Study On The Theory Of Radio Propagation And The Key Technologies Of MIMO Channel Model In Mine Tunnel

Electromagnetic waves will be attenuated greatly by the wall in mine tunnels, mostly come into multi-path because of continual reflections and dispersions. It is still a hard work to study the characteristics of Electromagnetic waves propagation in tunnels in the field of wireless communication. Wave-mode theory is going to study the large-scale fading and geometrical optics to the small-scale fading and build the MIMO channel model of wireless channel in tunnel in our work, considering their personal strongpoint.Medium-guide multi wave-mode theory is advanced from wave-mode theory during studying large-scale fading in our work.(1) Higher-mode loss formula owing to medium-guide, surface roughness, tilt, corner and antenna insertion are deduced.(2) Calculate the number of wave-modes in tunnels.(3)Various loss of above (1) covering overall modes is formularized because the fading is the result of not only fundamental mode but also every higher modes.(4) Medium-guide loss is converging to a value with increasing frequency. (5)Optimal frequency of propagation in tunnel is proposed by formula and tables according to the parameter of roughness and tilt. The simulation is well consistent with the experiment data of some conferences, about propagation fading and field strength distribution.The Tent Law theory part of geometrical optics is to analyze the small-scale fading of wireless channel. (1) Define the 3rd Tent Law to vector model from scalar model. (2)Build MIMO channel model in mine tunnel. (3) Formularize the correlation of MIMO channel of tunnel. By simulating according to above, azimuth spread is small, and power is close to the Laplacian distribution, in other words, propagation is directional strongly. Channel correlation has close relations with the placement of antenna array, which optimal placement is perpendicular to the axis of tunnel, and the correlation taken for zero with space between antennas to10l .Simulation of theory answers for the measured data.The effective sub channels are provided on condition of low correlation which requires enough space between antenna array elements of MIMO. Then it is a key that cross section of mine tunnel is large enough filled with antenna array. The eigen-mode theory is to analyze degrees of freedom provided by the tunnel space taking no account of engineering, thereby bring forward a formula calculating the degrees of freedom in tunnel which is the upper limit of MIMO capacity in tunnels. Tunnel space can provide some freedoms with designing communication volume reasonably. Degrees of freedom can reach to 3 with distance of 300 meters.