Adaptive biorthogonal local discrete cosine transform for interference excision in direct sequence spread spectrum communications

A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine transform (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional transform domain excision algorithms is that the basis functions are not fixed but can be adapted to the time-frequency structure of the interfering signal. It is well suited to transform domain compression and suppression of various types of interference. Compared to the discrete wavelet transform (DWT) that provides logarithmic division of the frequency bands, the adaptive BLDCT can provide more flexible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) performance and the increased robustness of the receiver.