On the adaptive determination of the number of preambles in RACH for MTC

Recently, in the Long Term Evolution-Advanced (LTE-A) system, a random access method, called random access (RACH) procedure, has been proposed for machine-type communications (MTC) to support a number of devices. Since the RACH procedure is similar to multichannel ALOHA, the fast retrial can be employed. In this letter, when the fast retrial is used for the RACH procedure, we propose an adaptive approach that can adaptively decide the number of preambles to maximize the throughput without knowing the number of devices and the access probability.