  A new random access scheme is proposed to solve the intra-cell pilot
collision for M2M communication in crowded asynchronous massive multiple-input
multiple-output (MIMO) systems. The proposed scheme utilizes the proposed
estimation of signal parameters via rotational invariance technique enhanced
(ESPRIT-E) method to estimate the effective timing offsets, and then active UEs
obtain their timing errors from the effective timing offsets for uplink message
transmission. We analyze the mean squared error of the estimated effective
timing offsets of UEs, and the uplink throughput. Simulation results show that,
compared to the exiting random access scheme for the crowded asynchronous
massive MIMO systems, the proposed scheme can improve the uplink throughput and
estimate the effective timing offsets accurately at the same time.
