Research Of Adaptive OFDM Modulation And Demodulation Project Based On Coal Mine Communication

At present, communication under the coal mine is mainly used optical fiber system in china,the system has significant transmitting capacity,low attenuationa and anti-electromagnetic interference,but also in face of high cost, complexly maintenance, site construction difficulties and other disadvantages.It makes great sense to research and design a low-cost,easy installation system which can meet different needs of coal mine communication.Adaptive OFDM technology has high channel utilization, this paper use the ideal of multiuser share a single twisted-pair, propose an adaptive OFDM modulation and demodulation project based on the theory of adaptive OFDM technology and twisted-pair transmission characteristics, to solve coal mine communication problem. The project has the advantage of low-cost, easy installation and maintenance,and satisfy different needs of coal mine communication.This paper present the OFDM communication system based on twisted-pair,and analyze the adaptive allocation algorithm in Multiuser OFDM system,and apply RA algorithm to the twisted- pair system,then design the adaptive OFDM commuication program based on the test parameters and communication distance.In this program, the terminal use the received frame detection head to estimated the communication distance, and select the appropriate modulation parameters to achieve the purpose of communication. After that this paper detailedly design the physical layer modulation and demodulation program,and simulate it in Matlab,then put the simulation data into an arbitrary waveform generator, and test the program on a semi-physical verification platform.The result show that this program not only satisfy the long-distance communications requirements(as far as 15 Km),but also satisfy different transmission rates in mine communication (low-distance bit rate up to 3Mbps, long-distance bit rate up to 307Kbps).The proposed long distance twisted-pair broadband communication system based on adaptive OFDM avoid the disadvantages of optical fiber communication system,and satisfy variation communication requirements in coal mine,it has important directive to the small and medium-sized coal mine communication system construction in our country.