Wideband waveform optimization with energy detector receiver in cognitive radio

This paper investigates the transmitted waveform optimization issues for wideband cognitive radio with energy detector receiver. The motivation is to provide a cheap cognitive radio network with simple and cheap cognitive radio receivers. In cognitive radio, a spectral mask for the transmitted waveform is determined upon spectrum sensing, and arbitrary transmitted spectral shaping is required. Meanwhile, the interferences from primary radio should be notched at the secondary receivers. The contribution of this paper is to optimize the cognitive radio communication link by jointly considering the optimization objective, the spectral constraint at the transmitter and the interference cancellation at the receiver. The optimization objective considered here is to maximize captured signal energy within integration window. The optimization problem is formulated as the Quadratically Constrained Quadratic Program (QCQP), which is known as an NP-hard problem. However, after relaxation, QCQP can be solved by using Semidefinite Program (SDP) plus a randomized algorithm. In addition to SDP, a computationally-efficient iterative method is proposed to give the optimal solution for a special situation where the integrator only captures one sample as the decision statistic.