Optimal Medium Access Protocols for Cognitive Radio Networks

TL;DR

This paper develops optimal and low-complexity medium access control protocols for cognitive radio networks, enabling efficient spectrum utilization by balancing exploration of channel availability and exploitation of known information, for both single and multiple cognitive users.

Contribution

It introduces the first optimal medium access strategy for unknown channel availability and proposes low-complexity protocols for multi-user cognitive radio environments.

Findings

Optimal strategy derived for single-user scenario

Asymptotically optimal low-complexity strategy developed

Protocols effectively balance exploration and exploitation

Abstract

This paper focuses on the design of medium access control protocols for cognitive radio networks. The scenario in which a single cognitive user wishes to opportunistically exploit the availability of empty frequency bands within parts of the radio spectrum having multiple bands is first considered. In this scenario, the availability probability of each channel is unknown a priori to the cognitive user. Hence efficient medium access strategies must strike a balance between exploring (learning) the availability probability of the channels and exploiting the knowledge of the availability probability identified thus far. For this scenario, an optimal medium access strategy is derived and its underlying recursive structure is illustrated via examples. To avoid the prohibitive computational complexity of this optimal strategy, a low complexity asymptotically optimal strategy is developed. Next, the multi-cognitive user scenario is considered and low complexity medium access protocols, which strike an optimal balance between exploration and exploitation in such competitive environments, are developed.