Distributed beamforming for cognitive radio networks

We study a cognitive radio (CR) network with cognitive users communicating in the presence of a primary user. All users are uniformly distributed within a circle. Each user is equipped with a single ideal isotropic antenna. We propose a scheme in which all users collaboratively transmit the signal by adjusting the carrier phase of each transmitter such that the interference caused by the cognitive users to the primary user is reduced. The effect of noise in phase synchronisation on the resultant beampattern is analysed. The statistical distribution of the mainlobe and sidelobe power levels of the beampattern and the carrier-to-interference ratio (CIR) with phase offset is derived.