Research On Data Link Layer Protocols And Network Layer Protocols For Underwater Directional Wireless Sensor Networks

Underwater wireless sensor networks have a very important role in marine resources exploitation.It is an urgent task to improve the performance of the network.Meanwhile,directional communication has an advantage of spatial reuse,which can be used to improve some performances,such as network throughput and the success rate of transmission.This thesis designs several kinds of MAC protocols and route protocols,which are suitable for directional underwater wireless sensor networks,improving the performance of network.Firstly,this thesis builds up directional transmitting model and receiving model,separately basing on the principle and work mode of modal projectors and vector hydrophones.As for directional transmiting model,to select the optimal beam pattern,the thesis defines a function of area ratio of outside and inside transmission,which can be used to measure the superiority of beam patterns,and uses the particle swarm optimization to obtain the optimal solution of that function.As for directional receiving model,referring to the direction-finding and electrical rotation working mode of vector hydrophone,this thesis designs the flow of masking interference signal.It can directionally receive one signal coming from one direction,alleviating the disruption of interference signals coming from other directions.As for how to select the optimal electrical ratating direction of vector hydrophone,the thesis proposes a scheme which is to use the particle swarm optimization to obtain the optimal electrical rotating direction of vector hydrophone,through which the signal-to-interference ratio can be the largest.Secondly,as for the MAC protocol,regarding the omni-directional ALOHA(O-ALOHA)protocol as the starting point,the thesis gradually proposes directional ALOHA(D-ALOHA)protocol,directional MACAW(D-MACAW)protocol.The work contains designing the flow of these two protocols and improving the virtual carrier sensing(VCS)mechanism.Simulation results suggest that the D-ALOHA protocol can obtain a better network throughput and success rate of transmission than O-ALOHA,owing to its advantage of spatial reuse.And the D-MACAW protocol can alleviate the hidden terminal problem appearing in the D-ALOHA protocol,especially when data packets are long.Furthermore,the impact of random rotation of node on the performance of D-MACAW protocol,resulting from the disturbance of water current,was analysed through simulation.And the solution is proposed in the thesis.Finally,the thesis focuses on some research work on route protocols for directional underwater networks,and designs the implementation scheme for the minimal interfering cost based AODV protocol.Some comparasion work between this protocol and the minimal hop number based AODV protocol has been done.Simulation results show that the former protocol has a higher success rate of transmission and network throughput than the later protocol in the directional underwater sensor networks.