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.”
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.
