Channel Simulator Designed For Deep Space Communications

With the ever-increasing of the deep space exploration, the requirements of transferring data and files are also increasing in deep space communications. Since the deep space network has some unique characteristics, like high delay, long propagation distance, high energy loss and frequent link disruptions, obviously, it also put a higher demand for stability of deep space communications system. Due to the high cost and difficulties that to schedule the experiments on a true practical deep-space communication system, there is an urgent need to establish a file transfer simulation system to satisfy the characteristics of deep-space communications. For the above reasons, this paper designs a system based on the point-to-point transmission for deep space communications, proposes an adaptive flow control mechanism based on virtual instrument technology, then tests deferred NAK CFDP on the simulation platform and provides some simulation results.In this paper, we first analyze the relevant characteristics and some key technologies in deep space communications system, obtained the key issues which need to be considered in the simulation platform design such as frequent link disruptions and high error rate. From this, we designed a Mars to Earth communication link simulation platform programs which including four simulation sub-modules, divided and achieved the function of each module. Then, based on the need to simulate real-life scenarios, we designed and implemented a method about adaptive flow control and time delay control, which can adjust transmission rate to the channel environment parameters in deep space channel simulator. Finally, we introduced CFDP protocol, discussed the transmission mechanism and delay of CFDP in Deferred NAK Mode, then tested it on the simulation platform.Analysis of the simulation results proved the reliability and practicality of this simulation platform in file and data transmission in deep space. The adaptive flow control in channel simulator improved the data outstanding throughput, while the simulation result of Deferred NAK CFDP showed the reliability and good performance in deep space file transmission.