# Polar-Coded Non-Orthogonal Multiple Access

## TL;DR

This paper introduces a novel polar-coded NOMA framework that enhances spectral efficiency and connectivity in 5G by combining polar coding with NOMA transmission, utilizing a three-stage channel transform and innovative user partition schemes.

## Contribution

It proposes a joint design framework for polar-coded NOMA with new user partition schemes and decoding strategies, improving polarization and system performance over existing turbo coded NOMA.

## Key findings

- Outperforms turbo coded NOMA in error rate performance.
- Uses a three-stage channel transform for effective polarization.
- Employs scheduling strategies that enhance decoding efficiency.

## Abstract

Non-orthogonal multiple access (NOMA) is one of the key techniques to address the high spectral efficiency and massive connectivity requirements for the fifth generation (5G) wireless system. To efficiently realize NOMA, we propose a joint design framework combining the polar coding and the NOMA transmission, which deeply mines the generalized polarization effect among the users. In this polar coded NOMA (PC-NOMA) framework, the original NOMA channel is decomposed into multiple bit polarized channels by using a three-stage channel transform, that is, user$\to$signal$\to$bit partitions. Specifically, for the first-stage channel transform, we design two schemes, namely sequential user partition (SUP) and parallel user partition (PUP). For the SUP, a joint successive cancellation detecting and decoding scheme is developed, and a search algorithm is proposed to schedule the NOMA detecting order which improves the system performance by enhanced polarization among the user synthesized channels. The "worst-goes-first" idea is employed in the scheduling strategy, and its theoretic performance is analyzed by using the polarization principle. For the PUP, a corresponding parallel detecting scheme is exploited to reduce the latency. The block error ratio performances over the additive white Gaussian noise channel and the Rayleigh fading channel indicate that the proposed PC-NOMA obviously outperforms the state-of-the-art turbo coded NOMA scheme due to the advantages of joint design between the polar coding and NOMA.