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 (M2M) devices has drawn new attention on the radio access network (RAN). Surging random access attempts cause not only severe preamble collisions but also down-link resource shortage, and thus degrade the performance of random access procedure. However, the effect of down-link resource shortage on system performance is not yet comprehensively studied.
In addition, most existing random access contention resolution mechanisms sacrifice RACH (random access channel) throughput for a high success probability, and thus the price is that low-throughput mechanisms need long time to deal with access attempts. In this work, we evaluate the MAC-level performance for the 4-step random access procedure in LTE systems, for both with and without constrained down-link resources. Further, we propose a novel RACH contention resolution scheme, the dynamic backoff (DB) scheme. DB can achieve high RACH throughput yielding a high random access success probability under various RACH overloaded scenarios.