Link Layer Design And Implementation Of Point To Multipoint Microwave Communication System Based On TDMA

This paper gives the design and implementation of link layer based on TDMA to meet the demand of the frontier and island to the point to multipoint microwave communication system. Firstly, This paper introduces the present situation of PMP microwave communication system at home and abroad, link layer concept, function and structure of the PMP microwave communication system, and analyzes the meaning of the link layer design and implementation.This paper analyzes the link layer design platform demand of MCU+FPGA based on Software Defined Radio, gives the requirements of link layer design index, and presents a hardware platform design, frame structure design, networking arithmetic, switching method, channel allocation strategy. Relying on the actual product environment, the system demand system design, product realization of software and hardware, the system test and product release were introduced.According to the function demands of the PMP microwave communication system link layer, gives the system mainly functions and modules of the design and implementation, and in the design of frame structure, network strategy and bandwidth allocation the paper makes the detailed analysis and elaboration.Finally, we prove this design in a PMP microwave communication system. The case of the network capacity, access of user station, user operation access and service delay requirements are verified. The test proved the design of link layer can meet the requirements of the system completely. The following key issues are solved in this paper:First, the design of reconfigurable hardware platform based on microcontroller C8051F130 and FPGAEP2C35F484;Second, the uplink and downlink symmetrical frame structure design based on the 64kbsp distribution, according to the requirements of user characteristics and network;Third, the practical and efficient link layer design to complete user station access, multiplexing, switching and wireless channel adapter divides the hardware and software function modules, and defines function and task of each module.The PMP support networking equipment quantity 1 central station and up to 32 user stations, for star network. The subscriber station can be random access, communication distance up to 50 km.The equipment use FDD duplex mode, TDM downlink, TDMA uplink.Support 60 duplex 64kbps wireless channel, channel allocation minimum size 64kbps.The transmission delay of the is not more than 8ms.The equipment support integrated service access and transmission, included telephone, magneto telephone, asynchronous data of 1.2k-9.6K,synchronization K interface data of 8k-128kbps,128k-1024kbps IP data and the El transparent transmission service. It supports up to 128 users, the highest rate of 4Mbps data together. Telephone service can be divided into high priority users and general users, channel distribution according to need. Fixed distribution the remaining channel; E1 transparent transmission can support scheduling. Each subscriber station supports 8 telephones for local exchange, not need to occupy the wireless channel resources.The device can be fixed installed, can also be equipped with motor. It effectively solves the problem of user, which is in frontier, island and mountain plateau where is not convenient for cable erection of professional network.