An improved wavelet-packet-division multiple access system

An improved wavelet-packet-division multiple access (WPDMA) system is presented. In a WPDMA environment, each message signal is waveform coded onto a wavelet function to enhance the immunity of the system against interference. We propose a wavelet design method based on numerical optimization to mitigate the effects of asynchronism in the system. In brief, the algorithm consists of two parts: (a) identification of the feasible region, and (b) use of a quasi-Newton search algorithm to find the minimizer. By employing this technique, we found the optimal wavelet function which minimizes the interference due to timing errors. The advantages of the proposed WPDMA design algorithm with respect to a previously reported procedure are discussed.