Measurement in LTE

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What is Measurement?

Measurement configuration and measurement report are used by UE while measuring and reporting the strength of signals that it receives from cells. Below figure illustrates the same.

Measurement configuration:

(What does measurement Configuration indicates?)

The measurement configuration indicates what measurement information needs to be reported and is provided by eNB to UE. This measurement configuration is provided by eNB to UE through RRC connection Reconfiguration message when it establishes an RRC connection with the UE. Measurements could be interfrequency, intrafrequency or IRAT (intersystem).

UE can get the following information a measurement configuration includes: Measurement Objects, Measurement Identities, Reporting Configurations, Quantity Configurations and Measurement Gap Configurations:

1) Measurement object:

The objects provides information about EUTRA cells to be measured by UE, including the physical cell ID (PCI) of cells to be measured, black list cell ID, offset values for each cell, frequency channel number, etc.

Note: The blacklisted cells are not considered in measurement reporting or event evaluation.

2) Reporting configuration: 

This specifies triggering events that require UE to send a measurement report message. Each configuration consists of the following:

Trigger type	Periodical/event (A1, A2, A3, A4……)/CGI (Cell Global Identity) reporting (for ANR)
Trigger quantity	Rsrp/rsrq
Report quantity	Same as trigger quantity/both
Max. report cells	1…..8
Report interval	ms120, ms240, ms480, ms640, ms1024, ms2048, ms5120, ms10240, min1, min6, min12, min30, min60, spare3, sapre2, spare1
Report amount	r1, r2, r4, r8, r16, r32, r64, infinity

3)Measurement ID: 

This is used as reference number in the measurement report. (Range 1 ˜ 32). This identifies measurement objects.

Measurement ID = Measurement object ID + Report configuration ID

4)Quantity configuration: 

This shows the values to be measured by UE2. This indicates measurements quantities and associated filtering used for all event evolution and related reporting of that measurement type.

5)Measurement Gap: 

This shows the interval at which neighbor cells are to be measured by UE.

In intra frequency neighbor measurement UE can measure the neighbor cell without using measurement gaps. On the other hand, in inter frequency neighbor measurement UE has to synchronize with the neighbor cell’s frequency and then measure its signal strength by using measurement gaps during UL or DL idle period.

Measurement report triggering:

After measuring the signal strength of serving cell and the neighboring cell the UE reports the results to eNB periodically if periodic timer expire which is configure by eNB or when measurement event is triggered as one of the reporting criteria set by the measurement configuration is satisfied. 

Event A1, A2, A3, A4 and A5 are included in reporting criteria for EUTRA while for inter RAT measurement report include B1 and B2 events.  For triggering handovers event A3 is commonly used.

Measurement report triggering happens once periodic timer expired or event base and CGI report in the case of ANR (automatic neighbor relationship).

In Upcoming Part we will learn more about Measurement in NSA & SA Cases.

Stay tune for more Update…………………

Pinal Dobariya…

References:

1)3GPP TS 36.300

2)3GPP TS 36.331

3)Netmanias Technical Document, “Eleven EMM Cases in an EMM Scenario”