On the Capacity of Overlay Cognitive Radios with Partial Cognition

Abstract

This paper considers the problem of interference channel (IFC) with overlay cognitive radio setting. Both achievable rate and outer bounds for an overlay cognitive radio channel are developed, where the cognitive transmitter has partial knowledge of the legitimate transmitter's message. Specifically, an IFC setting is considered where one transmitter (the “cognitive” one) knows the message of the other (“legitimate” transmitter) partially. An outer bound on the capacity region of this channel is found for the “weak” interference case (where the “interference” caused by the cognitive transmitter to the legitimate receiver is weaker than the “signal” from the cognitive transmitter to the cognitive receiver). This outer bound is developed for the discrete-memoryless case and evaluated for a Gaussian channel setting. An achievable region is subsequently determined for a partially cognitive radio channel, and the outer bound on the capacity region is compared with the achievable rate in a Gaussian channel. Subsequently, an achievable region that incorporates elements of the Han-Kobayashi coding strategy with dirty paper coding is developed for this channel.