Research of Virtual Channels Scheduling Algorithm Based on Priority in Packet Telemetry System

Consultive Committee for Space Data Systems has designed a group of space communication standards since it is established in 1982, which are now widely used in more than 250 countries and regions[1][2]. Among these standards, TM Space Data Link protocol is a data communication and transmission protocol, which is mainly used in packet telemetry system to transmit packet telemetry data from space to ground[3][4]. In order to better transmit those information, virtual channels scheduling mechanism is widely used in packet telemetry system.Virtual Channels are a group of logic channels formed by dividing the physical channel by time slots. Each virtual channel transmits the packets information with the same or similar service demands, and the physical channel is shared by all these virtual channels. The algorithm used in virtual channels mechanism, namely, virtual channels scheduling algorithm, determines the sequence of occupying the physical channel by each virtual channel, which has a great effect on the transmission efficiency. In this paper, we study the virtual channels scheduling algorithm based on priority in packet telemetry system, and find an interesting conclusion: when the running time of the scheduling module is long enough, for the VC with the highest priority, both the probability of occupying the physical (namely, the VC with the highest priority is scheduled) and the packetslosing rate converge on fixed values, which can provide reference for engineering design.