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LTE Handover Events, Measurement Reports

prodevelopertutorial September 7, 2020

In this chapter we shall learn about

1. RSRP and RSRQ
2. Handover events
3. Introduction to handover.

RSRP:

Reference Signal Receive Power.

It is the average power of Resource Element that carry cell specific Reference Signal.

 

RSRQ:

Reference Signal Received Quality

Both of the above parameters are used for cell selection, re-selection and handover.

2. Handover events

LTE Measurement Reporting Events (A1, A2, A3, A4, A5, A6, B1, B2)

A1 : Serving becomes better than threshold. It will release the measurement gap.

A2 : Serving becomes worse than threshold. It will setup measurement gap.

A3 : Neighbour becomes offset better than serving. It will trigger Intra-LTE handover

A4 : Neighbour becomes better than threshold.

A5 : Serving becomes worse than threshold1 and neighbour becomes better than threshold2. It will trigger Inter-RAT measurement events

B1 : Inter RAT neighbour becomes better than threshold.

B2 : Serving becomes worse than threshold1 and inter RAT neighbour becomes better than threshold2. It will trigger Inter-RAT handover

 

3. Introduction to handover.

For eNB to make handover decision, UE has to send some measurement reports in order to know if the target cell is suitable to camped on.

This procedure is called as “Measurement Procedure”. The below image shows you the “Measurement Procedure.”

measurement_report

eNB will send RRC Connection Reconfiguration message that consist of parameters related to one or more events.

Then if any of the specific event is satisfied, then only UE will send the measurement report to eNB.

Measurement Configuration details sent by RRC Connection Reconfiguration request message

Measurement Objects: The objects that UE will perform measurements.

Reporting Configurations:

Reporting criteria: Criteria that will trigger the UE to send a measurement report.

Reporting format: Quantities that the UE includes in the measurement report and associated information.

Measurement identities

Quantity configurations

Measurement gaps

 

RRC Connection Reconfiguration message

rrcConnectionReconfiguration-r8
    measConfig
        measObjectToAddModList: 2 items
            Item 0
                MeasObjectToAddMod
                    measObjectId: 1
                        measObject: measObjectEUTRA (0)
                            measObjectEUTRA
                                carrierFreq: 2175
                                allowedMeasBandwidth: mbw50 (3)
                                .... 0... presenceAntennaPort1: False
                                neighCellConfig: No MBSFN subframes are present in all neighbour cells (1)
                                offsetFreq: dB0 (15)
            Item 1
                MeasObjectToAddMod
                    measObjectId: 2
                        measObject: measObjectEUTRA (0)
                            measObjectEUTRA
                                carrierFreq: 5790
                                allowedMeasBandwidth: mbw50 (3)
                                .... ..0. presenceAntennaPort1: False
                                neighCellConfig: No MBSFN subframes are present in all neighbour cells (1)
                                offsetFreq: dB0 (15)
        reportConfigToAddModList: 1 item
            Item 0
                ReportConfigToAddMod
                    reportConfigId: 1
                    reportConfig: reportConfigEUTRA (0)
                        reportConfigEUTRA
                            triggerType: event (0)
                                event
                                    eventId: eventA3 (2)
                                        eventA3
                                            a3-Offset: 0dB (0)
                                            .... .0.. reportOnLeave: False
                                    hysteresis: 1dB (2)
                                    timeToTrigger: ms640 (11)
                            triggerQuantity: rsrp (0)
                            reportQuantity: both (1)
                            maxReportCells: 1
                            reportInterval: ms1024 (4)
                            reportAmount: r8 (0)
        measIdToAddModList: 2 items
            Item 0
                MeasIdToAddMod
                    measId: 1
                        measObjectId: 1
                        reportConfigId: 1
            Item 1
                MeasIdToAddMod
                    measId: 2
                        measObjectId: 2
                        reportConfigId: 1

 

Measurement Report

UL-DCCH-Message ::= {
measurementReport-r8
    measResults
        measId: 2
        measResultPCell
            rsrpResult: -85dBm <= RSRP < -84dBm (56)
            rsrqResult: -11dB <= RSRQ < -10.5dB (18)
        measResultNeighCells: measResultListEUTRA (0)
            measResultListEUTRA: 1 item
                Item 0
                    MeasResultEUTRA
                        physCellId: 2
                        measResult
                            rsrpResult: -83dBm <= RSRP < -82dBm (58)
                            rsrqResult: -5.5dB <= RSRQ < -5dB (29)
}

 

Handover Introduction:

There are 2 types of HO.

1. x2 based HO

2. s1 based HO.

Both of the HO are having 3 steps:

1. HO Preparation
2. HO Execution
3. HO Completion

TEID – Tunnel Endpoint in ID

1. Used in GTP protocol.

2. GTP protocol is present in SGW and PGW.

During session request message from SGW to PGW, TEID of Tx will be sent to PGW and in session response message, TEID of Rx will be sent to Tx.

After that, data can be sent between both SGW and PGW.

 

 

 

 

 

 

 

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