Optimal radio capacity for hybrid DS/SFH CDMA system in cellular radio

A hybrid direct-sequence/slow frequency hopping code-division multiple-access (DS/SFH-CDMA) system operating in Rayleigh fading is described and its spectral efficiency is estimated in terms of the theoretically achievable average channel capacity (in the sense of information theory) per user. The analysis covers the operation over a broadcast cellular time-varying link and leads to a simple, novel closed-form expression for the optimal number of simultaneously active users per cell based on the maximisation of the achieved spectral efficiency.