what is Relative MME Capacity ?

Question

Relative MME Capacity this IE indicates some number in range 0 to 255. I am not getting what exactly it indicating is it No of UE's going to support ?

Answer 1

An eNodeB can establish s1 setup with multiple MMEs of same the MMEs pool area. In the pool, all the MMEs may not have same capacity due to hardware or software limitation. So a relative value is assigned to each MME of pool and at the time of S1-setup response, it is communicated to eNodeb .

While making S1-connection for an UE, eNodeB considers these relative capacity and forwards the initial UE message to appropriate MME , in case of unavailability registered MME info or S-TMSI or both from UE.

Comments

thanks Vimal Kumar Mishra,
  the range 0 to 255 ,is it saying Nubmer of UE's, or how eNB is deciding based on this value ?

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It doesn't signify # of UEs. It just tells the relative capacity of MMEs. In other words, you can assume capacity in %. It is just telling how to define relative capacity among MMEs in pool.

Answer 2

When a MME is overloaded, it undergoes an offloading procedure where it informs the enodeBs about its reduced-capacity with the help of "Relative MME Capacity" message.

After receiving this message, any new incoming traffic should be forwarded to a different MME. EnodeBs should not forward the newer traffic to any MME which is in offloading-mode.

Tracking Area Update procedure is employed to release the Iu connection & the incoming messages are now redirected to a new MME.