Distributed Beamforming with Imperfect Phase Synchronization for Cognitive Radio Networks

In this paper, we present the analysis and simulation evaluation of a cognitive radio network employing a distributed beamforming technique with imperfect phase synchronization in the presence of a primary receiver. Our system model consists of a group of cognitive transmitters, each with an ideal isotropic antenna and equal transmit power, communicating with a secondary receiver in the farfield. The objective of the network of cognitive transmitters is to optimize its beampattern in the direction of the secondary receiver while minimizing the beampattern in the direction of the primary receiver to a certain threshold. The phases of the transmitted signals determine the beampattern, and we demonstrate that an optimization problem can be formulated to determine the phases of the transmitters that satisfy the constraints. We then evaluate the beampattern under imperfect phase synchronization and present how the phase error can impact the performance of beamforming and cause protection to the primary receiver to suffer. The results bring some interesting insights to distributed beamforming with imperfect phase synchronization for cognitive radio networks