Wideband Wireless Communications Techniques Application Research In The Coal Mine Tunnel

Mine tunnel is different from the transmission characteristics of terrestrial free-space channel, which is limited to space radio channel.Diversity technique is one of the most effective methods to solve the free-space multipath fading.How to solve this problem of the mine channel by applying it is the theme of this paper.This paper has analyzed the fading characteristics of multipath transmission in the typical model of mine channel.Typically speaking, fast fading form, strong electromagnetic interference is both the main feature.According to the channel characteristics of mine, this paper has combined the adaptive beam forming techniques with the OFDM system which is applied to mine wireless communication, and then a mine Adaptive OFDM system has formed.After analyzing and comparing the methods of realization of existing systems, the POST-FFT method may be more adaptable to the mine channel environments.Because the receiving signal can restore the transmitted signal to better after being weighted with FFT. Herein Weight vector in this generation is the key for realization.As channel estimation algorithm based on time-domain training sequence has the characteristics of fewer Fourier transform and less computation, the weight vector generation algorithm is suitable for the Mine Adaptive OFDM systems.The mine channel of limited space has spatial correlation, and the requirement of Space-time Coding based on multi-antenna techniques for diversity gain is not spatial related with the independent channels, which is a barrier. In this article,the Eigen Beam forming technique shaping transmission signal in the mine channel will be discussed, that is, the Mine STEBC(Space Time Eigen Beam Coding) technology structure is formed to make the mine channel uncorrelated and reduce the channel estimation computational complexity. Finally, abiding by the system optimization ideas, this article has combined the two technologies to form the Mine OFDM-STEBC system by fusing of these two techniques, and an overall designation was made at the same time.Simulation results shows that the new technical system can inhibit the transmission fading of multipath single, and can obtain diversity gain respectively from the domain of frequency, time and space, then the mine communication system performance was upgraded greatly.