Section: A.15 Monitoring of common LAs of overlapping target RAT’s coverage
Content: For CS fallback in EPS, as defined in section 5.1A of 3GPP TS 23.272[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [17], the fallback procedure is likely to be faster if the network can allocate a Location Area to the UE that is the LA of the overlapping target RAT's coverage. For this situation, the MME should avoid allocating TAI lists that span multiple Location Areas of the target RAT, this can be achieved by: - configuring the E-UTRAN cell's TAI to align the LA boundary of the target RAT; - the MME being configured to know which TAIs are within which LA; and - the MME using the TAI of the current E-UTRAN cell to derive the LAI. Also as specified in section 4.3.4 of 3GPP TS 23.272[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [17], to facilitate the alignment of TA boundaries with LA boundaries, the E-UTRAN can gather statistics (from the inbound inter-RAT mobility events of all UEs) of the most common LAs indicated in the RRC signalling. From such measurements per E-UTRAN cell basis, operators 1) can know the common LA(s) of the overlapping target RAT’s coverage for each TA, which is useful to configure the TAI list within which LA boundary to MME, operators can also 2) detect the case that TA spans multiple LAs if different most common LA(s) is/are reported from the E-UTRAN cells in the same TA, operators may take actions to rectify it if needed.