The new digital cellular SFH900 mobile system, based on "mixed" slow frequency hopping (SFH) combined with time division, is described in detail. The system includes Viterbi quasi-coherent demodulation of GMSK for which performance measurements in multipath conditions are presented. A concatenated coding scheme that takes full benefit of built-in frequency diversity and interference diversity is introduced. A model for SFH cellular performance evaluation is presented and the quality-versus-capacity tradeoff for SFH900 is given for various frequency reuse patterns. With advanced 16 kbit/s speech coding techniques, and including a 25 percent overhead for management and signaling, the spectrum efficiency of a many-celled SFH900 network is around 3.5 users/cell/MHz, a significant increase in comparison to conventional analog systems. SFH provides intrinsic adaptability to varying traffic conditions and enhanced flexibility for multiservice operation. The SFH900 principles, which have been recently validated through field tests, are very promising for second generation cellular systems.

A theoretical analysis of slow frequency hopping is presented together with a comparison to other multiple access techniques. The propagation and modulation models are described and the multiple access protocols are analyzed with an information theory approach. It is explained why the speed of variation of some random variables is important for protocol evaluation. A definition of capacity is given and is first applied to simple systems. Full mathematical evaluations of the protocol referred to as "random SFHMA" are presented for the mobile-to-fixed-station channel, and some simulation results are given for the reverse channel. With realistic propagation parameters (\alpha= 3.5, \sigma = 8dB) and with mobile power control, there can be as many as 87 radiotelephone users per cell in a 25 MHz band. A comparison to the traditional FDMA protocol is presented and it is Shown that slow frequency hopping would be more efficient for future high capacity small cell systems.