Channel Capacity Limits of Cognitive Radio in Asymmetric Fading Environments

TL;DR

This paper analyzes the capacity limits of cognitive radio systems in asymmetric fading environments, considering various fading models and power constraints, and explores the impact of multiple primary users on capacity.

Contribution

It extends previous capacity analyses by deriving distributions for ratios of Rayleigh and Rician variables in asymmetric fading channels, including multiple primary users.

Findings

Capacity behavior differs significantly from symmetric fading scenarios.

Derived distributions enable accurate capacity computation under various constraints.

Multiple primary users influence capacity in complex ways.

Abstract

Cognitive radio technology is an innovative radio design concept which aims to increase spectrum utilization by exploiting unused spectrum in dynamically changing environments. By extending previous results, we investigate the capacity gains achievable with this dynamic spectrum approach in asymmetric fading channels. More specifically, we allow the secondary-to-primary and secondary-to-secondary user channels to undergo Rayleigh or Rician fading, with arbitrary link power. In order to compute the capacity, we derive the distributions of ratios of Rayleigh and Rician variables. Compared to the symmetric fading scenario, our results indicate several interesting features of the capacity behaviour under both average and peak received power constraints. Finally, the impact of multiple primary users on the capacity under asymmetric fading has also been studied.