Bit error rate performance of Haar wavelet based scale-code division multiple access (HW/S-CDMA) over the asynchronous AWGN channel

In this paper, we study a recently proposed multirate system, called wavelet based scale-code division multiple access (W/S-CDMA). W/S-CDMA depends on the code, time and scale orthogonality introduced by pseudo-noise (PN) sequences, and wavelets. In this system, the channel is partitioned into different scales, and each scale into time slots. In addition, the PN sequences are used in each scale to identify multiple users. In W/S-CDMA, each user is assigned a specific scale and PN sequence, and transmits its successive information symbols with its PN sequence and the wavelets in that scale. More symbols are transmitted in finer scales. We analyse the bit error rate performance of Haar wavelet based S-CDMA (HW/S-CDMA) over an asynchronous additive white Gaussian noise (AWGN) channel by using a conventional detector for deterministic PN sequences. The performance of the system is compared to that of an equivalent multirate CDMA (MR-CDMA) system for Gold and Kasami PN sequences. Results show that HW/S-CDMA outperforms MR-CDMA. In addition, because of its suitable format HW/S-CDMA is also capable of employing the optimal PN sequence families with limited number of sequences such as Kasami, Bent, etc. repeatedly in different scales. Copyright # 2006 John Wiley & Sons, Ltd.