Telemetry Channel Capacity Assessment for Reentry Vehicles in Plasma Sheath Environment

Channel capacity is the prerequisite and basis for the design of a communication system. To assess the impact of a harsh plasma environment on the communication system of reentry vehicles, Shannon’s information theory is used to evaluate the channel capacity through the estimation results of the signal-to-noise ratio obtained by the communication link budget method. First, the attenuation caused by the plasma sheath is calculated with a stratified medium finite-difference time-domain method for typical S, C and Ka telemetry frequencies in a typical reentry plasma environment. Thereafter, typical telemetry transceiver parameters are considered to estimate the channel capacity. Results show that the S-band channel capacity is almost zero at the altitude of 30-40 km and the plasma attenuation at the C-band is slightly better. However, the blackout phenomenon remains obvious. The Ka-band signal can penetrate the plasma sheath layer with the smallest attenuation, thus significantly increasing the capacity of the channel and it may thus adequately meet telemetry needs.