Sequence assignment of Walsh-Hadamard sequences for quasi-synchronous multi-code CDMA systems

In this study, we propose the sequence assignment of Walsh-Hadamard sequences suitable for quasi-synchronous multi-code transmission. One of the important properties of proposed sequences is that any sequences in a sequence set have zero even cross-correlation with any sequences in another set for any time difference. By using the proposed sequences, the BER performance is significantly improved compared with that by conventional sequences with less number of interferences. Moreover, even if all (N) sequences are used simultaneously by different users, a practical BER performance is obtained. Although the proposed sequences have good cross correlation properties, the auto-correlation properties may be worse than general spreading sequences. Therefore, some devices to overcome the effect of multipath fading should be necessary for practical use in mobile radio environment.