Nasa UM JSU

Motivation

Space communications, providing connection among rovers, spacecraft, space stations, satellites and groundbased control centers, are critical to the success of NASA exploration missions. The purpose of this project is to address several specific space communication challenges, which include substantial and variable round trip time (RTT), uncertainty in the ability to characterize the channel, and the resulting high channel bit error rates. In this project, we will develop a new communication paradigm based on rateless coding, prioritized data protection and transmission, and decentralized data fusion to significantly improve space communications performance.

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.

Research Goals

  • Design integrated rateless codes and rateless transmission protocols appropriate for poorly characterizable wireless channels
  • Design cross-layer strategies to accomplish unequal error control for transmission of prioritized data
  • Design efficient data fusion techniques for signal detection
  • Contribute to the overall science and technology capabilities, higher education and economic development of the Mississippi jurisdiction.


This is a collaborative research project involving The University of Mississippi and Jackson State University in Mississippi, partnership with JPL and Mississippi Space Grant Consortium (MSSGC). Funded by NASA.