Troposcatter test results for a high-speed decision-feedback equalizer modem

A digital data modem which can operate at 1.5, 3.1, 6.3, 9.4 or 12.6 Mbit/sec has been developed under the Megabit Digital Troposcatter Subsystem (MDTS) program for operation over Defense Communications System troposcatter links. An adaptive decision-feedback equalizer (DFE) is used in the demodulator to eliminate intersymbol interference, combine diversity channels, and augment the existing diversity configuration with implicit diversity. This paper presents the results of a field test of the MDTS modem, which encompassed generally weak signal and strong multipath conditions. The field test established the capability of the MDTS modem to efficiently communicate digital data over DCS troposcatter links at data rates up to 12.6 Mbit/sec.