Energy-Constrained Uncoordinated Multiple Access for Next-Generation Networks

This article analyzes the performance of a distributed joint power/packet diversity random access scheme in the presence of energy requirements. In particular, the two main approaches separately developed in the recent years for exploiting the Interference Cancellation (IC) capabilities of modern receivers, that is, Non-Orthogonal Multiple Access (NOMA) and Packet Repetition (PR), are firstly compared and then combined by imposing a constraint on the total available power. This constraint, which is alternative to the commonly adopted one based on the maximum power allowed for a transmission, results much more practical, since it enables to better infer the energy efficiency of a scheme, be it a pure NOMA, PR or combined NOMA/PR one. Both theoretical derivations and numerical simulations are carried out to evaluate the success probability and the throughput of the considered schemes by accounting for evolved reception criteria and different fading scenarios. Furthermore, the influence of several nonidealities, including imperfect IC and packet overhead, is discussed together with the impact of the system parameters, such as the user rate, the average signal to noise ratio, and the number of slots that compose a random access frame.