Applications of the wavelet transform in spread spectrum communications systems

In communication applications, particularly ones using spread spectrum (SS) techniques, transform domain processing can be utilized to suppress undesired interference and, consequently, improve system performance. Since traditional applications requiring transform domain processing perform excision only in the Fourier domain, one of the main objectives of this paper is to extend transform domain processing to include wavelets as the basis functions. Specifically, the use of wavelets in the excision of jamming signals from SS communications will be investigated. Simulations have been performed using several basis functions for an SS receiver with narrowband jamming. Results of this simulation are presented, including BER figures, and compared with conventional Fourier domain processing. Implementation of the exciser using multirate digital filtering filters is also discussed. An intercept receiver which employs wavelet transform domain excision is also described. The receiver detects DS-BPSK spread spectrum signals in the presence of narrow-band interference by employing adaptive interference rejection techniques. The improvement in the system performance over that of conventional radiometric detection only is shown by presenting numerical simulation results of probability of detection versus false alarm as the receiver-operating- characteristic (ROC) for an enhanced total power detector.