Description

In this proposed system, we investigate joint power and channel allocation problem for the orthogonal frequency division multiplexing (OFDM) based multi-user cognitive radio systems with quality-of-service (QoS) in terms of signal-to-interference-plus-noise ratio (SINR) and proportional rate constraints. The QoS requirement of each cognitive radio user imposed by its minimum SINR and interference introduced by unlicensed secondary users to primary users make power and channel allocation problem more complex. Opportunistic spectrum access using cognitive radio technology is an emerging concept for an efficient utilization of RF spectrum by allowing unlicensed secondary users to access the licensed spectrum without causing harmful interference to the licensed primary users. We present a formal analysis for a proposed approach and illustrate the approach with numerical results obtained from simulations. In this work, we consider joint channel and power allocation for dynamic spectrum access in OFDM based cognitive radio network where secondary users are required to satisfy imposed constraints in terms of minimum SINR, transmit power, proportional rate and interference limit constraints. The problem considered in this paper is very similar to the problem, except two constraints; interference constraints and minimum SINR constraints. Note that the channel allocation is done based on maximum SINR to get high achievable rates which creates harmful interference to primary users in OFDM based cognitive radio systems. Thus, we jointly consider SINR of the channel and interference generated by the secondary users as constraint in optimization problem and presented a solution.