Installation and maintenance of a simulcast system could not be easier. You can effortlessly expand the coverage area by just adding repeaters. Additional pairs of frequencies are not required. Those repeaters can be integrated into the network with simple setup (No reprogramming of radio terminals is necessary).

6.25 kHz FDMA Technology is ideal for Simulcast

In a simulcast system there is an overlapping area where multiple signals arrive from two or more repeater sites. Delay spread means the time difference between receiving the signals according to the distance from the respective repeater sites. Delay spread can make received audio unintelligible similar to multipath fading which reduces repeater coverage.

The IDAS Simulcast system sends digital voice and data in 4800 bps using 4-Level FSK and 6.25 kHz very narrow bandwidth FDMA technology. Symbol duration is about 420 microseconds (μs). This long symbol duration affects very small Inter-Symbol Interference (ISI). As a result the delay spread tolerance of the IDAS Simulcast system is about 60 μs. The simplicity of a non-linear transmitter and GPS synchronization enables an FDMA digital system to achieve wide repeater coverage as an analog FM simulcast system.

By comparison the delay spread tolerance of a DMR/P25 Phase 1 system is about 30 μs a similar amount reduces the coverage radius. In a P25 simulcast system a more complex Linear Simulcast Modulation system is required to maintain a better tolerance to delay spread and for greater repeater coverage.

Application Example — Highway Railroad Communication Solution

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