Section: 6.16.2.4 Connection Resume in CM-IDLE with Suspend to the same ng-eNB
Content: The target ng-eNB may be the same as the source ng-eNB in the description in the previous subclause. If so the single ng-eNB performs the roles of both the source and target ng-eNB. In particular, a new KNG-RAN* shall be derived even if the UE is resuming to the same cell from where it was suspended. However, there is the following difference. After a successful resume, the ng-eNB shall send N2 Resume Request message to the AMF. Upon reception of the N2 Resume Request message, the AMF shall check its local policy. If the local policy in the AMF indicates that a new NH derivation is needed, the AMF shall increase its locally kept NCC value by one and compute a fresh NH from its stored data using the function defined in Annex A.10. The AMF shall store that fresh pair and send it to the ng-eNB in the N2 Resume Response message. Upon receipt of the N2 Resume Response message from the AMF and if the message includes a {NH, NCC} pair, the ng-eNB shall store the {NH, NCC} pair in the N2 Resume Response message and remove any existing unused stored {NH, NCC} pairs. The {NH, NCC} pair may be used in the next suspend/resume or Xn handover procedures.