# On Coverage Probability in Uplink NOMA With Instantaneous Signal Power-Based User Ranking

## TL;DR

This paper derives the coverage probability in uplink NOMA networks considering instantaneous signal power-based user ranking, highlighting inaccuracies in the commonly used mean signal power approximation.

## Contribution

It provides a new analytical derivation of coverage probability based on ISP ranking, improving accuracy over MSP-based methods.

## Key findings

- ISP-based ranking yields higher coverage probability estimates.
- MSP-based ranking underestimates true coverage probability.
- The derived formulas improve the accuracy of performance analysis in uplink NOMA.

## Abstract

In uplink non-orthogonal multiple access (NOMA) networks, the order of decoding at the base station (BS) depends on the received instantaneous signal powers (ISPs). Therefore, the signal-to-interference-plus-noise ratio (SINR) coverage probability for an uplink NOMA user should be calculated using the ISP-based ranking of the users. In the existing literature, however, mean signal power (MSP)-based ranking is used to determine the decoding order and calculate the SINR coverage probability. Although this approximation provides tractable results, it is not accurate. In this letter, we derive the coverage probability for ISP-based ranking, and we show that MSP-based ranking underestimates the SINR coverage probability.