Random access retransmission scheme for power limited nodes

Conventional retransmission schemes for Random Access Channel (RACH) use a uniform random backoff for time of transmission (ToT). It is shown that if the mobile user equipment (UE) velocity and the carrier frequency are known, time-domain correlation statistics of the fading channel can be inferred and then utilized to adapt ToT. A joint metric that trades off between user fairness and opportunistic channel utilization is proposed, and an optimal backoff probability distribution function is derived for ToT. Through simulations, it is shown that by trading off with transmission delay, reduction in power and average number of retransmissions can be obtained.