Spectral-Efficiency of Time-Frequency-Domain Spread Multicarrier DS-CDMA in Frequency-Selective Nakagami-m Fading Channels

In this contribution we study the spectral-efficiency performance of a multicarrier direct-sequence code-division multiple-access system using both time (T)-domain and frequency (F)-domain spreading, which is referred to as TF/MC DS-CDMA for convenience, when communicating over Nakagami-m fading channels. We consider the TF/MC DS-CDMA scheme, since it is a generalized multiple-access scheme that can be readily configured to some other CDMA schemes, so that we can conveniently compare their spectral-efficiency performance. Furthermore, the Nakagami-m fading channel model makes it possible to study the impact of channel quality on the achievable spectral-efficiency. In this contribution, the spectral-efficiency of the TF/MC DS-CDMA is investigated, when various single-user and multiuser detection schemes are invoked, which include optimum detection, minimum mean-square error (MMSE) detection, zero-forcing (ZF) detection and the matched-filter (MF) based detection. One of our conclusions is that channel quality has insignificant impact on the achievable spectral-efficiency of the TF/MC DS-CDMA, when the number of T-domain resolvable paths of the frequency-selective fading channels is sufficiently high.