LTE - Aperiodic CSI

 

The purpose of this tutorial is to show you how to configure Aperiodic CQI report in LTE for single carrier and multi carrier environment.  When mutiple carriers are being used (especially the number of component carrier is large), to perform the measurement and report for every cell at every reporting occasion can be a big overhead. Aperiodic trigger is a mechanism by which you can select a specific cells to make the report. eNB can define a table with multiple rows in which a specific combination of component carriers for the report are defined in the form of a bitmap. Each of the rows in the table is called 'trigger' in RRC message. Once this trigger is configured, eNB can select a specific trigger when it sends DCI to request aperiodic report.

Overall procedure / mechanism for Aperiodic CSI report can be summarized as follows :

Step 1 : eNB configures the requirement (e.g, type of report item (CQI, PMI, RI) and the list of cells to report) for the report in RRC message

Step 2 : eNB triggers the report using DCI 0 when it wants the report (in DCI, eNB configure the field 'csi_request' to tell UE to perform the report as specified in RRC message)

Step 3 : UE perform the measurement and send the report via PUSCH

 

 

Table of Contents

• LTE - Aperiodic CSI
• Test Setup
• Key Configuration Parameters
• Test 1 : 1 CC
• Configuration
• Perform the Test
• Log Analysis
• Test 2 : 2CC CA - with Aperiodic CQI
• Configuration
• Perform the Test
• Log Analysis
• Sub Test 1 : 2 Trigger - Same
• Sub Test 2 : 2 Trigger - Different
• Test 3 : 6CC CA - with Aperiodic CQI
• Configuration
• Perform the Test
• Log Analysis
• Sub Test 1 : 6 Trigger - 2 CCs per Trigger
• Sub Test 2 : 6 Trigger - Arbitrary CCs per Trigger
• RRC / NAS Signaling
• RrcConnectionReconfiguration
• FAQ

 

 

Test Setup

Test setup for this tutorial is as shown below. In this setup, it shows 4 SDR cards are connected with Antenna but not all the test in this tuturial requires the 4 sdr cards. You only have to connect antenna to the number of sdr cards that you need for each test.

 

 

Key Configuration Parameters

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

• scell_list: In this link, you will get the descriptions for all the items listed below.
• cell_id
• cross_carrier_scheduling
• scheduling_cell_id
• ul_allowed
• rrc_configuration
• individual_offset
• ap_cqi_period
• ap_cqi_trigger_list
• ap_cqi_rm
• ap_cqi_rm_opt

 

 

Test 1 : 1 CC

This test configures 1 LTE Cell with the configuration of Aperiodic CQI Report

 

Configuration

In this test, I used enb_1cc_ap_cqi.cfg without modification.

I used the mme-ims.cfg config as it is.

The configuration in enb_1cc_ap_cqi.cfg  is as shown below.  

In this test, only one cell is configured in cell_list and you don't need any specific configuration here. Just set whatever frequency and band that your DUT supports.

In cell default configuration, periodic CSI report is disabled by setting cqi_period and m_ri to 0. And Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm.

 

Perform the Test

Check out cell configuration with 'cell phy' and 'cell' command and make it sure that all the cells are configured as intended.

NOTE : you may not always see the print for CC=1 because the print shown here is a sampled / averaged.  You may take it as success as long as you see the print for CC = 2.

 

Log Analysis

Sample Log

Check out the cqi report is enabled or disabled as intended by checking out physicalConfigDedicated in RRC connection Reconfiguration message.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Serving cell. (Check out this note to figure out how csi_request value is translated to trigger number)

Check out the triggered Apperiodic report by checking PUSCH with csi rpoert(ri, cqi).

 

 

Test 2 : 2CC CA - with Aperiodic CQI

This test configures 2 cells as follows.

• 2 LTE FDD Cells

It performs following procedure

Step 1 : Initial Attach to LTE

Step 2 : Establish 2CC CA in LTE with Aperiodic CQI

 

Configuration

In this test I used the enb-2cc-ap-cqi-trigger.cfg which is copied and modified from enb-2cc.cfg

Followings are the configurations in enb-2cc-ap-cqi-trigger.cfg

Set CQI_CONFIG 1 to enable Aperiodic CSI Report.

In this test, only two cell are configured in cell_list for carrier aggregation. So each of the cell has scell_list in the configuration that specifies all the other cells as SCC(Secondary Component Carrier).

This is the configuration for the first cell (cell_id 1), so the 2nd cell(cell_id 2) is registered in scell_list

This is the configuration for the 2ndcell (cell_id 2), so the 1st cell(cell_id 1) is registered in scell_list

In cell default configuration, periodic CSI report is disabled by skipping cqi_period and m_ri setting. And Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, csi trigger is not configured indicating that the default trigger setting will be applied.

 

Perform the Test

Check out cell configuration with 'cell phy' and 'cell' command and make it sure that all the cells are configured as intended.

NOTE : you may not always see the print for CC=1 because the print shown here is a sampled / averaged.  You may take it as success as long as you see the print for CC = 2.

 

Log Analysis

Sample Log

Check out Aperiodic Trigger setting in RRC Connection Reconfiguration. Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Check if Carrier Aggregation is established as intended by checking out sCellToAddModList in Rrc Connection Reconfiguration message.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out this note to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

Sub Test 1 : 2 Trigger - Same

In this sub test, I will show you an example of setting two triggers of same configuration.

In cell default configuration, periodic CSI report is disabled by skipping cqi_period and m_ri setting. And Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, ap cqi trigger is configured by setting ap_cqi_trigger_list.

 

Sample Log

Check out Aperiodic Trigger setting in RRC Connection Reconfiguration. Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Check if the carrier aggregation is configured as intended by checking out sCellToAddModList IE in RRC Connection Reconfiguration message.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out this note to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. The value in binary indicates the trigger number configured in RRC. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 2. (Check out this note to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

Sub Test 2 : 2 Trigger - Different

In this sub test, I will show you an example of setting two triggers with different configuration for each trigger.

In cell default configuration, periodic CSI report is disabled by skipping cqi_period and m_ri setting. And Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, ap cqi trigger is configured by setting ap_cqi_trigger_list.

 

Sample Log

Check out Aperiodic Trigger setting in RRC Connection Reconfiguration. Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Check if the carrier aggregation is configured as intended by checking out sCellToAddModList IE in RRC Connection Reconfiguration message.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out this note to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 2. (Check out this note to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

Test 3 : 6CC CA - with Aperiodic CQI

This test configures 6 cells as follows.

• 6 LTE FDD Cells

It performs following procedure

Step 1 : Initial Attach to LTE

Step 2 : Establish 6CC CA in LTE with Aperiodic CQI

 

 

Configuration

In this test I used the enb-6cc-ap-cqi.cfg which is copied and modified from gnb-nsa.cfg

Followings are the configurations in enb-6cc-ap-cqi.cfg

NOTE : This test is using 6 LTE Carriers. so make it sure that you have enough number of SDR cards that can be allocated for 6 carriers.

In this test, 6 cells are configured in cell_list for carrier aggregation. So each of the cell has scell_list in the configuration that specifies all the other cells as SCC(Secondary Component Carrier).

This is the configuration of the first cell(cell_id 1), so cell_id 2,3,4,5,6 are registered in scell_list

This is the configuration of the seond cell(cell_id 2), so cell_id 1,3,4,5,6 are registered in scell_list

This is the configuration of the 3rd cell(cell_id 3), so cell_id 1,2,4,5,6 are registered in scell_list

This is the configuration of the 4th cell(cell_id 4), so cell_id 1,2,3,5,6 are registered in scell_list

This is the configuration of the 5th cell(cell_id 5), so cell_id 1,2,3,4,6 are registered in scell_list

This is the configuration of the 6th cell(cell_id 6), so cell_id 1,2,3,4,5 are registered in scell_list

In cell default configuration, periodic CSI report is disabled by skipping cqi_period and m_ri setting. And Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, ap cqi trigger is configured by setting ap_cqi_trigger_list. In this test, ap_cqi_trigger_list is not configured which mean that the default configuration will be applied.

 

Perform the Test

Check out cell configuration with 'cell phy' and 'cell' command and make it sure that all the cells are configured as intended. In this test, make it sure that all of the 6 cells (carriers) are configured as intended.

NOTE : you may or may not see the print for C=1 (i.e, the connected state before establising carrier aggregation) because the print shown here is a sampled / averaged.  You may take it as success as long as you see the print for C = 6.

 

Log Analysis

Sample Log

In the log, check out how the aperiodic trigger list are configured in RRC and then how each of the items in the trigger list are used in DCI 0.  Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Following logs shows how DCI 0 utilize the configured trigger list. In Amarisoft eNB, it uses each triggers in round-robin manner. (NOTE : only the triggers whicn is NOT ALL-ZERO are used).

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 2. (Check out  FAQto figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

Sub Test 1 : 6 Trigger - 2 CCs per Trigger

In this sub test, I will show you an example of setting 6 triggers with different configuration for each cells and each triggers has two component carriers enabled.

In this test I used the enb-6cc-ap-cqi_trigger_2perTrigger.cfg which is copied and modified from gnb-nsa.cfg

In  enb-6cc-ap-cqi_trigger_2perTrigger.cfg, aperiodic triggers are configured as follows.

In cell default configuration,  Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, ap cqi trigger is configured by setting ap_cqi_trigger_list. Here you see 6 triggers are configured and each of the trigger has two component carries enabled.

 

In the log, check out how the aperiodic trigger list are configured in RRC and then how each of the items in the trigger list are used in DCI 0.   Sample Log

Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Following logs shows how DCI 0 utilize the configured trigger list. In Amarisoft eNB, it uses each triggers in round-robin manner. (NOTE : only the triggers whicn is NOT ALL-ZERO are used)

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 2. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 3. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 4. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 5. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 6. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

Sub Test 2 : 6 Trigger - Arbitrary CCs per Trigger

In this sub test, I will show you an example of setting 6 triggers with different configuration for each cells and each triggers has different number of component carriers enabled.

In this test I used the enb-6cc-ap-cqi_trigger_arbTrigger.cfg.cfg which is copied and modified from gnb-nsa.cfg

In enb-6cc-ap-cqi_trigger_arbTrigger.cfg.cfg , aperiodic cqi is configured as follows.

In cell default configuration,  Aperiodic CSI report is enabled by configuring ap_cqi_period and ap_cqi_rm. In this test, ap cqi trigger is configured by setting ap_cqi_trigger_list. Here you see 6 triggers are configured and each of the trigger has different number of component carries enabled.

 

In the log, check out how the aperiodic trigger list are configured in RRC and then how each of the items in the trigger list are used in DCI 0.  Sample Log

Convert the Hex number of each trigger in aperiodicCSI-Trigger IE into binary and you would figure out the trigger settings for each CC (Component Carrier).

Following logs shows how DCI 0 utilize the configured trigger list. In Amarisoft eNB, it uses each triggers in round-robin manner. (NOTE : only the triggers whicn is NOT ALL-ZERO are used)

This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 1. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 2. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 3. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 4. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 5. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

Find a DCI 0 with csi_request set to Non-zero value. This triggers UE to send PUSCH with Aperiodic CQI report. Here it request CSI report configured by Trigger 6. (Check out FAQ to figure out how csi_request value is translated to trigger number)

Find the PUSCH that carries CSI report (ri, cqi) that are requested by the DCI.

 

 

RRC / NAS Signaling

 

RrcConnectionReconfiguration

: This is the RrcConnectionReconfigurationmessage sent by eNB  to configure Aperiodic Trigger (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 {

        '270FDC9A170107420......08'H

      },

      radioResourceConfigDedicated {

        srb-ToAddModList {

          {

            srb-Identity 2,

            rlc-Config explicitValue: am: {

              ul-AM-RLC {

                t-PollRetransmit ms60,

                pollPDU pInfinity,

                pollByte kBinfinity,

                maxRetxThreshold t32

              },

              dl-AM-RLC {

                t-Reordering ms45,

                t-StatusProhibit ms0

              }

            },

            logicalChannelConfig defaultValue: NULL

          }

        },

        drb-ToAddModList {

          {

            eps-BearerIdentity 5,

            drb-Identity 1,

            pdcp-Config {

              discardTimer infinity,

              rlc-AM {

                statusReportRequired TRUE

              },

              headerCompression notUsed: NULL

            },

            rlc-Config am: {

              ul-AM-RLC {

                t-PollRetransmit ms80,

                pollPDU p64,

                pollByte kB125,

                maxRetxThreshold t32

              },

              dl-AM-RLC {

                t-Reordering ms35,

                t-StatusProhibit ms10

              }

            },

            logicalChannelIdentity 3,

            logicalChannelConfig {

              ul-SpecificParameters {

                priority 15,

                prioritisedBitRate kBps8,

                bucketSizeDuration ms100,

                logicalChannelGroup 3

              }

            }

          }

        },

        physicalConfigDedicated {

          cqi-ReportConfig-r10 {

            cqi-ReportAperiodic-r10 setup: {

              cqi-ReportModeAperiodic-r10 rm30,

              aperiodicCSI-Trigger-r10 {

                trigger1-r10 'C0'H,

                trigger2-r10 '40'H

              }

            },

            nomPDSCH-RS-EPRE-Offset 0,

            cqi-ReportPeriodic-r10 release: NULL

          },

          pucch-ConfigDedicated-v1020 {

            pucch-Format-r10 channelSelection-r10: {

              n1PUCCH-AN-CS-r10 setup: {

                n1PUCCH-AN-CS-List-r10 {

                  {

                    0,

                    1,

                    2,

                    3

                  }

                }

              }

            }

          },

          cqi-ReportConfigPCell-v1250 {

            altCQI-Table-r12 allSubframes

          }

        }

      },

      nonCriticalExtension {

        nonCriticalExtension {

          nonCriticalExtension {

            sCellToAddModList-r10 {

              {

                sCellIndex-r10 1,

                cellIdentification-r10 {

                  physCellId-r10 2,

                  dl-CarrierFreq-r10 1575

                },

                radioResourceConfigCommonSCell-r10 {

                  nonUL-Configuration-r10 {

                    dl-Bandwidth-r10 n25,

                    antennaInfoCommon-r10 {

                      antennaPortsCount an1

                    },

                    phich-Config-r10 {

                      phich-Duration normal,

                      phich-Resource one

                    },

                    pdsch-ConfigCommon-r10 {

                      referenceSignalPower -29,

                      p-b 0

                    }

                  }

                },

                radioResourceConfigDedicatedSCell-r10 {

                  physicalConfigDedicatedSCell-r10 {

                    nonUL-Configuration-r10 {

                      antennaInfo-r10 {

                        transmissionMode-r10 tm1,

                        ue-TransmitAntennaSelection release: NULL

                      },

                      crossCarrierSchedulingConfig-r10 {

                        schedulingCellInfo-r10 own-r10: {

                          cif-Presence-r10 FALSE

                        }

                      },

                      pdsch-ConfigDedicated-r10 {

                        p-a dB0

                      }

                    },

                    ul-Configuration-r10 {

                      cqi-ReportConfigSCell-r10 {

                        cqi-ReportModeAperiodic-r10 rm30,

                        nomPDSCH-RS-EPRE-Offset-r10 0,

                        cqi-ReportPeriodicSCell-r10 release: NULL

                      }

                    },

                    cqi-ReportConfigSCell-v1250 {

                      altCQI-Table-r12 allSubframes

                    }

                  }

                }

              }

            }

          }

        }

      }

    }

  }

}

 

 

FAQ

 

[Q1]  How can I interpret the ap_cqi_trigger_list[] in the configuration file and how it gets translated to RRC Configuration ?

[A1] Explained below.

 

This configuration is translated to RRC configuration as follows.

 

[Q2]  How each of the trigger is selected by each triggering DCI 0 ?

[A2] The trigger is selected in round robin manner among the triggers which are NOT all 0.

hopping_flag=0

riv=0x451

mcs1=29

new_data_indicator1=0

tpc_command=0

cyclic_shift=0

csi_request=<"Value of CSI request field" of the Table 7.2.1-XX in 36.213>    

rb_alloc_type=0

In case of 6CC as an example, the maning of csi_request value indicates differently depending on which specific 7.2.1-XX table is applied. The table selection algorithm is described in 36.213-7.2.1 which is very confusing. For the current Amarisoft configuration, you may assume that 7.2.1-1D is used. Given that, you can interpret the value of csi_request as follows :