Doubly orthogonal wavelet packets for DS-CDMA communication

Wavelet packets have been found a promising candidate for user signature waveforms in code division multiple access communication systems. The waveforms are usually chosen from an orthonormal basis so that there will be no interference between different users. However, timing errors may cause these signature waveforms to lose orthogonality to each other. In this paper, we describe a signal set which utilizes double orthogonality based on wavelet packets and binary Walsh codes. This double orthogonality produces auto- and cross-correlations that are much better than the conventional wavelet packet sets and are comparable to the pseudo random binary codes. The double orthogonality may also enable easy implementation in low complexity receiver design