Spectrum Detection and Parameter Estimation with Compressive Sampling for mW Composite Sequence in Cognitive Radio System

In cognitive radio (CR), hybrid overlay/underlay spectrum access mechanism is a smart way for secondary users (SU) to coexist with primary users (PU) in the same frequency band. m-Walsh (mW) composite sequence spread spectrum technique is a strong candidate for hybrid overlay/underlay due to the low power spectral density (PSD) and spectral nulls. Benefit from the special spectral feature of mW composite sequence, it is available to reduce the complexity of receiver through spectrum detection and parameter estimation for mW composite sequence. In CR networks, secondary users access spectrum in a very wide frequency band range, so it requires high-rate sampling to detect the spectrum of mW composite sequence. By exploiting the sparsity property of transmit signals in frequency band, based on compressive sampling, the modulated wideband converter (MWC) is introduced to reconstruct the spectrum of secondary user from sub-Nyquist samples. Simulation results verify that the spectrum of mW composite sequence spread spectrum signal can be reconstructed accurately by using MWC, and then the spectrum detection and parameter estimation are also performed.