This study is undertaken to determine whether it is possible to develop a realistic computerized mathematical model for FM tactical radios operating under the influence of enemy jamming. A simplified model of the single channel communication system with interference is developed. The various parameters of this model which affect the quality of communications are then discussed. Specifically, performance data for the VRC-12 radio for various signal-to-interference ratios is introduced and a message quality indicator is developed for various received friendly and jamming signal strengths. Next, mathematical relationships for signal propagation over various terrain are introduced. The specific communication links considered were those for air-to-ground, line-of-sight (LOS), and single and multiple obstacle paths. Consideration was also given to the moisture content of the soil as this is an important consideration at the frequencies involved in the analysis. A comparison is then made between the path losses predicted by the various mathematical relationships and actual field tests. It is shown that the developed expressions produce realistic results. These tested signal propagation relationships are then integrated with the VRC-12 radio's performance under interference to produce the final computerized model. In addition to the terrain between friendly transmitter and receiver and enemy jammer and receiver, several other variables are incorporated in the model. The additional variables of the model include frequency, transmitter and jammer output power, antenna height and directivity and jammer location with relationship to the receiver antenna. The completed model explains various interrelationships in this type of communication problem while answering the "what would happen if...?" question. This is done without actually constructing an operating system. The actual output of the computerized model tells the user whether he has excellent, good, fair, poor or unsuitable communications for various battlefield deployments. By changing various characteristics of the problem, i.e., antenna gain, power output, obstacle between jammer and receiver, etc., a means of changing unsuitable communications to acceptable communications is developed. In summary, the results of the analysis show that it is possible to develop a realistic computerized model for tactical communications in a jamming environment. Comparisons of the propagation portion of the model with actual field tests show the results to be an accurate indication of "real world" conditions while the integration of actual equipment performance under co-channel interference adds a realism to the model which enhances its usefulness as a training or planning device.

ADB 006029 Approved for public release; Distribution is unlimited. The opinions and conclusions expressed herein are those of the student-authors and do not necessarily represent the views of the U.S. Army Command and General Staff College or any other governmental agency. (References to these studies should include the foregoing statement.)