Frequency-Hopping, Multiple-Access, Phase-Shift-Keying System Performance in a Rayleigh Fading Environment
On-Ching Yue · Bell System Technical Journal · 1980
Recently, various Frequency-Hopping, Multiple-Access (FHMA) schemes have been proposed as alternatives to frequency-division (FDMA) techniques for guarding against interference from other users and multipath fading in transmitting digitized speech in mobile radio. While the advantage of frequency diversity against fading is well known, the system degradation of frame-asynchronous FHMA-PSK due to interference from other users and fading has not been studied, except by modeling the interference as additive white Gaussian noise (AWGN). In this paper, we analyze the performance of two FHMA-PSK systems in a Rayleigh fading environment. We assume that the interferers' addresses are assigned at random and derive expressions for the union upper bound on the bit error rate (Pb) for U users, each assigned N frequencies, i.e., N chips. As an example, we consider transmitting digitized speech (R = 31.25 kb/s) over the mobile radio channel (bandwidth W = 20 MHz), using orthogonal coding of rate r = 5/32 (N = 32). For the differentially coherent FHMA-PSK case, the number of users in a two-way radio system is limited to 26 by the performance of the mobile-to-base link, which corresponds to an equivalent bandwidth of 770 kHz per user.