Carrier Frequency Estimation for Balanceable DS-SS/QPSK Signal in Non-cooperative Communication Systems

Direct sequence spread spectrum (DS-SS) are widely for secure communications. They have many interesting properties including low probability of detection or interception. Since the DS-SS signal uses a broad bandwidth, the power spectral density can below the noise level. Therefore, the signal is difficult to detect and estimate. In this paper, a new algorithm based on fourth-order cumulant is proposed to estimate the carrier frequency of balanceable DS-SS/QPSK signal in non-cooperative communication system. The algorithm does not require a prior knowledge about the signal. In particular, it can restrain the Gaussian noise extremely. The validity of the algorithm has been verified by the computer simulation even in low signal-to-noise ratio (SNR) circumstance.