Design And Implementation Of A MAC Protocol In Satellite Ad-Hoc Networks

Satellite Ad-Hoc network is a kind of wireless communication network,in this network,various small satellites fly around the earth in the same orbit cycle and complete the set space flight missions,the communication between small satellites is self-organized through the distributed protocol and without access point's support.due to its low cost,small risk,survival ability strong,can use the new technology faster and meet the need of network centric warfare,it can well solve the single large satellite problems such as high cost,high risk and have broad application prospects.the performance of a network's MAC protocol directly affect the efficiency of the wireless channel resources utilization and the performance of the network.therefore,the research of satellite Ad-Hoc networks' MAC protocol is of great significance.This paper introduced,compared,analyzed the several MAC protocols popular in current ground mobile Ad-Hoc networks,according to the difference between satellite Ad-Hoc networks and ground mobile Ad-Hoc networks,put forward the problems of directly using the several mainstream MAC protocols to satellite Ad-Hoc networks.then to solve these problems,this paper proposes a satellite Ad-Hoc networks' MAC protocol based on TDMA--SAHN-MAC(Satellite Ad-Hoc Networks MAC)protocol.the protocol,using the big propagation delay of satellite Ad-Hoc networks,according to the case that the propagation delay greater than the transmission delay,the node of sending data frame is in sending data frame,the node of receiving data frame free,the receiving node is in receiving data frame,the sending node free,put forward the mechanism of sending to each other,namely the sending node and the receiving node send a data frame to the other party and receive from the other party at the same time.to cooperate with the mechanism of sending to each other,the authors put forward time slot allocation mechanism for link and a new time slot allocation scheme.at the same time using satellite Ad-Hoc networks' characteristics of node number less,less hop,the network scale small,the author also proposed the new time synchronization scheme,under the scheme,all node in the network will periodically update the propagation delay with other nodes,and according to the relationship between the propagation delay and the transmission delay,decide whether to adopt the mechanism of sending to each other,realize the flexible switching between single node sending mechanism and the mechanism of sending to each other.Geared to the needs of practical application platform,to assess the performance efficiency of the SAHN-MAC protocol,the author designed and implemented a MAC protocol simulation test software based on discrete event simulation mechanism,and simulated the SAHN-MAC protocol under different scenarios,compared and analyzed the performance efficiency of the SAHN-MAC protocol and the SSFN-MAC(Small Satellite Flying Network MAC)protocol.the simulation results show that the SAHN-MAC protocol's suitable scene is the satellite Ad-Hoc networks that the propagation delay of network is closed relatively,the transmission delay is less than and closed to the smallest propagation delay.the SAHN-MAC protocol can do well in terms of throughput performance and meets the design goal of this paper.