“A regulatory study and recommendation for EIRP Spectral Density requirement/allowance for SOTM terminals at Ka-Band on WGS system”

The Army's WIN-T program is developing a new class of terminals for satellite on-the-move (SOTM) missions. The initial target satellites were commercial Ku-band satellites however, the ultimate goal is the Wideband Global System (WGS). WGS will consist of a geosynchronous constellation of at least six spacecrafts with X and Ka-band capable transponders. WGS is the newest department of defense (DOD) transponded satellite system. Earth Terminals (ET) that will utilize WGS will need to conform to MIL-STD-188-164A [1]. Currently, the DOD is in the process of updating MIL-STD-188-164A to add mobile satellite communications (SATCOM) requirements. One of the parameters that will be addressed is the off-axis equivalent isotropically radiated power (EIRP) Spectral Density (ESD) for ground mobile terminals. The ESD value is an extremely important parameter that will drive the achievable throughput, spectral efficiency, and adjacent satellite interference (ASI) levels of SOTM terminals and networks. The World Radio Regulations has designated the earth-to-space 30-31 GHz Ka-band, which is the band used by WGS, with a usage designation of co-primary fixed satellite (FSS) and mobile satellite service (MSS). This means that the same criteria used to analyze commercial Ku-band FSS is not applicable. This paper looks at the system impacts of operating small mobile terminals at the 30-31 GHz Ka-band. It develops a methodology to analyze the overall performance impacts for SOTM networks, giving particular consideration to performance and the transmission impacts to adjacent satellite networks (ASN). The ASI will be quantified in terms of Equivalent Satellite Link Noise Temperature (ESLNT)[2] and its equivalent delta-T over T (delta-T/T). The analysis will examine ASI using the ESD limits provided by SMDC/ARSTRAT for WGS. Finally, based on this analysis, the paper will propose an off-axis ESD limits for inclusion in the update to MIL-STD-188-164B.