Throughput Analysis For Adaptive Transmission Cognitive Radio

Through this project is presented an adaptive transmission scheme for cognitive radio networks. The proposed scheme perform adaptive modulation using OFDM in order to choose the most bandwidth-efficient signal constellation that can be used for the current channel condition.In the scheme, the secondary base station (BS) sense the spectrum applying cognitive radio capabilities, choosing the optimal band for the transmission and estimating the distance to the primary user. By knowing the distance for the primary user and according to the interference temperature concept the secondary BS could calculate the allowable transmit power for non-harmful interference over the licensed network.As both primary and secondary networks are sharing the same band for transmit data simultaneously, we have found that the throughput of the secondary user is influenced negatively by the interference caused by the primary base station (BS). Latter the secondary network present an elliptical contour map where the primary transmitter is non-centric positioned on it and the axes of the ellipse will change on function of the interference levels caused by the primary BS.Hence, the throughput of the secondary network will depend on the currents channel conditions channel capacity and SINR, due to the parameters interference level, received signal power, transmitted signal power and adaptive modulation.