# Threshold-based Selective Cooperative-NOMA

## TL;DR

This paper introduces a threshold-based selective cooperative-NOMA scheme that enhances data reliability by reducing error propagation, with analytical derivations and simulations confirming its superior performance over conventional methods.

## Contribution

The paper proposes a novel threshold-based selective cooperative-NOMA method that improves reliability and derives exact BEP expressions for various modulations.

## Key findings

- TBS-C-NOMA outperforms C-NOMA in reliability.
- Optimal threshold minimizes bit error probability.
- Full diversity order achieved by the proposed scheme.

## Abstract

In this letter, we propose threshold-based selective cooperative-NOMA (TBS-C-NOMA) to increase the data reliability of conventional cooperative-NOMA (C-NOMA) networks. In TBS-C-NOMA, the intra-cell user forwards the symbols of cell-edge user after successive interference canceler (SIC) only if the signal-to-interference plus noise ratio (SINR) is greater than the pre-determined threshold value. Hence, the data reliability of the cell-edge user is increased by eliminating the effect of the error propagation. We derive closed-form end-to-end exact bit error probability (BEP) of proposed system for various modulation constellations. Then, the optimum threshold value is analyzed in order to minimize BEP. The obtained expressions are validated via simulations and it is revealed that TBS-C-NOMA outperforms C-NOMA and full diversity order is achieved.