Throughput enhancement for secondary users in cognitive network

Cognitive radio is an exciting emerging technology that has the potential of dealing with the stringent requirement and scarcity of the radio spectrum. Such revolutionary and transforming technology represents a paradigm shift in the design of wireless systems as it will offer the ability of radio sensing, self adaptation and dynamic spectrum sharing. In this paper, we are interested in the case where secondary users are allowed to communicate concurrently with primary users provided that they do not create harmful interference to the licensed users. More precisely, the secondary transmission will depend on a variable cost that reliably quantifies the interference power generated by the secondary user at the primary base stations. Here, we aim to improve the unlicensed system performance in terms of throughput. For this aim, we propose to use an adaptive modulation as well as an energy optimization at the unlicensed user in order to maximize its data rate. We show that the system throughput depends on several parameters such as the maximum allowed cost and the number of base stations in the primary network, the secondary user location and its transmission energy.