Spectral Efficiency Optimized Adaptive Transmission for Cognitive Radios in an Interference Channel

TL;DR

This paper introduces an adaptive transmission scheme for cognitive radios in interference channels, optimizing spectral efficiency without user negotiation, and compares it favorably to existing approaches.

Contribution

It proposes a novel link adaptation and power control scheme for cognitive radios that maximizes spectral efficiency while satisfying primary user requirements without user negotiation.

Findings

The scheme achieves higher spectral efficiency than traditional underlay and interweave methods.

It operates efficiently with a fast, suboptimal solution for nonlinear optimization.

No user negotiation is required for the proposed adaptive transmission scheme.

Abstract

In this paper, we consider a primary and a cognitive user transmitting over a wireless fading interference channel. The primary user transmits with a constant power and utilizes an adaptive modulation and coding (AMC) scheme satisfying a bit error rate requirement. We propose a link adaptation scheme to maximize the average spectral efficiency of the cognitive radio, while a minimum required spectral efficiency for the primary user is provisioned. The resulting problem is constrained to also satisfy a bit error rate requirement and a power constraint for the cognitive link. The AMC mode selection and power control at the cognitive transmitter is optimized based on the scaled signal to noise plus interference ratio feedback of both links. The problem is then cast as a nonlinear discrete optimization problem for which a fast and efficient suboptimum solution is presented. We also present a scheme with rate adaption and a constant power. An important characteristic of the proposed schemes is that no negotiation between the users is required. Comparisons with underlay and interweave approaches to cognitive radio with adaptive transmission demonstrate the efficiency of the proposed solutions.