| The centralized multi hop ad hoc network is a multi hop network with central nodes for the whole network scheduling,which breaks through the limitations of the traditional centralized cellular network.With its characteristics of flexible networking,easy expansion and strong anti destruction,it is widely used in military battlefield,emergency communication and other scenarios.At the same time,it has the characteristics of stable control and strong coordination in the industrial wireless transmission with high service quality requirements and has a broad development prospect.However,when omnidirectional antennas are used to communicate in multi hop networks,the reliability and security will be threatened to some extent,and omnidirectional transceiver will cause more interference between multi hop nodes,which will reduce the capacity of the whole system to a certain extent.However,in the current research,the MAC layer protocol design scheme for the multi hop network directional networking mode has many limitations,and its protocol design and development in the actual scene lacks a complete theoretical basis.At the same time,the research on the network performance focuses on the protocol process,lack of detailed module design such as access,maintenance,scheduling and protocol parameters design,and it is difficult to play a role in the engineering development practical guidance.According to the above problems,this paper proposes a directional antenna networking protocol for centralized multi hop network,and describes the key technologies in detail.In order to improve the network capacity in the centralized directional multi hop network,this paper fully considers the interference between nodes and establishes the multiplexing interference model and the MAC layer effective throughput model.On this basis,the protocol parameter design scheme is given under the condition of directional antenna.This paper mainly includes the following three aspects: Firstly,in view of the limitations of omnidirectional antenna used in multi hop network,this paper proposes the MAC layer protocol of centralized directional multi hop network,and specifies the basic elements of the protocol frame structure,system message type,etc.and expounds the key function modules involved in the protocol.In addition,the solution to the inconsistency between the coverage of signaling and service messages sent by directional antenna is given.Secondly,aiming at the problem of node interference in wireless multi hop networks,a random interference model is established by usingPoisson point process,and a hard core Poisson dilution model is constructed according to the protocol interference elimination mechanism and directional antenna characteristics.The number of neighbor maintenance hops and directional antenna are taken as important parameters to quantify the average interference intensity.Then,based on the MAC layer protocol of the centralized multi hop directional network,the system overhead problem in the directional antenna network mode is grasped,and the effective throughput model based on interference is established.According to the delay problem in the process of using directional antenna to join the network,the network access delay model is established,the effective throughput under the constraint of access delay is analyzed,and the optimal value of protocol parameters under the condition of optimal effective throughput is given,which provides the theoretical support of MAC layer for the realization of centralized directional multi hop network.Finally,the MAC layer protocol simulation code is written in the visual studio software,and the directional antenna module is mainly developed,and the key technical modules are simulated and verified to provide the MAC layer program foundation for the realization of the hardware platform. |
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