Analysis of multiplex techniques for land mobile radio service

Two types of frequency multiplexing are theoretically analyzed for their applicability as a form of modulation in the land mobile radio service (LMRS). Both SSB/FM and FM/FM are analyzed for their signal-to-noise ratio (SNR) versus modulation index. These results are normalized to the signal-to-noise performances of the existing 5-kHz deviation system for comparison purposes. The latter performance is developed using the actual Electronic Industries Association (EIA) response of a LMRS receiver. The spectrum of the multiplex system for the case of equal subchannel signal-to-noise is developed using a computer. The spectrum is used to determine the spectrmm occupancy of multiplex systems. Based on the tradeoffs of transmit power and spectrum occupancy, a discussion of the interference characteristics of the multiplex systems compared to the existing system is presented. Finally, conclusions are drawn on the spectrum efficiency of a multiplex system compared to the present system.