Research On MAC Protocol In Buoy Satellite Communication System

Future underwater information network with communication,remote control,data acquisition,early warning and other functions,can collect the underwater environmental information characteristic data and ensure the underwater communication system to operate effectively.Air-sea integrated sensing communication network based on space-based information network can effectively enhance information detection capability in marine environment,to meet the future needs of the marine information network transmission system capacity applications.Improving satellite access capability of buoy satellite communication system based on small satellite access is the key technology of enhancing the effective uploading of underwater detection and early warning information.But because the buoy satellite access system MAC protocol design by the satellite communication channel and sensor network traffic double limit,faced with contradictions between large-capacity users and limited channel resources,needs to meet the transmission needs of a variety of types of information,conventional satellite access protocols are not well suited for buoy satellite systems.Based on OPNET,we design the system model of buoy satellite access system,including satellite orbit model,satellite coverage scene model,buoy satellite physical layer transmission model,buoy node model,satellite node model.This paper introduces the application of OPNET network simulation platform,including OPNET three-layer model domain,sub-domain,node domain,process domain,and OPNET modeling mechanism,event-based modeling mechanism,package interaction-based modeling mechanism.We propose a multi-service fusion scheme for dual-channel buoy satellite systems based on TDMA.We design a super-frame structure suitable for multi-service convergence and an open-loop time synchronization scheme based on location information,and use OPNET to design the model of buoy satellite nodes.We propose a time slot assignment protocol based on location information,which can effectively improve the performance of single channel and dual channel in buoy satellite access system.We propose an improved fixed-contention access protocol to achieve maximum channel utilization and shortest delay in a competitive access protocol under different loads.We propose a back-off algorithm and multi-packet processing scheme when reserving access under the unstable load of massive floating buoys,which can effectively reduce the collision and improve the channel utilization rate.