| On-board processing (OBP) is one of significant satellite communication technologies. The Asynchronous Transfer Mode (ATM) is widely used in the OBP.Firstly, several key technologies used in the current OBP systems are analyzed in this paper. Under the condition of a GEO satellite system, a suitable OBP system based on ATM switch is proposed, and a method of multiple address access fit to the ATM switch communication system is discussed. In this ATM system, the network protocol format, the internal format of the cells, the structure of the switch fabric unit and the I/O interfaces are designed respectively. An improved CAC (Call Admission Control) algorithm is presented. The computer simulation results show that the new algorithm can improve the statistical multiplexing gain, link utilization, cell loss rate and the number of resources which can be linked to the system. These good performances are more suited to satellite ATM switching systems. The main problems are analyzed and some solutions including some programs are developed when TCP is applied to the satellite communication. Under the LEO satellites network of the Iridium-liked system environment, five TCP congestion control strategies including the Tahoe, Reno, Newreno, Sack and Vegas are discussed. The simulation results show that the Vegas can be used to predict congestion conditions correctly and its congestion window (cwnd) control is smoother. This paper's study work has better reference value for on-board processing and on-board switching in satellite communication systems. |
