LTE TM(Transmission Mode)

 

The purpose of this tutorial is to show you how to configure various TM(Transmission Mode). Main focus in this tutorial is to show how the parameters in the configuration is reflected to RRC message and how to verify the operation with CSI message and DCI.

Transmission Mode in LTE is a configuration that determines the transmission mode for eNB antenna. For example, let's assume that an eNB is using 2 TX antenna. With this two antenna, eNB can implement various different transmission scheme as listed below.

• Tx Diversity
• Open Loop 2x2 MIMO (2x2 MIMO that does not require CSI report from UE)
• Closed Loop 2x2 MIMO (2x2 MIMO that requires CSI report from UE for proper precoding matrix selection)

Each of these use case (implementation) is called 'Transmission Mode'. Then the question arises on how UE can figure out what kind of transmission mode that eNB applies ?  This is done by RRC parameters sent by eNB which informs on the details of transmission mode.  As of now, there are 10 different transmission mode (TM1 ~ TM10) defined in 3GPP specification and this tutorial would covers some of the transmission mode that are relatively widely used or tested.

 

 

Table of Contents

• LTE TM(Transmission Mode)
• Test Setup
• Key Configuration Parameters
• Test 1 :  TM3 - 2x2 MIMO
• Configuration
• Run and Check
• Log Analysis
• Test 2 :  TM4 - 2x2 MIMO
• Configuration
• Run and Check
• Log Analysis
• Test 3 :  TM3 - 4x4 MIMO
• Configuration
• Run and Check
• Log Analysis
• Test 4 :  TM4 - 4x4 MIMO
• Configuration
• Run and Check
• Log Analysis
• Test 5 :  TM4 - 4x4 MIMO, Codebook Subset Restriction
• Configuration
• Run and Check
• Log Analysis
• Test 6 :  TM9 - 2x2 MIMO, Periodic CSI Report
• Configuration
• Run and Check
• Log Analysis
• Test 7 :  TM9 - 2x2 MIMO, Aperiodic CQI Report
• Configuration
• Run and Check
• Log Analysis
• Test 8 :  TM10 - 2x2 MIMO, Periodic CSI Report
• Configuration
• Run and Check
• Log Analysis
• RRC / NAS Signaling
• RrcConnectionReconfiguration

 

 

Test Setup

 

Test setup for this tutorial is as shown below.

• SIM Card used in this tutorial is the one delivered with the system as it is.
• If you want to change the configuration, The tutorial Configuration Guide would help

 

 

Key Configuration Parameters

Followings are important configuration parameters for this tutorial. You may click on the items for the descriptions from Amarisoft documents.

• n_antenna_dl
• transmission_mode
• transmission_mode_opt
• codebook_subset_restriction
• codebook_subset_restriction_opt
• n_scid
• ue_specific_port
• csi_rs_nzp
• csi_rs_zp
• ap_cqi_period
• ap_cqi_rm
• ap_cqi_rm_opt

 

 

Test 1 :  TM3 - 2x2 MIMO

This test is to show how to configure TM3 (Transmission Mode 3) with 2x2 MIMO and test it.

 

Configuration

I used the eNB configuration enb-tm3-2x2.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm3-2x2.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 2 for 2x2 MIMO and set TM to 3 for Transmission Mode 3.

Set configure the parameter transmission_mode with TM you defined before. In most of sample configuration, this parameter would be set with a specific hardcoded number. But I used a predefined constant in this test just to make the configuration easier.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out UE capability information and ensure that the UE supports MIMO and TM as you intended to configure.

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig is set as you intended to configure.

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.

 

 

Test 2 :  TM4 - 2x2 MIMO

This test is to show how to configure TM4 (Transmission Mode 4) with 2x2 MIMO and test it.

 

Configuration

I used the eNB configuration enb-tm4-2x2.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm4-2x2.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 2 for 2x2 MIMO and set TM to 4 for Transmission Mode 4.

Set configure the parameter transmission_mode with TM you defined before. In most of sample configuration, this parameter would be set with a specific hardcoded number. But I used a predefined constant in this test just to make the configuration easier.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out UE capability information and ensure that the UE supports MIMO and TM as you intended to configure.

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig is set as you intended to configure.

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.

 

 

Test 3 :  TM3 - 4x4 MIMO

This test is to show how to configure TM3 (Transmission Mode 3) with 4x4 MIMO and test it.

 

Configuration

I used the eNB configuration enb-tm3-4x4.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm3-4x4.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 4 for 4x4 MIMO and set TM to 3 for Transmission Mode 3.

Set configure the parameter transmission_mode with TM you defined before. In most of sample configuration, this parameter would be set with a specific hardcoded number. But I used a predefined constant in this test just to make the configuration easier.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out UE capability information and ensure that the UE supports MIMO and TM as you intended to configure.

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig is set as you intended to configure.

In case of 4x4, you should see that maxLayerMIMO is set to fourLayers.

 

 

Test 4 :  TM4 - 4x4 MIMO

This test is to show how to configure TM4 (Transmission Mode 4) with 4x4 MIMO and test it.

 

Configuration

I used the eNB configuration enb-tm4-4x4.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm4-4x4.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 4 for 4x4 MIMO and set TM to 4 for Transmission Mode 4.

Set configure the parameter transmission_mode with TM you defined before. In most of sample configuration, this parameter would be set with a specific hardcoded number. But I used a predefined constant in this test just to make the configuration easier.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out UE capability information and ensure that the UE supports MIMO and TM as you intended to configure.

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig is set as you intended to configure.

In case of 4x4 MIMO, you should see maxLayerMIMO is set to fourLayers.

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.

 

 

Test 5 :  TM4 - 4x4 MIMO, Codebook Subset Restriction

This test is to show how to configure TM4 (Transmission Mode 4) with 4x4 MIMO and codebook subset restriction and test it.

 

Configuration

I used the eNB configuration enb-tm4-4x4-Codebook.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm4-4x4-Codebook.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 4 for 4x4 MIMO and set TM to 4 for Transmission Mode 4 and define CODEBOOK_SUBSET as you like.

Set configure the parameter transmission_mode with TM you defined before. In most of sample configuration, this parameter would be set with a specific hardcoded number. But I used a predefined constant in this test just to make the configuration easier.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out UE capability information and ensure that the UE supports MIMO and TM as you intended to configure.

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode , codebookSubsetRestriction  and cqi-ReportConfig is set as you intended to configure.

In case of 4x4 MIMO, you should see that maxLayersMIMO is set to fourLayers.

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.

 

 

Test 6 :  TM9 - 2x2 MIMO, Periodic CSI Report

This test is to show how to configure TM9 (Transmission Mode 9) with 2x2 MIMO and Periodic CSI Report and test it.

 

Configuration

I used the eNB configuration enb-tm9-2x2.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm9-2x2.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 2 for 2x2 MIMO and I set TDD 1 to configure the cell for TDD.

transmission_mode is hardcoded to 3 and transmission_mode_opt is set to 9. Set the parameters codebook_subset_restriction_opt, n_scid, ue_specific_port as you want.

Configure csi_rs_nzp and csi_rs_zp as you want for the test.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig and csi-RS-Config are set as you intended to configure.

It is not mandatory, but you may filter physical channels that you want for easy analysis (In this case, DCCH, PDCCH,PDSCH,PUSCH are selected for display)

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.  For TM9, DCI format 2c is used.

 

 

Test 7 :  TM9 - 2x2 MIMO, Aperiodic CQI Report

This test is to show how to configure TM9 (Transmission Mode 9) with 2x2 MIMO and Aperiodic CQI Report and test it.

 

Configuration

I used the eNB configuration enb-tm9-2x2-ap.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm9-2x2-ap.cfg , the configurations are set as follows.

Set N_ANTENNA_DL to 2 for 2x2 MIMO and I set TDD 1 to configure the cell for TDD.

Set cqi_period to 0 to disable periodic CQI. Set ap_cqi_period, ap_cqi_rm, ap_cqi_rm_opt to enable aperiodic CQI report.  transmission_mode is hardcoded to 3 and transmission_mode_opt is set to 9. Set the parameters codebook_subset_restriction_opt, n_scid, ue_specific_port as you want.

Configure csi_rs_nzp and csi_rs_zp as you want for the test.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig and csi-RS-Config are set as you intended to configure.

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.  For TM9, dci format 2c is used and for aperiodic CSI report the dci 0(UL grant) should set csi_request to 1.

For aperiodic CQI report, UE is reporting CQI via PUSCH (not PUCCH)

 

 

Test 8 :  TM10 - 2x2 MIMO, Periodic CSI Report

This test is to show how to configure TM10 (Transmission Mode 10) with 2x2 MIMO and Periodic CSI Report and test it.

 

Configuration

I used the eNB configuration enb-tm10-2x2.cfg which is copied from enb.default.cfg and modified for this tutorial.

I used the mme configuration mme-ims.cfg and ims configuration ims.default.cfg

 

In enb-tm10-2x2.cfg , the configurations are set as follows.

 

Run and Check

Check the cell phy configuration and see if it is configured as intended.

run 't' command and power on UE and make it sure that UE complete the attach.

 

Log Analysis

Sample Log

Check out physicalConfigDedicated IE in RRC Connection and ensure that transmissionMode and cqi-ReportConfig and csi-RS-Config are set as you intended to configure.

Check out transmission mode and cqi-ReportConfig and ensure that they are configured as intended.

It is not mandatory, but you may filter physical channels that you want for easy analysis (In this case, DCCH, PDCCH,PDSCH,PUSCH are selected for display)

Check out DCI to ensure MIMO scheduling and check out PUCCH format to ensure that eNB is getting the report as expected.  For TM10, dci format 2d is used

 

 

RRC / NAS Signaling

 

RrcConnectionReconfiguration

: This is the RrcConnectionReconfigurationmessage sent by eNB  to configure Transmission Mode. (NOTE : You would see some IEs that has a specific assigned vale here, but consider it as just an example value. Those values should vary depending on test requirement)

 

{

  message c1: rrcConnectionReconfiguration: {

    rrc-TransactionIdentifier 0,

    criticalExtensions c1: rrcConnectionReconfiguration-r8: {

      dedicatedInfoNASList {

        '...'H

      },

      radioResourceConfigDedicated {

        srb-ToAddModList {

          ...

        },

        physicalConfigDedicated {

          antennaInfo-r10 explicitValue-r10: {

            transmissionMode-r10 tm4,

            codebookSubsetRestriction-r10 '0001AAABFFFFFFFF'H,

            ue-TransmitAntennaSelection release: NULL

          },

          cqi-ReportConfig-r10 {

           ...

          },

          cqi-ReportConfigPCell-v1250 {

            ...

          }

        },

        drb-ToAddModList-r15 {

          {

            ...

          }

        }

      },