When LTE eNB asks for measurements, let's have a look at how it goes through. UE measurement is configured with RRC Connection Reconfiguration procedure. Here is protocol sequence for that. Definitely RRC Connection Reconfiguration with measConfig option gives LTE devices preparation of cell measurement from when it is received. There are several kinds of new IEs under this message below.
First of all, this RRC Connection Reconfiguration for this purpose has measConfig node, which includes measObjectIDs, reportConfigIDs, and measIDs. measObjectIDs define measured object cells with channel numbers and reportConfigIDs does measurement and report criteria for instance events or periodic type. In the end of the message, measIDs combine both measObjectIDs and reportConfigIDs as process IDs.
Here is measConfig IE node of a simple RRC Connection Reconfiguration message. You may notice a few nodes in blue and red, which are mapped to the gray blocks below.
- measObjectID: defines measured object cell (e.g. carrierFreq)
- reportConfigID: defines measurement and report criteria (e.g. Events)
- measID: combines both measObjectID and reportConfigID as process ID
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
quantityConfig
quantityConfigEUTRA
measGapConfig: setup (1)
setup
gapOffset: gp0 (0)
gp0: 30
If measured values meet what measConfig (measObjectID, reportConfigID, and measID), this kind of Measurement Report can be anticipated. It delivers what is defined as reportQuantity under RRC Connection Reconfiguration as well as measured cell's physical cell ID. One of measIDs with PCell (Primary or Serving Cell) measured value must be reported and may include NeighCells one.
Then here is an example Measurement Report devices are sending below.
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)
# References
Then here is an example Measurement Report devices are sending below.
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)
# References
- TS36.331 5.5.1 Introduction
- TS36.331 5.5.2 Measurement configuration
- TS36.331 6.3.5 Measurement information elements
- LTE, The UMTS Long Term Evolution From Theory to Practice 3.2.5 Measurements