| With the rapid development of spaceflight technology and in order to meet therequirements of data transmission and management system in complex space mission,CCSDS developed the advanced orbiting system(AOS) based on conventional orbitingsystem(COS) in1986. It is more convenient and flexible for AOS to transmit dataservice and the development of Space Science technology is promoted. At present, theAOS are more and more outstanding in the field of space technology.Virtual channel Multiplexing technology is a key technology of AOS protocol.Virtual channel Multiplexing technology in broad sense includes packet channelMultiplexing technology and virtual channel scheduling algorithm. However, virtualchannel Multiplexing technology in narrow sense only is virtual channel schedulingalgorithm. Virtual channel Multiplexing technology in broad sense is studied in thisthesis, including the research of the packet channel multiplexing process consideringpacket extracting time under finite buffer and the research of the virtual channelscheduling algorithm:First of all, the packet multiplexing technology is analyzed. A high efficiencypacket multiplexing model considering packet extracting time under finite buffer isestablished. Then the recursive formula about the relationship of buffer capability,packet extracting time and buffer overflow probability is given, and simulation on it isconducted. An adaptive packet multiplexing model considering packet extracting timeunder finite buffer is established. Then the recursive formula about the relationship ofbuffer capability, packet extracting time, threshold value and buffer overflowprobability is given, and the recursive formula about the relationship of buffer capability,packet extracting time, threshold value and MPDU multiplexing efficiency is also given.The theoretical formula is compared with simulation data, and simulation results showthat the fitting curves of recursive formula and the simulation are good. So thecorrectness of the recursive formula is verified.Secondly, the virtual channel scheduling algorithm is analyzed. The shortcomingsof the dynamic scheduling algorithm are analyzed, and a virtual channels scheduling algorithm based on frame urgent is proposed. Simulation is performed to compare theperformance of the proposed algorithm with those of the scheduling algorithm withunmovable bundary and the dynamic scheduling algorithm. Experiments show that theproposed algorithm yields much lower scheduling delay, but the scope of application islimitted. So a virtual channels scheduling algorithm based on movable bundary isproposed. Experiments show that the proposed algorithm yields much betterperformance and higher channel utilization ratio than those based on unmovableboundary and dynamic scheduling algorithm in many kinds of sources. |
