Search

In view of Bundle Protocol/Licklider Transmission Protocol ( BP/LTP) stack in delay/disruption tolerant network (DTN), a cross-layer packet-size optimization scheme is proposed in deep space communications. The optimal bundle size, LTP block size and LTP segment size are obtained to minimize the file delivery time in deep space communications, based on the channel bit error rate ( BER), the file size, the channel propogation delay, and the link data rate. The effect of the cross-layer packet sizes on the file delivery time is analyzed, and the cross-layer packet-size optimization scheme is presented. Meanwhile, the impact of the channel BER, the file size, the channel propogation delay, and the link data rate on the optimal LTP segment size is simulated and analyzed, as well as the performance gains of the cross-layer packet-size optimization scheme. The theoretical analysis and simulation results indicate that the proposed scheme can optimize the cross-layer packet sizes under certain space missions and circumstances, which effectively improves the throughputs over the scheme with the common packet sizes. [ABSTRACT FROM AUTHOR]

Abstract:In Mars exploration missions, due to the long propagation distance and planet occullation in rovers-to-Earth direct link, dala transmission suffers a huge loss and frequent interruptions in connectivity. Based on delay tolerant network (DTN) framework, a distributed systematic Raptor coding (DSRC) scheme is proposed for the multi-hop relay transmission data through an orbiter to Earth communications scenario. A simplified joint decoding scheme is designed, and the asymptotic performance of DSRC scheme is analyzed. Moreover, the improved DSKC scheme is optimized for the finite code-length. Simulation results show that the DSRC scheme can achieve a decoding failure rate of 0. 01 with a decoding overhead of 5%, which outperforms the existing distributed raleless erasure codes. [ABSTRACT FROM AUTHOR]

By using the noise temperature of deep space Ka-band channel，a two-state Gilbert-Elliot channel model is designed to capture the quality of the channel that randomly ranging from good to bad state. Moreover, the downlink of deep-space communications can only receive delayed channel state information (CSI) feedback. Combining the theory of the partially observable markov decision processes, an optimal transmission scheme has been developed over the delayed CSI feedback. The key thresholds for selecting the optimal transmission method in the deep-space communication environment are derived，and the simplified closed solutions are given. Simulation results of Earth-to-Mars parameters show that the proposed scheme can increase system throughput and improve transmission efficiency. [ABSTRACT FROM AUTHOR]

The performance can be degraded when traditional LT (Luby Transform) codes are used for deep space communications. In this paper the systematic LT codes are designed by reconstructing the bipartite graph and can be suitable for deep space communication environment. An encoding algorithm to eliminate cycles is proposed. The convergence threshold of the systematic LT codes is analyzed by using extrinsic information transfer chart. And then the performance of systematic LT codes is evaluated through a serial of simulation experiments. Simulations results show that the systematic LT codes adopting the proposed encoding algorithm can significantly degrade the error floor and improve the decoding algorithm performance. [ABSTRACT FROM AUTHOR]