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IRAT Measurements-GSM,WCDMA,LTE,TD-SCDMA IRATs

This page describes basics of Inter RAT(IRAT) measurements.It is useful for multimode modem design covering GSM,WCDMA,LTE and TD-SCDMA IRATs.

This page describes typical measurements carried out for Inter-RAT (IRAT) when the UE is active in one RAT. UE or mobile does measurements in IDLE as well as connected mode. This is done to assure that UE always keep connected with the best sell around. Hence UE monitor cells on other frequencies than the serving or camped on cell, i.e. inter-frequency as well as inter-RAT neighboring cells.

This is possible with multi-mode or multi-RAT featured UE/Mobile subscriber. Multi-RAT mobile supports all the possible available RATs as per manufacturer. It can be GSM, WCDMA, LTE or TD-SCDMA etc. In most of the RATs specific location is not provided in the frame for measurements. In these scenarios measurement gaps need to be published for the purpose.

GSM

Measurement parameters: RSSI, BSIC Identification and BSIC re-confirmation
•  During idle mode and in connected mode and carried out during idle frame time slot in 51 frame multi-frame.

WCDMA

Measurement parameters: Scrambling code, RSCP, DL channel, RSSI, Ec/No, Path loss
•  As WCDMA has continuous frame structure and there is no dedicated slots for measurements the compressed mode is used to inserts gaps into the mobile phone's transmit and receive signals. This can be done in various ways.

LTE

Measurement parameters: EARFCN, Cell ID, RSRP, RSRP decode, RSRQ, RSRQ decode
•  In LTE different algorithms are designed to decide how long to spend on BSIC identification of the cells and when to do that. In the case of LTE Connected mode the requirements for BSIC Identification are specific to the DRX configuration and periodicity of the UE.

Following table mentions specifications defined in 3GPP for publishing the gaps and measurement durations for different RATs based on controlling and non-controlling modes. These specifications are very useful for IRAT measurements.

Requirement Standard Reference
GSM Idle Mode RSSI measurement requirement 3GPP TS 45.008, Section 6.6.1
GSM Idle Mode BSIC Reconfirmation Measurement Requirement 3GPP TS 45.008, Section 6.6.1
GSM Non Controlling Mode, active RAT in Idle Mode RSSI Measurement Requirement 3GPP TS 25.133,Section 4.2.2.5/3GPP TS 36.133 section 4.2.2.5.3
GSM Non Controlling Mode, active RAT in Idle Mode BSIC Identification Measurement Requirement When GSM stack is in Non-Controlling mode, the maximum time to identify a new GSM cell is defined to be 3*TmeasureGSM. This implies that finding FCCH-SCH on a new neighbor cell should not exceed 3 times TmeasureGSM
GSM Non Controlling Mode, active RAT in Idle Mode BSIC reconfirmation Measurement Requirement 3GPP TS 25.133, Section 4.2.2.5/3GPP TS 36.133 section 4.2.2.5.3
GSM Connected Mode, BSIC reconfirmation Measurement Requirement 3GPP TS 45.008 Section 7.2, 10.1.1.2
GSM Connected Mode, BSIC identification Measurement Requirement 3GPP TS 45.008 Section 7.2, 10.1.1.2
GSM Connected Mode, Sync Measurement Requirement 3GPP TS 45.008 Section 7.2, 10.1.1.2
GSM Connected Mode, RSSI Measurement Requirement 3GPP TS 45.008 Section 7.2, 10.1.1.2
GSM in non Controlling Mode, LTE in connected, RSSI Measurement Requirement 3GPP TS 36.133, Section 8.1.2.4.5.1.1
GSM in non Controlling Mode, LTE in connected Non-DRX, Sync Measurement Requirement 3GPP TS 36.133, section 8.1.2.4.5.1.2
GSM in non Controlling Mode, LTE in connected DRX, Sync Measurement Requirement 3GPP TS 36.133, section 8.1.2.4.5.1.2
Neighbour Cell RSSI Measurements In WCDMA FACH State 3GPP TS 25.133, section 8.4.2.5.1
BSIC validation & reconfirmation for 9eighbor cells In In WCDMA FACH State 3GPP TS 25.133, Section 8.4.2.5.2.1
BSIC validation & reconfirmation for 10 neighbor cells In In WCDMA DCH State 3GPP TS 25.133, Section 8.4.2.5.2.2
Scheduling of Gaps 3GPP TS 25.133, Section 8.4.2.5
Neighbour Cell RSSI Measurements In WCDMA DCH State 3GPP TS 25.133, section 8.1.2.5.1
BSIC validation & reconfirmation for neighbour cells In In WCDMA DCH State 3GPP TS 25.133, Section 8.1.2.5.2
BSIC validation & reconfirmation for neighbour cells In In WCDMA DCH State 3GPP TS 25.133, Section 8.1.2.5.2

IRAT RELATED LINKS

IRAT handover, Read More➤➤
Also refer tutorials on various RAT types such as LTE, GSM, UMTS, CDMA etc.
LTE Tutorial   CDMA Tutorial   GSM Tutorial   UMTS Tutorial  

RF and Wireless Terminologies


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