Research On MAC Protocols Of Self-Organizing Networks In Small Satellite Constellation

As the spacecraft becoming more and more complex, the cost and risk of producing single big satellite increases, and gradually becomes the bottleneck of the development in space career. Therefore, scientists suggest that some small satellites construct a constellation network, cooperating to support the signal processing, communication and payload experiments in space. This method can not only implement the full functions of the single big satellites, and reduce the cost and risk, but also improve the total coverage of earth, shorten the aceess period, and simplify the update and maintenance operation. Using this method, we can fulfill the space mission better. Aiming at the key problem in small satellite self organization network, the single point failure problem and the special application scene in space environment are analyzed, and a master-slave heterogenous MAC protocol in the self organization network of the small satellite constellation - 3D-MAC protocol is proposed. This protocol is implemented in the prototype system, and its networking performance is tested and optimized. The contributions of this thesis are as followed:Firstly, the development history and the categories of MAC protocol in wireless ad hoc network are introduced briefly. Based on the development hiberarchy of small satellite technology, some famous comercial network systems using small satellites are listed, and a review of some typical self organization networking protocols in the small satellite constellation is given, along with the improvement measures to these protocols.Secondly, the self-organizing networking problems of the master-salve heterogenous modems are analysed, such as network self-construction problem, network rebuilding problem caused by master node failure and media acess scheduling problem. Aiming at these problems, a distributed, beacon based, master-slave heterogenous and asynchronous self-organizating MAC protocol - 3D-MAC protocol is proposed, with three corresponding solutions which are node division cluster head variable scheme, round division selection scheme and time division preserved random media access scheme.Thirdly, the design idea, processing flow, statemachine design and message format design of 3D-MAC protocol are provided in this paper. With high stability, robustness and flexibility, by using our protocol, the survival ability of the small satellite constellation network in adverse space environment improved.Finally, a self organization network prototype system of the small satellite constellation is designed and implemented based on the satellite communication modem MHX 2420. With the prototype system, the correctness and robustness of our self organization networking MAC protocol is validated. By analyzing the test results, the networking performance of our prototype system is optimized, and a set of parameter values which can provide best networking performance is obtained.