Throughput Modeling And Busy-Tone Based MAC Protocol Designing For Wireless Ad Hoc Networks With Directional Antennas

Due to its independence of fixed infrastructure,quick networking,and strong anti-destroying,wireless ad hoc networks have been widely used in the field of military and civil communications.Researchers take directional antenna technology into the wireless ad hoc network,which effectively reducing the signal collisions and improving spatial reuse and saturation throughput of the networks.However,what is the effect on saturation throughput when the data collision caused by deafness problem and directional hidden terminal problem? How to model and analyze the saturation throughput of the random access protocol of the directional wireless ad hoc networks? How to further reduce the collision and improve the performance of saturation throughput? The existing research work has not been able to give a completely satisfactory answer.Research work of this thesis is focusing on the above issues,the main innovative achievements include:(1)We propose a directional random access protocol saturation throughput model.In this thesis,we first analyze the collision of data transmission caused by deafness problem and directional hidden terminal problem in wireless ad hoc networks with directional antennas.Then,we propose a saturation throughput model based on Markov chain for typically directional random access protocol(D-MAC),which provides a theoretical basis for optimizing the performance of directional medium access control.The model calculates the theoretical value of saturation throughput by calculating the transmission probability and collision probability in a randomly chosen slot time and in a randomly chosen direction.Based on this model,this thesis analyzes the influence of directional antenna beam number,node number,the value of the backoff contention window and other parameters on the total network throughput,and focuses on the differences of saturation throughput of different traffic flows which caused by the collision of data transmission under the given network topology.The comparison between the simulation results and the numerical results shows the effectiveness of the model.(2)We propose a MAC protocol based on busy tone for ad hoc networks with directional antennas.The protocol uses the busy tone assistant strategy to avoid the collision of data transmission caused by the deafness problem and directional hidden terminal problem.The node completes the directional beam alignment by sending the omni-directional RTS frame and the directional CTS frame.During the data transmission process,the sending node and the receiving node avoid the data collision by sending the "transmit busy tone" and the "receive busy tone" directionally.Through multi-beam directional sending the "deaf busy tone" to avoid the data retransmission and the unfairness between the throughputs of multiple links and to achieve concurrent directional data transmission based on busy tone detection.Simulation results under a variety of network topologies show that the proposed protocol can effectively avoid the collisions caused by the deafness problem and the directional hidden terminal problem.The link fairness and the network throughput performance are superior to the traditional directional busy tone auxiliary channel access control protocol.