Measurement Event

EVENT A1, EVENT A2, EVENT A3, EVENT A4, EVENT A5, EVENT B1, EVENT B2

There are several measurement event in LTE. Which are as below.

Event A1

Event A2

Event A3 

The most important parameters involved in event a3 reporting are listed below:

–     eventA3offset 
–     hysteresis 
–     timeToTrigger 
–     sMeasure
–     cellIndividualOffset–     triggerQuantity 
–     reportAmount
–     reportInterval
–     filterCoefficientRsrp

sMeasure

The RRCConnectionReconfiguration message can also contain a list of cells for which handover is not allowed. These cells are identified by their Physical Cell Identity or by a range of Physical Cell Identities.

Measurements commences on the serving and neighboring cells when the RSRP of the serving cell falls below the value defined in the sMeasure parameter. The user equipment detects neighboring cells via intra frequency searches.

Event A3 is defined as a triggering event when a neighbour cell becomes an offset better than the serving cell.

The UE creates a measurement report, populates the triggering details and sends the message to the serving cell. The parameters that define the trigger include:

• Hysteresisa3: The role of the hysteresis in Event A3 is to make the measured neighbor look worse than measured to ensure it is really stronger before the UE decides to send a measurement report to initiate a handover.
• timetoTriggera3: The role of ttt in Event A3 is to avoid a ping-pong effect.
• CellIndividualoffsetEutran: This parameter is applied individually to each neighbor cell with load management purposes. The higher the value allocated to a neighbor cell, the “more attractive” it will be. This parameter can only be used if the neighbor list is broadcast in SIB4 or in an RRC connection reconfiguration.

• a3offset: This parameter can be found in 3GPP 36.331. It configures the RRC IE a3-Offset included in the IE reportConfigEUTRA in the MeasurementConfiguration IE. The value sent over the RRC interface is twice the value configured, that is, the UE has to divide the received value by 2.The role of the offset in Event A3 is to make the serving cell look better than its current measurement in

And this condition is valid for timetotriggera3.

• At the expiration of timetotriggera3, if the UE does not receive an RRC connection reconfiguration message (handover command) from the eNodeB, then it will start a timer called reportingintervala3. At the expiration of this timer, if the conditions for event A3 are still met and the eNodeB has not responded, then another measurement report will be sent to the eNodeB. This process will continue until the eNodeB responds or until a number of measurement reports given by the parameter reportingamount have been sent.
• The formula used by the user equipment for evaluating entry to EventA3 is shown belowL Based on the picture above, event A3 will trigger when

Based on the picture above, event A3 will trigger when:

RSRP(target) > RSRS(Serving) +a3offset + hysteresisa3 – cellindividualoffsetEutran

And this condition is valid for timetotriggera3.

or

Mn − HysteresisA3 > Ms + a3offset 

Mn = measured value of the neighboring cell (either RSRP or RSRQ)
Ms = measured value of the serving cell (either RSRP or RSRQ)

• The user equipment uses the same offset and hysteresis values to determine when to leave EventA3 when the serving cell improves in RSRP or RSRQ relative to the neighboring cells. The formula used by the UE is shown below:

  Mn + HysteresisA3 < Ms + a3offset

•  reportQuantityA3 parameter indicates whether RSRP or RSRQ measurements, or both, are to be included in the measurement reports
• reportIntervalA3 determines the time interval between measurement reports.
• reportAmountA3 indicates how many reports to send; a value of 0 indicates that the reports should be sent indefinitely whilst the EventA3 condition is active.