Artificial Bee Colony assisted Spectrum Sharing Scheme for NOMA based Cognitive Radio Networks

In this paper, a cooperative spectrum sharing scheme is proposed for NOMA based cognitive radio networks comprising of primary and secondary networks. The primary network consists of a primary transmitter PT communicating with a primary receiver PU, whereas the secondary network consists of a NOMA based secondary transmitter ST communicating with L secondary users SUs. The primary terminals are separated far apart therefore ST provides assistance as a relay in order to enable their end-to-end communication. Each terminal is equipped with a single antenna therefore end-to-end communication is accomplished in two time-slots. In first timeslot, PT transmits its signal to ST and at the same time one best SU retransmits the primary signal of the last frame to PU. In second time-slot, ST transmits the superimposed signals of primary and secondary networks. In this scenario, sum rate of SUs is maximized while ensuring to guarantee the QoS of PU. Artificial Bee Colony (ABC) global optimization algorithm is employed to solve this transmit power allocation problem which quickly converged to the best solution.