Cognitive Multiple Access Network with Outage Margin in the Primary System

TL;DR

This paper analyzes a cognitive radio network where secondary users opportunistically cancel interference to improve spectral efficiency without disrupting primary users, providing exact outage probabilities and optimized power strategies.

Contribution

It introduces a novel scheme using opportunistic interference cancelation in cognitive radios, with exact outage analysis and power optimization methods under various channel information scenarios.

Findings

Achieves higher secondary network rates with interference cancelation.

Provides exact outage probability expressions for primary users.

Validates analytical results with simulations showing improved spectral efficiency.

Abstract

This paper investigates the problem of spectrally efficient operation of a multiuser uplink cognitive radio system in the presence of a single primary link. The secondary system applies opportunistic interference cancelation (OIC) and decode the primary signal when such an opportunity is created. We derive the achievable rate in the secondary system when OIC is used. This scheme has a practical significance, since it enables rate adaptation without requiring any action from the primary system. The \emph{exact} expressions for outage probability of the primary user are derived, when the primary system is exposed to interference from secondary users. Moreover, approximated formulas and tight lower and upper bounds for the ergodic sum-rate capacity of the secondary network are found. Next, the power allocation is investigated in the secondary system for maximizing the sum-rate under an outage constraint at the primary system. We formulate the power optimization problem in various scenarios depending on the availability of channel state information and the type of power constraints, and propose a set of simple solutions. Finally, the analytical results are confirmed by simulations, indicating both the accuracy of the analysis, and the fact that the spectral-efficient, low-complexity, flexible, and high-performing cognitive radio can be designed based on the proposed schemes.