Hybrid NOMA-TDMA for Multiple Access Channels with Non-Ideal Batteries and Circuit Cost

TL;DR

This paper explores a hybrid NOMA-TDMA multiple access strategy for channels powered by non-ideal batteries with internal resistance, showing it outperforms traditional TDMA in maximizing sum-rates and achievable rate regions.

Contribution

It introduces a hybrid NOMA-TDMA approach for non-ideal battery-powered channels, demonstrating its superiority over pure TDMA in certain conditions.

Findings

Hybrid NOMA-TDMA outperforms TDMA in sum-rate maximization.

Internal resistance affects the optimal multiple access strategy.

NOMA and TDMA are contained within the hybrid strategy's rate region.

Abstract

We consider a multiple-access channel where the users are powered from batteries having non-negligible internal resistance. When power is drawn from the battery, a variable fraction of the power, which is a function of the power drawn from the battery, is lost across the internal resistance. Hence, the power delivered to the load is less than the power drawn from the battery. The users consume a constant power for the circuit operation during transmission but do not consume any power when not transmitting. In this setting, we obtain the maximum sum-rates and achievable rate regions under various cases. We show that, unlike in the ideal battery case, the TDMA (time-division multiple access) strategy, wherein the users transmit orthogonally in time, may not always achieve the maximum sum-rate when the internal resistance is non-zero. The users may need to adopt a hybrid NOMA-TDMA strategy which combines the features of NOMA (non-orthogonal multiple access) and TDMA, wherein a set of users are allocated fixed time windows for orthogonal single-user and non-orthogonal joint transmissions, respectively. We also numerically show that the maximum achievable rate regions in NOMA and TDMA strategies are contained within the maximum achievable rate region of the hybrid NOMA-TDMA strategy.