On the performance of sequences for uplink QS-CDMA system [articol]

Abstract

Loosely Synchronized (LS) sequences having Interference Free Window (IFW) are considered to be good candidates for QS-CDMA systems. The recent LS sequence constructions have generated very small sets of sequences exhibiting IFW, thus making them suitable for lightly loaded QS-CDMA. In this paper, it is shown that under certain scenarios for generalized lightly loaded QS-CDMA, there exist traditional sequences, that give either comparable performance or outperform LS sequences, in terms of cross-correlation values. We have demonstrated our results, using short length sequences of length L=31, 32and 38. We have shown that for a QSCDMA system with 15 users, and with chip delays equal to IFW of LS sequences, subsets of WH and Oppermann sequences outperform family of LS sequences. Also, either they give comparable performance or outperform LS sequences, when compared for 8 user QS-CDMA system, with a single or two user delays, 1-3 chips outside the IFW of LS sequences. Moreover, to demonstrate our results we have compared BER of uplink QS-CDMA system in AWGN channel, using different sequence subsets and different scenarios.