# Achievable Rate Region of Non-Orthogonal Multiple Access Systems with Wireless Powered Decoder

## TL;DR

This paper investigates the achievable rate region of a NOMA system with wireless energy harvesting at the decoder, proposing a generalized scheme that outperforms traditional time switching and power splitting methods.

## Contribution

It introduces a generalized energy harvesting scheme combining time switching and power splitting, and characterizes the achievable rate region under different decoding power models.

## Key findings

- The generalized scheme achieves larger rate regions than traditional methods.
- Closed-form solutions are derived for constant decoding power.
- Rate-dependent decoding power further enlarges the achievable rate region.

## Abstract

Non-orthogonal multiple access (NOMA) is a candidate multiple access scheme in 5G systems for the simultaneous access of tremendous number of wireless nodes. On the other hand, RF-enabled wireless energy harvesting is a promising technology for self-sustainable wireless nodes. In this paper, we consider a NOMA system where the near user harvests energy from the strong radio signal to power-on the information decoder. A generalized energy harvesting scheme is proposed by combining the conventional time switching and power splitting scheme. The achievable rate region of the proposed scheme is characterized under both constant and dynamic decoding power consumption models. If the decoding power is constant, the achievable rate region can be found by solving two convex optimization subproblems, and the regions for two special cases: time switching and power splitting, are characterized in closed-form. If the decoding power is proportional to data rate, the achievable rate region can be found by exhaustive search algorithm. Numerical results show that the achievable rate region of the proposed generalized scheme is larger than those of time switching scheme and power splitting scheme, and rate-dependent decoder design helps to enlarge the achievable rate region.