Performance analysis of a pre-backoff based random access scheme for machine-type communications

To avoid radio access network (RAN) takes place severe congestion when a large number of machine-type communication (MTC) devices send their random access requests to the evolved Node B (eNB) simultaneously, some schemes were proposed by 3rd Generation Partnership Project (3GPP). Group paging is one of the candidate solutions for solving the RAN overload control problem. However, the access success probability is terrible when the group size beyond a certain threshold, thus need to seek for a new feasible solution to surmount the weakness of the group paging scheme. A pre-backoff based random access (PBRA) scheme for MTC was proposed to solve the overload problem effectively when large MTC devices use the traditional random access (TRA) scheme. In the PBRA scheme, some random access requests are uniformly distributed over a pre-backoff window. PBRA scheme can abate the number of MTC devices sending random access requests for a short time and thus can deal with the RAN congestion problem. A simulation manifests that the PBRA scheme is superior to the TRA scheme for group paging scenario in access success probability, average number of preamble transmissions and average access delay of the group paging with various combinations of group size and pre-backoff value.