Performance of quasi-synchronous scale-time-code division multiple access system over the additive white Gaussian noise channel

Scale-time-code division multiple access (ST-CDMA) depends on the code, time and scale orthogonality provided by pseudo-noise (PN) sequences and wavelets. The performance of an ST-CDMA system is investigated over a quasi-synchronous (QS) additive white Gaussian noise (AWGN) channel. First, the system, designed for Daubechies-2 (Db2) wavelets, is analyzed and its bit error rate performance is obtained. The performance of this system is a little worse than that of QS-CDMA (quasi-synchronous code division multiple access) for the same number of users and bandwidth occupancy. The optimum wavelet, which minimizes the multiple access interference of the system, is obtained by using MATLAB´s optimization toolbox and then the performance of the system outperforms that of QS-CDMA.