Design And Implement MAC Protocol Of Adaptive Trunked Communication System

Mobile trunked communication system,a kind of specific communication network whose base station can be moved,has been widely used in dispatching systems such as public security, mitigating disasters, construction by transmiting voice, data and video.The number of its users is less than common communication system, but its coverage is larger.To solve the problem that trunked communication system exited fail to provide broadband service for nearby users and protect the communication quality for remote users at the same time,we design a new one.Our system can meet different requirements of different users,who may be nearby or remote to the base station, and adapt to the rugged terrain well.According to the need, our system can adjust power output and bandwidth of channel dynamically.The air interface of mobile trunked communication system is divided into physical layer(PHY), data link layer(L2) and radio resource control layer(RRC).And L2 layer is divided into medium access control layer(MAC), radio link control layer(RLC), packet data convergence layer(PDCP).This paper mainly focus on the MAC layer in technology of broadwidth adaptive and coordinate other protocol layers of the air interface to implement the adaptive scheduling of the physical source.After studying LTE protocol and TETRA protocol,we design a new MAC layer protocol,which will be applies to the adaptive scheduling on wireless source, and a processing mechanism which is used to switch to broadband or narrowband and control the transmission on shared channel and common channe.After programming four transmission blocks and structuring test samples,we use NS2 to verify and test our system.The results showed that our system can complete the expected function and improve performance.