Spectral efficiency for a hybrid DS/FH code-division multiple-access system in cellular mobile radio

The spectral efficiency of a hybrid cellular direct-sequence/frequency hopp ing code-division multiple-access (DS/FH-CDMA) system operating in a Raylei gh-fading environment is examined. In this work, spectral efficiency is eva luated in terms of the theoretically achievable channel capacity (in the Sh annon sense) per user, on the condition that this is estimated in an averag e sense. The analysis covers the downlink assuming a static model of operat ion and a direct-sequence/slow-frequency hopping (DS/SFH) as well as a dire ct-sequence/fast-frequency hopping (DS/FFH) scheme. As it is shown, the spe ctral efficiency of cellular DS/FFH-CDMA operating in a Rayleigh-fading env ironment is greater than that of broad-band DS- and DS/SFH-CDNIA systems op erating under normalized conditions. This is justified by the combination o f path-diversity reception as achieved by conventional coherent RAKE receiv ers and the frequency diversity that is inherently present in FFH transmiss ion.