A Study On MAC Protocol With Collision Control For Self-organizing Emergency Communication Network

As a special communication mechanism to ensure that people respond to emergencies,emergency communications may be faced with the problem that the communication area,scale and the degree damage of equipment is difficult to prediect.In recent years,the mobile Ad Hoc networks as a distributed network has become an important means to support emergency communications because of its rapid network formation,and strong resistance to destruction.At the same time,the quality of the MAC protocol can directly affect the communication quality and efficiency of building a network in the emergency communication s,and then affect the emergency command and rescue work.Therefore,it is very important to discuss and study the MAC protocol in self-organizing emergency communication.In this thesis,it focuses on transmission collision control from channel access control and data transfer to enhance the network performance.On the one hand,for the coexistence of priority and ordinary users in emergency communications,according to the hidden terminal and blocking problems existing in channel reservation strategy,a MAC protocol based on dynamic space reservation strategy is proposed for emergency communication scenarios.Firstly,a set of emergency command vehicles,distributed in the networkarea,periodically schedule the sending or receiving of data on the channel,based on transmission requests from singlesoldier systems.Secondly,the space reservation radius of the priority user is dynamically determined using the instantaneous node density of the network and the node interference range.In addition,based on the Markov chain model and knowledge of probability theory,the collision probability of packets and the throughput of system are analyzed theoretically from the perspective of mathematics,and the correctness of the assessment is further verified by simulation.The results show that the dynamic space reservation strategy can effectively alleviate the packet transmission collision problem,and greatly improve the system throughput and the effectiveness of important message transmission.On the other hand,for situations where people are not easy to intervene,the existing emergency communication systems can only operate in accordance with a predetermined plan,lack the ability of self-adaption and self-learning,it has the problem of poor communication efficiency and difficulty in meeting diverse communication needs.and other issues.Therefore,a strategy of channel rendezvous establishment based on capture effect with cognitive ability is proposed.First of all,according to the cognitive,intelligent and adaptive characteristics of cognitive radio technology,the use of channels in self-organized emergency communications networks is perceived and classified.Secondly,the channel acquisition probability is calculated through neighbor distance sensing and location confirmation.When multiple nodes compete for the same channel,the success rate of channel access is improved by comparing the channel acquisition probability of each node.The simulation results show that adopting the channel access method based on the capture effect in the cognitive self-organizing emergency communication system can effectively improve the reliability of the emergency communication service.