Simulation And Research Of PSLP、SCPS Based On Visualsim Platform

CCSDS (Consultative Committee for Space Data Systems) formulated some series of standard and suggestions, and PSLP(Proximity-1Space Link Protocol)、SCPS(Space Communication Protocol Specification) are two of them. PSLP is a data link protocol which is used among equipments such as prober, lander, rovers, orbiter and orbit repeater. SCPS is a series of communication protocol extended from TCP/IP, which is more adapted to the environment of space communications compared with TCP/IP. This thesis focuses on the research of PSLP、SCPS-NP and SCPS-TP, building modules of these protocols and simulation platform of communication system between earth and lunar on VisualSim platform. In addition, this thesis researches the congestion control algorithms in the space communication environment.The main contributions of this thesis can be summarized as two points:Firstly, PSLP、SCPS-NP (Space Communication Protocol Specification-Network Protocol) and SCPS-TP (Space Communication Protocol Specification-Transport Protocol) are studied, the modules of these protocols and the simulation scenarios are set up, and finally simulation platform of communication system between earth and lunar are built in this thesis. The main functions of the simulation platform consists of three parts:the COP-P (Communication Operations Procedure for Proximity links), the establishment and termination of the link session in data link layer; supporting point-to-point routing and flooding routing, supporting unicast, multicast and broadcast in network layer; connection establishment and termination, supporting header compression, SNACK and Vegas algorithm in transport layer. Routing algorithms and congestion algorithms could be simulated and researched on the simulation platform of communication system between earth and lunar.Secondly, the congestion control algorithms in space communication networks are researched, and a improved Vegas algorithm is proposed. Vegas algorithm is a method which makes channel estimation based on RTT to control congestion, and the performance of Vegas is not ideal in long delay and high error rate environment. This thesis proposes a improved Vegas algorithm based on bandwidth allocation, which could reach the network available bandwidth more quickly and get better performance than Vegas. The simulation results show that the improved Vegas algorithm could achieve higher transmission rates than Vegas when the RTT is greater than500ms and could ensure the fairness among connections.