Bit about MM/GMM mobility [Under UMTS]
Previous articles were mainly related to radio access of UMTS. UMTS keeps basic NAS protocols same (with few additions); in fact this is apparent in network architecture wherein MSC/SGSN is continued from GSM/GPRS.
As seen in earlier articles, UMTS introduce cell level mobility handling in RRC connected mode. So what happen to mobility that is being handled by MM/GMM. Mobility is continued to be handled in terms of LA/RA during RRC idle mode. It is interesting to see RRC state and MM/GMM state transitions. An example of these transitions is given below (you want also want to refer GMM state transitions diagram).
As mentioned earlier, NAS procedures remain mostly same as their GSM/GPRS counterparts. In next article, we will take a look at inter-SGSN RA update as an example (we will not much look at network side exchanges; we will only mention the steps).
References: UMTS by Sanchez and Thioune, and WCDMA for UMTS by Holma and Toskala.
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