Research On The Key Technology Of Mine MIMO Communication System

In our country, the coal resources are mainly concentrated in the underground, which formed the special nature of coal mining work environment:narrow tunnel and limited space environment. Electromagnetic wave spreading in the limited space will produces a lot of reflection, scattering and multipath fading phenomenon. Combined with other factors, the propagation of electromagnetic waves in the mine tunnels is not optimistic. This dissertation analyzes the characteristics of electromagnetic signal and the complex working environment in mine tunnel, and then points out their influence on the establishment of mine wireless communication.In order to establish a wholly mine wireless digital communication system, the primary mission is to solve the problem of multipath fading, but the existing mine communication technology can not solve the trouble fundamentally, which restricting the establishment of mine communication.According to the researches, Multiple Input Multiple Output (MIMO)have made a lot of great progress on the resistance to anti-multipath fading and other technical problems in theory, thus MIMO technology is proposed to solve multipath fading, providing a new technical support to the completion of the mine wireless digital communication system. But limited space environment will cause spatial correlation and bring about performance loss in MIMO system. For this problem, Smart Antenna(SA) with the beam-forming array gain is proposed to make up for the performance loss of MIMO technology with spatial correlation and make it more miniaturized to design antenna array as well.This dissertation firstly analyzes the complexity of underground communication environment, sets up down hole MIMO channel model, compares the performance of the MIMO technology in space-related and non-related cases and highlights the performance loss of the MIMO technology in the situation of space-related. Secondly, from the uplink DOA estimation and downlink beam-forming, demonstrates the Smart Antenna technology in high and low array correlation cases, highlighting the performance loss of Smart Antenna in the situation of low correlation. Finally, summaries the dissimilarity of two technologies in space and antenna structure, and analyses the possibility combination of them. From the perspective of space, this dissertation presents a distributed spatial scheme, and from two aspects of the channel capacity and antenna array space volume, highlights that the combination scheme has better performance in the system and space advantage.