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/s has been developed under the Megabit Digital Troposcatter Subsystem (MDTS) program for operation over Defense Communications System troposcatter links. An adaptive decisionfeedback equalizer (DFE) is used in the demodulator to eliminate intersymbol interference, combine diversity channels, and augument the existing diversity configuration with implicit diversity. This paper presents the results of a field test of the MDTS modem at the Rome Air Development Center troposcatter test facility during the winter of 1976. The field test, which encompassed generally weak signal and strong multipath conditions, yielded excellent performance results at all data rates. The field tests established the capability of the MDTS modem to efficiently communicate digital data over DCS troposcatter links at data rates up to 12.6 Mbit/s.