Measurement Reports in 4G LTE – Part 1

Measurement Reports in 4G LTE – Part 1

Measurement Reports in 4G LTE are a way for a UE (“User Equipment”) or the mobile terminal to keep track of different signal strength measurements and report to the eNodeB if certain conditions are met.

These conditions as reported as Measurement Reports assist the eNodeB in making handover decisions.

LTE Model

A Measurement Reports in 4G LTE are found as part of a UL_DCCH message sent from the UE to the eNodeB that is connected to, in a QXDM Log file, or DIAG protocol should return a value:

UL_DCCH / MeasurementReport Radio Bearer ID: 1, Freq: 5230, SFN: 0

The payload of a a measurement report will contain:

Interpreted PDU:

value UL-DCCH-Message ::=  
{
message c1 : measurementReport :
{
criticalExtensions c1 : measurementReport-r8 :
{
measResults
{
measId 7,
measResultPCell
{
rsrpResult 48,
rsrqResult 12

},
measResultNeighCells measResultListEUTRA :
{
{
physCellId 127,
measResult
{
rsrpResult 48,
rsrqResult 11
}
}
},
measResultServFreqList-r10
{
{
servFreqId-r10 1,
measResultSCell-r10
{
rsrpResultSCell-r10 49,
rsrqResultSCell-r10 12
}
},
{
servFreqId-r10 2,
measResultSCell-r10
{
rsrpResultSCell-r10 43,
rsrqResultSCell-r10 11
}
}
}
}
}
}
}

The first para of he measurement report will contain an Id that matches, a measConfig message that will be discussed later. 

The measResults, contains the PCell or the “Primary Cell,” and depicted st “measResultPCell”  as well as the following parameters contain the RSRP and RSRQ result of that measurement.

measResults 
{
measId 7,
measResultPCell
{
rsrpResult 48,
rsrqResult 12

},

The measurement Reports in 4G LTE contains the values of the SCell or the “Secondary Cell” as well as the “Neighbor Cells” as part of “measResultNeighCells” structure, again with RSRP and RSRQ Values.

    measResultNeighCells measResultListEUTRA :  
                   { 
                     { 
                       physCellId 127, 
                       measResult  
                       { 
                         rsrpResult 48, 
                         rsrqResult 11 
                       } 
                     } 
                   }, 

The SCell-r10, includes values for a servFreqId-r10 with value 1 and servFrequId-r10 with value 2, and he measurement Result, or measResultSCell-r10 for both frequencies, which are provided by the UE as rsrpResultSCell-10 and rsrqResultScell-r10.


measResultServFreqList-r10
{
{
servFreqId-r10 1,
measResultSCell-r10
{
rsrpResultSCell-r10 49,
rsrqResultSCell-r10 12
}
},
{
servFreqId-r10 2,
measResultSCell-r10
{
rsrpResultSCell-r10 43,
rsrqResultSCell-r10 11
}
}
}

What is PCell and Scell values reported by the UE?

PCell is a Primary Cell and SCell are secondary cells, which are used for “Carrier Aggregation” function. 

These are frequencies used for Carrier Aggregation (“CA”) function.  The 3GPP.org organization shows the following image:

Carrier Aggregation

We won’t discuss how “CA” works but the site https://www.3gpp.org/technologies/keywords-acronyms/101-carrier-aggregation-explained illustrates how in green and red two Secondary Cells, and the Primary cell is located in blue. 

Figure 3


Events and Measurement Report

AS shown in the measResults, a value called  measId, for example 7, is  reported by the UE. 

I will go over the RRC Connection Reconfiguration Message and the System Information Block 4 (SIB4) that provides a list of Cells to the UE with different events and different thresholds for the UE to check and report with that identifier.  For example a measId of 7 could be part of the A5 event or measId 5 to a B2 event.