended for trialing purposes. In this case, the same 2path HW configuration supports enhanced operational modes of TX diversity or MIMO. The operator can select the TX mode semi-statically on cell basis through O&M configuration.The single TX path per cell mode is the most basic transmit solution without spatial diversity in the eNB. A single patte rn of symbols for cell-specific Reference signal (RS) is sent in downlink direction. In uplink direction, two RX paths per cell is always supported by the eNB.

2.4

Functional overview of LTE703: DL adaptive closed loop MIMO for two antennas The closed loop adaptive spatial multiplexing for two antennas allows dynamic switching between a transmission with one code word and a transmission with two code words in downlink for single user MIMO. Further details on the related layer mapping can be found in TS 36.211. Spatial multiplexing is applied only to the PDSCH. Pre-coding is done according to the codebook described in TS 36.211. The switching point between the two transmission modes is operator configurable per cell. The LTE703: DL adaptive closed loop MIMO for two antennas feature is ASW.

2.5

Functional overview of LTE568: DL Adaptive Closed Loop MIMO (4x2) The LTE568: DL Adaptive Closed Loop MIMO (4x2) feature extends the already existing MIMO functionality to support precoding for spatial multiplexing for two antenna ports (MIMO 2x2) to be extended to four antenna ports (MIMO 4x2) at the eNB side in DL direction. CL MIMO (4x2) leads to improved cell capacity (average cell throughput) and coverage at the cell edge.

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2.6


Functional overview of LTE980: IRC for 4 RX Paths IRC is an equalizer used for diversity combining. The LTE980: IRC for 4 RX Paths feature combines the received signal in such a way that the overall post-equalizer signal to interference and noise ratio is maximized. IRC is an extension to 4-way RX diversity and Maximum Ratio Combining (MRC), (for more information, see LTE72: 4-way RX diversity). IRC equalizer has already been implemented for 2 RX (for more information, see LTE979: IRC for 2 RX paths).

2.7

Summary By means of the feature LTE70: Downlink adaptive open loop MIMO for two antennas, the eNodeB is able to select dynamically between Space Frequency Block Coding (SFBC) Transmit Diversity and Open Loop Spatial Multiplexing with Large-delay Cyclic Delay D iversity (Large-delay CDD). Using the feature LTE69: Transmit diversity for two antennas , the eNodeB transmits each data stream via 2 TX diversity paths. Each data stream is transmitted by two diversity antennas per sector, and “Space Frequency Block Coding (SFBC) Transmit Diversity” is applied. Diversity methods complement the basic feature LTE187: Single TX path mode , where the TX signal is transmitted via a single TX antenna per cell. With the feature LTE703:DL adaptive closed loop MIMO for two antennas , spatial multiplexing mode can be selected dynamically while applying closed loop MIMO for two antennas. The adaptive algorithm provide s the gain of high peak rates (two code words) and good cell edge performance (single code word). In addition to the LTE703:DL adaptive closed loop MIMO for two antennas feature, the LTE568: DL Adaptive Closed Loop MIMO (4x2) feature is introduced. It extends already implemented solution to four antenna ports. When this feature is configured, the eNB supports improved codebook with respect to corresponding precoding used for MIMO 2x2 (16 PMIs instead of 4 for layer 1 and 2 for layer 2 tran smissions). More PMIs means that there are more cases for precoding for 4 Tx antennas compared to 2 Tx antennas.

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Architecture of the MIMO control functional area


3 Architecture of the MIMO control functional area MIMO control is a part of radio resource management and telecom mainly concent rated in the layers 1 and 2 regarding the OSI reference model. It i s handled in the eNodeB and the UE in the radio access part of the LTE network. The following figure shows how MIMO control is located in the LTE RRM architecture:

Figure 1

12

MIMO control within the LTE RRM architecture

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Functional description for Transmission Modes/MIMO

4 Functional description for Transmission Modes/MIMO 4.1

MIMO principles MIMO is an antenna technology for wireless communications in which multiple antennas are used at both the source (transmitter) and the destination (receiver).

Figure 2

MIMO classification

The antennas at each end of the communications circuit are combined to minimize errors and optimize data speed. Figure 2 MIMO classification shows three main areas in which MIMO can be considered.

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Up to 4x2 antenna configuration is supported. The b asic mechanism of MIMO processing is presented on the Figure 3 MIMO principle with 2x2 antenna configuration. The baseband signal representing a downlink physical channels consists of the following steps (3GPP 36.211): •

•

•

scrambling of coded bits in each of the code words to be transmitted on a physical channel modulation of scrambled bits mapping of the complex-valued modulation symbols onto one or several transmission layers

•

precoding on each layer for transmission on the antenna ports

•

OFDM signal generation for each antenna port

Figure 3

MIMO principle with 2x2 antenna configuration

A spatial layer is the term which defines different streams generated by spatial multiplexing. A layer is described as mapping of symbols onto the transmit antenna ports. Example of MIMO transmission

Figure 4 2x2 MIMO configuration shows dual code word 2x2 SU-MIMO Spatial Multiplexing. The two base station transmit signals, two UE receive signals, and four channels form (for each subcarrier) a system of two equations with two unknown transmit signals. The two unknown transmit signals can be reconstructed by channel estimation, the possible transmit alphabet(s), and the two receive signals.

Figure 4

2x2 MIMO configuration

Transmission of two independent data streams transmitted at the same time depends on the channels’ signal quality and the decorrelation of both channels.

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4.2


Downlink MIMO Mode Transmission modes

The eNB selects the optimum MIMO mode and precoding configuration. The information is transmitted to the UE as part of DCI (downlink control information) on PDCCH. DCI format 2 means a downlink assignment o f two code words including precoding information. DCI format 2a is used with open l oop spatial multiplexing. DCI format 1b provides a downlink assignment of one code word including precoding information. Table 3 Transmission modes shows all transmission modes which are defined by 3GPP with supported DCI formats and UE feedback information. Mode

PDSCH transmission scheme

DCI formats

DCI includes

UE feedback

1

Single Antenna, port 0

1

Transport Block 1 Information

CQI

2

Transmit Diversity

1


CQI

3

Open Loop Spatial Multiplexing

2A

Transport Block 1 and 2 Information, Pre-coding Information

CQI, Ri

4

Closed Loop Spatial Multiplexing

2


CQI, Ri, PMI

5

MU-MIMO (not supported yet)

1D


CQI, PMI

6

Closed Loop Spatial Multiplexing using Single Transmission Layer (not supported yet)

1B


CQI, PMI

7

Single Antenna Port, port 5 (supported only in time division duplex)

1


CQI

8

Dual layer transmission, port 7 and 8 (supported only in time division duplex)

2B


CQI

Table 3

Transmission modes

PDCCH format 1A is the only fo rmat being received even by UEs not conf igured with a transmission mode, see 3GPP TS36. 213, section 7.1. Therefore, PDCCH format 1A is used for the resource allocation due to random access message 4 before the LBTS can rely at least on the default transmission formats depending on antenna configuration according to 3GPP TS36.331, section 9.2.3.

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dlMimoMode

The O&M parameter dlMimoMode is for cell-specific downlink adjustment of the transmission mode. This parameter is available only if at least two transmit antennas are in cell. dlMimoMode

0

Description Single Stream Downlink (SingleTx)

All downlink physical channels are transmitted using this mode 1

Single Stream Downlink Transmit Diversity (TxDiv)

All downlink physical channels are transmitted using TM2. 2

Single Stream Downlink Transmit Diversity for four Tx antennas (4-way TxDiv)

All downlink physical channels are transmitted using TM2. 4-way TxDiv must not be configured in dual band configurations. 3

Dual Stream MIMO Spatial Multiplexing (Static Open Loop MIMO)

SRB1 (DCCH) and RBs (DTCH) on PDSCH are transmitted using Dual Stream MIMO with spatial multiplexing; SRB0 (CCCH), BCCH and PCCH on PDSCH and all other physical channels are transmitted usin g Single Stream Downlink Transmit Diversity 4

Dynamic Open Loop MIMO

SRB1 (DCCH) and RBs (DTCH) on PDSCH are transmitted using either Single Stream Downlink Transmit Diversity or Dual Stream MIMO with spatial multiplexing depending on radio conditions; SRB0 (CCCH), BCCH and PCCH on PDSCH and all other physical channels are transmitted using Single Stream Downlink Transmit Diversity 5

Dynamic Closed Loop MIMO

SRB1 (DCCH) and RBs (DTCH) on PDSCH are transmitted using either Single Stream Downlink Transmit Diversity or Single or Dual Stream MIMO with Closed Loop spatial multiplexing depending on radio conditions and UE category; S RB0 (CCCH), BCCH and PCCH on PDSCH and all other physical channels are transmitted using Single Stream Downlink Transmit Diversity 6

Closed Loop MIMO (4x2)

SRB1 (DCCH) and RBs (DTCH) on PDSCH are transmitted using either Single Stream Downlink Transmit Diversity or Single or Dual Stream MIMO with Closed Loop spatial multiplexing depending on radio conditions and UE category; S RB0 (CCCH), BCCH and PCCH on PDSCH and all other physical channels are transmitted using Single Stream Downlink Transmit Diversity. Table 4

16

dlMimoMode parameter


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Possible configurations

The O&M configuration for control and common channels is static per cell. It is passed at system start or in case of O&M database changes to the lower layers, that is TUP L1/L2. Currently, in the cell all common and control channels are commanded with the same L1/L2 configuration, which is automatically derived from dlMimoMode parameter. Table 5 Possible configuration for transmission modes deliverd from dlMimoMode presents the configuration of common and control channels and also synchronization signals. Precoding vector switching 3GPP transmission mode

Single Tx

TxDiv

Dual Stream Dual Stream Open Loop SM Closed Loop SM

1

2

3

4

SynchroniPSS zation signal SSS

+

+

-

-

-

+

+

-

-

-

Control Channels

PBCH

-

+

+

-

-

PDCCH

-

+

+

-

-

PHICH

-

+

+

-

-

PCFICH

-

+

+

-

-

PDSCH

-

+

+

+

+

Data Channel

Reference signals

Using antenna port 0 for Single Tx. Using antenna port 0 and 1 in all other cases

Table 5

Possible configuration for transmission modes deliverd from dlMimoMode

4.3

Single antenna port transmission In the single antenna port transmission there is no MIMO.

Figure 5

4.4

Transmission on a single antenna port

Multi antenna port transmission Transmit diversity

Four-branch transmit diversity is supported. It is based on SFBC (Space Frequency Block Coding). SFBC is a frequency domain version of well-known Alamouti codes.

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These codes are designed so that the transmitted diversity streams are orthogonal and achieve the optimal SNR with a linear receiver. If the total eNB transmit power keeps the transmit power per transmit branch a s high as for the single transmit antenna case, the link budget is increased by 3 dB for two branches and by 6 dB for four branches. This implies coverage and capacity enhancements. If the total eNB transmit power is constant (compared to the single transmit branch case), transmit diversity leads to mo re robust links at the cell edge while slightly reducing cell capacity. However, for DRX VoIP users, tran smit diversity (TxDiv) slightly enhances cell capacity by approximately 5% for two transmit branches. Figure 6 Transmit diversity example shows the example of transmit diversity usag e which increases robustness and enhances cell edge performance.

Figure 6

Transmit diversity example

Transmit diversity can be semi-statically configured per cell, while for non-MIMO UEs, dlMimoMode =1 for PDSCH is automatically selected. It uses Rank 1 transmission that is no multiplication of data rates. Figure 7 TxDiv with two antenna ports presents the TxDiv working scheme.

Figure 7

TxDiv with two antenna ports

In case of transmit diversity mode, only one code word can be transmitted. Each antenna transmits the same information stream, but with different coding.

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Open loop spatial multiplexing (OL SM)

SM allows to transmit different streams of data simultaneously on the same resource blocks. SM increases the data rate and the overall capacity. In LTE spatial multiplexing, up to two code wo rds can be mapped onto different spatial layers. One code word represents an output from the channel code r. More details about the mapping of code words onto layers is specified in 3GPP TS 36.211 Physical Channels and Modulation. Figure 8 Open Loop Spatial Multiplexing illustrates how OL SM is done.

Figure 8

Open Loop Spatial Multiplexing

Closed loop rank 1 precoding

Closed loop (CL) spatial multiplexing (Figure 9 Closed loop single stream downlink transmit diversity) uses precoding from a defined codebook to form the transmitted layers. The UE feeds back to t he eNB the most desirable entry from a predefined codebook, that is Precoding Matrix Indicator ( PMI ). The best precoder is the martix distributing the layers between the antenna ports, which maximizes the capacity based on the the estimation of the channel matrix.

Figure 9

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Closed loop single stream downlink transmit diversity


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Closed loop spatial multiplexing dual stream

In the closed loop SM transmission the eNB decid es about PMI that is used in downlink and it is either the reported value from UE or another/default PMI, as soon as the eNB overrides the reported UE proposal. Figure 10 Closed loop spatial multiplexing dual stream shows CL SM dual stream, where the eNB transmits two individual streams to the UE. In this case the UE sends to eNB not only CQI and RI, but also preferred PMI.

Figure 10

4.5 4.5.1

Closed loop spatial multiplexing dual stream

MIMO Switching Concepts Dynamic Switch Dynamic MIMO mode switching depends on radio conditions. The eNB switches between TxDiv and SM, or CL SM single stream and dual stream (depending on tx Mimo mode). Class 1 UEs, which are not DL MIMO capable always use the diversity m ode, independently of that MIMO SM has been statically assigned or the dynamic OL/CL SM algorithm was enabled by the operator. Consequently, the dynamic MIMO Mode Control (MC) algorithm does not apply to non-MIMO UEs. Figure 11 Dynamic MIMO mode switching presents the moment, when MIMO-MC algorithm switches the UE from SM to TxDiv.

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Figure 11


Dynamic MIMO mode switching

Algorithm

The eNB’s decision on the MIMO mode of a certain UE is based on the filtered RANK and normalized, compensated, and filtered CQI measurements. The eNB remembers the last selected MIMO mode (either OL diversity/CL single codeword transmission abbreviated as DIV_1CW or OL SM/CL double codeword transmission abbreviated as SM_2CW). For more details on MIMO-MC algorithm, see LTE70: Downlink adaptive open loop MIMO for two antennas and LTE703: DL adaptive closed loop MIMO for two antennas. Figure 12 Dynamic MIMO Mode Control Algorithm shows the flow diagram for dow nlink dynamic MIMO Mode switching.

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Figure 12

4.5.2


Dynamic MIMO Mode Control Algorithm

Fast Switch In addition to dynamic MIMO mode switching, the fast adap tive MIMO switching is supported. Fast adaptive MIMO switching enables fast Rank selection and fast codebook-

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based precoding of data transmission, using CL feedback of PMI in combination with RI (for more information, see LTE568: DL Adaptive Closed Loop MIMO (4x2)).

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Management data related to Transmission Modes/MIMO


5 Management data related to Transmission Modes/MIMO This section lists management data related Transmission Modes/MIMO per feature.

5.1

Management data for LTE69: Transmit Diversity for Two Antennas and LTE70: Downlink Adaptive open Loop MIMO for Two Antennas LTE69: Transmit Diversity for Two Antenn as and LTE70: Downlink Adaptive open Loop MIMO for Two Antennas.

5.2

Management data for LTE703: DL adaptive closed loop MIMO for two antennas LTE703: DL adaptive closed loop MIMO for two antennas .

5.3

Management data for LTE568: DL Adaptive Closed Loop MIMO (4x2) LTE568: DL Adaptive Closed Loop MIMO (4x2)

5.4

Management data for LTE980: IRC for 4 RX Paths LTE980: IRC for 4 RX Paths

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Id:0900d805809ecaec Confidential

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Fad Rrmtele TX Mode Mimo

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