Abstract
Cognitive radios are a natural evolution of Software Defined Radios (SDRs) that are supposed to be equipped with the ability to learn their RF environment and reconfigurability. A cognitive radio can communicate over a primary user’s channel as long as the introduced interference does not degrade the primary Signal-to-Interference-plus-Noise-Ratio (SINR) below its minimum Quality of Service (QoS) requirement. In this paper, we employ cooperation in data transmission in order to increase the secondary transmit power limit. We present an optimal power allocation scheme for secondary users in order to achieve maximum SINR. We show that the optimal channel assignment problem that maximizes the sum-rate can be solved via the so-called Hungarian algorithm at a cubic complexity order. Also, we develop a suboptimal algorithm that permits to solve the channel assignment problem with a quadratic complexity order and with a slight performance degradation compared to that of the optimal solution.
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