Suitable Spreading Sequences for Asynchronous MC-CDMA Systems

Abstract

In order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned.

A New Code Family for QS-CDMA Visible Light Communication Systems

“…Due to their zero-correlation property, ZCZ codes have been extensively studied for radio frequency systems (more details can be found in [9], [10]). In [8], the authors introduced optical ZCZ codes to eliminate MAI in an optical QS-CDMA VLC system.…”

Adequate spreading codes to reduce MAI in quasi‐synchronous MC‐DS‐CDMA system

“…Zero correlation zone (ZCZ) are sets of sequences with ideal (zero) correlation properties in a specified zone [9]. Several constructions of ZCZ codes have been proposed [10,11] and studied [12]. Indeed, it was shown in [13] that ZCZ codes can reduce the MAI in single carrier DS-CDMA system in the presence of additive white Gaussian noise (AWGN) and Rician fading.…”