US Army tactical LOS radio propagation reliability

The authors summarize the results obtained by the US Army Communications-Electronics Command (CECOM) Line of Sight (LOS) Propagation Working Group, which was formed in April 1991 to investigate reports of tactical LOS radio outages in Southwest Asia (SWA) that appeared to be propagation related. Discussions with tactical LOS operators led to the conclusion that multipath fading on UHF and SHF links was a common problem, resulting in a significant number of communications outages. Subsequent investigation revealed that existing link planning procedures for the Mobile Subscriber Equipment (MSE) Wide Area Communications System UHF multichannel LOS links allocated only a small fixed fade margin for multipath fading. This margin proved to be inadequate in the difficult propagation environment of SWA. A review of current research and modeling in the area of UHF multipath fading led to the development of a new and more flexible multipath fading model, capable of providing more realistic margins for link planning. This model is planned for implementation in new tactical LOS network engineering and planning tools for MSE currently under development by CECOM. The methodology and results from the CECOM fading model, the expected impact of its use for LOS link planning, and current implementation plans are discussed