Spacecraft for NASA exploration missions travel large distances and sometimes these missions initiate a long-term communication link between the earth and a mission target, for example, a planet. The distance traveled results in substantially attenuated received signals and both substantial and variable round trip delays. For example, the RTT is about 2.7 seconds between the Earth and Moon, and varies from 8 to 40 minutes between the Earth and Mars. Due to large signal attenuation associated with the distance, BERs in space communications are very high. In addition, non-additive white Gaussian noise (non-AWGN) exists due to factors including the Earth's atmosphere and the sun's corona. Furthermore, the motion and velocity of the transmitter can be unpredictable due to unknown gravity fields and planetary atmosphere, which causes channel variation and uncertainty in space communications.
Most of current space communication standards, techniques and protocols have been migrated from those
employed in land-based communication systems, which were not designed specifically for space
communications. For example, to protect against noise, various coding strategies have been adopted.
Selection of the appropriate rate of these codes, however, assumes a good knowledge of a stationary channel
at the transmitter, which must be developed on a timely basis in close coordination with the receiver. Because
of the large round trip delays involved, high fidelity characterization is seldom achievable in the space
environment. In addition, the current TCP-based transmission protocols are known to perform poorly in
environments having large variances in both propagation delay and path loss. Furthermore, for reliable
communications and signal detection, data collected from different dimensions in space, time and frequency
may need to be fused at the receiver. This project proposes to address these problems, which are inherent to
space communications, at a fundamental level to meet the continuing demand for high quality, high data rate
communications in NASA exploration missions.