# OFDMA-based DF Secure Cooperative Communication with Untrusted Users

## TL;DR

This paper investigates resource allocation in OFDMA-based secure cooperative communication with untrusted users, employing a trusted relay, and formulates optimization problems to enhance sum rate and fairness.

## Contribution

It introduces novel optimization frameworks for secure OFDMA communication with untrusted users using a trusted relay, solved via KKT conditions.

## Key findings

- Optimal resource allocation strategies derived.
- Enhanced secure sum rate achieved.
- Efficient power minimization under fairness constraints.

## Abstract

In this letter we consider resource allocation for OFDMA-based secure cooperative communication by employing a trusted Decode and Forward (DF) relay among the untrusted users. We formulate two optimization problems, namely, (i) sum rate maximization subject to individual power constraints on source and relay, and (ii) sum power minimization subject to a fairness constraint in terms of per-user minimum support secure rate requirement. The optimization problems are solved utilizing the optimality of KKT conditions for pseudolinear functions.