Random Access Parallelization Based on Preamble Diversity for Cellular IoT Networks

In this letter, we propose a novel random access (RA) parallelization technique based on a notion of preamble diversity to effectively mitigate collision problem in cellular internet-of-things (IoT) networks. A key feature of our proposed scheme is to allow simultaneous transmission of multiple preambles at an RA slot, which enables each of IoT devices to attempt multiple RAs in parallel. Accordingly, the occurrence of RA failure can be significantly reduced since our proposed scheme is effective to prevent the case that the entire preambles used by an IoT device are fully collided with the preambles selected by other devices due to the preamble diversity effect. We mathematically analyze our proposed scheme in terms of the RA failure probability. We also formulate an optimization problem to find an optimal number of simultaneously transmitted preambles at the device side to minimize the RA failure probability. Numerical results show that our proposed scheme is effective to support IoT scenario while alleviating the collision problem compared to other competitive schemes.