Estimation and Adaptation for Bursty LTE Random Access

With the potential to generate numerous connection requests, an explosive growth in the volume of data traffic and the number of mobile and machine-to-machine devices has drawn new attention to the radio access network. Surging random-access attempts cause not only severe preamble collisions but downlink resource shortage as well, thus degrading the performance of the random-access procedure. However, the effect of downlink resource shortage on system performance has yet to be comprehensively studied. In addition, most existing random-access contention resolution mechanisms sacrifice random-access channel (RACH) throughput for a high success probability, and thus, the price is that low-throughput mechanisms need a lot of time to deal with access attempts. In this paper, we evaluate the medium-access-control (MAC)-level performance for the four-step random-access procedure in Long-Term Evolution (LTE) systems, both with and without constrained downlink resources. Furthermore, we propose a novel RACH contention resolution scheme, i.e., the dynamic backoff (DB) scheme. DB can achieve high RACH throughput, yielding a high random-access success probability under various RACH overloaded scenarios.