Call Blocking in Spectrally Constrained FDMA/DAMA SATCOM Systems

A problem in the use of satellite Demand-Assigned Multiple Access (DAMA) results from spectrum limitations at each ground terminal due to avoiding frequency interference to nearby terrestrial microwave radio relay. Frequency Division Multiple Access (FDMA/DAMA) can operate with a terminal-by-terminal assignment of frequency channels out of the total band available to the satellite. Time Division Multiple Access (TDMA) requires the use of the full band at all the terminals. The effect on satellite bandwidth utilization must be evaluated to determine the advantage, if any, of FDMA channel-by-channel assignment. A linearized traffic model is presented for making such an analysis. The FDMA/DAMA traffic load allowed by spectrum constraints falls off as a function of the manner in which frequency channels and traffic are distributed over the terminals. Additionally, a somewhat more complex geometric model is proposed.