An Experimental Performance Evaluation of SCPS-TP over Cislunar Communications Links

Space communication protocol standards-transport protocol (SCPS-TP) is a set of TCP extensions aimed at reliable transfer of information between space mission end systems. Some works have been done on throughput performance evaluation of SCPS-TP over LEO- and GEO-satellite channels. In this paper, we present an experimental performance evaluation of SCPS-TP over a simulated cislunar communication link. We intend to see how effective both the window-based and the rate-based transmission control mechanisms of the SCPS-TP cope with a long cislunar link delay, especially when hybridized with a high bit-error-rate (BER), and which option has throughput advantage over the other. The experimental results reveal that the protocols have statistically significant performance difference over an error-prone link with a BER around 10^-5 at which pure rate control shows superior performance over other three protocols. SCPS-Vegas performs poorly over a long-delayed, error-prone cislunar channel. Quantitatively, the throughput advantage of SCPS-pure rate control is around 3000 bytes/sec over all other three protocols over both symmetrical and asymmetrical channels at BER=10^-5. We conclude that pure rate control is very suitable for a long-delayed, error-prone cislunar communication links.