Performance evaluation of commercial satcom modems with respect to interference and nuisance jamming

Commercial-off-the-shelf (COTS) satellite-communications equipment provides many advantages for today's military satellite-communications systems in terms of cost, availability, and flexibility. The relationship and importance of using COTS equipment for military applications and incurring potential vulnerability to enemy jamming and interference is stressed in this paper. In order for a communications system to be of value, it must be reliable and it must be available when needed. The idea of this paper is making the most of the capabilities that do exist commercially in order to improve the probability that communication based on commercial equipment and systems will be available when needed, at least when interference and very modest jamming capability via a transportable terminal are considered. The bit-error probability for commercial satellite-communications modems which employ BPSK or QPSK modulation as well as convolutional coding and concatenated coding is computed analytically taking into account broad-band noise, pulsed noise, and pulsed tone interference. The results show that in broad-band interference at moderate and high values of signal-to-interference-plus-noise ratios, concatenated Reed-Solomon and soft-decision convolutional coding provides the best performance, whereas at low signal-to-interference-plus-noise ratios, the types of coding considered offer worse performance than the uncoded system. When pulsed interference is considered, the optimum coding method depends on the signal-to-interference-plus-noise ratio. Experimental results are also included.