Research Of The Virtual Channels Scheduling Algorithm Based On Advanced Orbiting System

For adapting to the development of space technique and meeting the complex data processing needs of spacecraft,CCSDS developed the Advanced Orbiting Systems (AOS) in 1986.AOS exchanges and processes data in a standardized way, and is able to transmit audio, video, science experiments and many different types of data in a bidirectional way in space links. Currently,AOS plays a more and more important role in aerospace technology field.Virtual channel scheduling strategy is one of the core technologies of AOS. Rational scheduling algorithm is the key to ensure AOS transfer many different types of data in the same physical channel efficiently and orderly. This article researches mainly on the AOS Virtual Channel scheduling algorithm, and the main content includes:First,the frame generation algorithm of broad sense Virtual Channel scheduling is studied.The relationship between the waiting time before completing a frame and the MPDU multiplexing efficiency of isochronous frame generation algorithm,and the average frame generation time of high effiency frame generation algorithm are analyzed.An adaptive frame generation algorithm is also proposed to overcome the disadvantage and shortage of isochronous frame generation algorithm and high effiency frame generation algorithm. The formula of the average frame generation time and MPDU multiplexing efficiency of this algorithm is educed.This algorithm can not only solve the large time delay phenomenon of high efficency frame generation algorithm, but aslo be of higher information transimission rate than that of the conventional frame generation algorithm.Then,the classical virtual channel scheduling algorithms of narrow sense virtual channel scheduling are studied. Through establishing a virtual channel scheduling simulation model, the simulation experiments are put up for the classical virtual channel scheduling algorithms.Based on the simulation results,we get the advantages, disadvantages and application conditions of various classical scheduling algorithms. And, through rigorous theoretical analysis and simulation experiments, the formula of the probability of occupation physical channel and the packet lose rate is first educed at any scheduling time point of the virtual channel which owns the highest priority under the static priority scheduling algorithm.The results can provide a reference for the project implementation.Finally,the virtual channel dynamic scheduling algorithm of Manned spacecraft AOS is studied. On the basis of analyzing the conventional virtual channel scheduling algorithm, a novel AOS virtual channels shelduing algorithm based on frame urgency is proposed, which considers both the time that frames have been waiting for and the maximum time delay that the scheduling module allowed. Through establishing a virtual channel dynamic scheduling simulation model, simulation are performed to compare the performance of the proposed algorithm and the converntional dynamic scheduling algorithm,the simulation results show that the proposed algorithm outperforms the traditional algorithm greatly.