A Novel RACH Scheme for Efficient Access in 5G and Beyond Networks using Hash Function

Abstract

With more subscribers and a variety in business use cases relying on 5G New Radio (NR) network infrastructure, the access network needs to be scalable. The initial network access procedure comprises of users sending preambles to gNB for granting uplink (UL) resources. However, limited preambles in 5G NR can be a bottleneck on the performance of network access procedures. Preamble collisions during initial Random Access Channel (RACH) procedure can limit the scalability of the network. With the increase in the number of cellular User Equipments (UEs) and Machine Type Communication (MTC) devices, the probability of such preamble collisions further increases, thereby leading to reattempts by UEs. This in turn, results in increased latency and reduced channel utilization. In this work, we have used hash functions for selecting preambles during the RACH process. We have used modulo hash functions to convert device identifiers into preamble indexes such that the collision is reduced. In order to counter collisions while using hash functions, we have adopted standard collision resolution techniques such as linear probing, quadratic probing, and double hashing. On performing extensive simulations, it is observed that the hashing based access scheme performs better than the standard Access Class Barring (ACB) scheme in effectively reducing the number of collisions thereby empowering more users to access the network.