Scale-time-code-division multiple access (STCDMA)

In this work, a wavelet-based multiple access system, STCDMA (scale-time-code-division multiple access), which is based on the scale, time, and code orthogonality has been described and its performance has been analyzed for synchronous transmission in an AWGN channel. In a synchronous AWGN channel, Hadamard codebased PN sequences keep their orthogonality and hence STCDMA achieves optimum single-user BPSK performance by using a conventional single-user detector for each user. It also supports a larger number of users than conventional DS-CDMA (six or seven times more than DS-CDMA) if the first (coarsest) scale is thought to be traditional DS-CDMA. When we use other wavelets than the Haar wavelet, or the signature waveforms exhibit some correlation in other environments such as asynchronous AWGN channel and the multipath propagation medium, the system will have multiple access interference.