MME polling area

Question

In MME polling no change of MME is required while UE moves around the among various enbs belonging to same MME polling area.

so my question is that is it necessary to do tracking area update of a MME within MME Pooling Coverage Area?

Answer 1

In LTE technology, there is many to many mapping between eNodeBs and MMEs. So a set of MME put into a pool for load balancing and redundancy purpose. If we see S1 SETUP RESPONSE message from 3GPP 36.413 then in this message MME tells to eNodeb about Its group id (basically pool) and its code within pool and of course severing PLMN. MME also tells about its relative capacity wrt other MMEs in pool. so whenever an UE attaches if UE doesn't inform about its GUMMEI in RRC Connection Setup complete message. eNodeb executes load balancing among MMEs of pool. Sometimes something happen in the network and an MME reaches its threshold in that case MME send an Overload start message to stop accepting any new connection. For the existing UEs MME can initiate context release command towards eNB with cause (Control Processing Overload) and in turn eNB trigger RRC Connection Release for Ue with cause loadBalancingTAUrequired. In this way UE changes MME.