Estimation of spectral efficiency for MC/DS-CDMA in cellular systems

Abstract

Spectral efficiency is of primary concern in the design of future wireless communications systems. The spectral efficiency achieved by a multicarrier direct-sequence code-division multiple access (MC/DS-CDMA) cellular system operating in a mobile radio environment with Rayleigh fading, is investigated. Spectral efficiency is evaluated in terms of channel capacity (in the Shannon sense) available to each user, estimated in an average sense. It is analytically shown that, under normalized conditions, MC/DS-CDMA spectral efficiency, on downlink, is higher than that of single-carrier DS-CDMA (SC/DS-CDMA). This result is justified by the combination of path-diversity reception, achieved by a conventional coherent RAKE receiver, and frequency diversity provided, in a fading environment, by frequency division multiplexing on a set of orthogonal carriers.