Relay Selection And Power Allocation For Cooperative Communication In Underground Tunnels

The wireless communication system in underground tunnel is very complex. Since the antenna beam is too wide to communicate with each other in tunnel, and with so many impact factors such as the limit of tunnel space and the tunnel wall. The electromagnetic waves that the receiver receives from the sender, it suffered the refracted and reflection and the directly transmission. These phenomena caused the multipath fading. The multipath fading sincerely affected the quality of communication in underground tunnel. Moreover the fading in underground tunnel more severe than land, where depth of the fast fading up to 30 ~ 40 d B. In order to resolve the multipath fading problems, cooperation communication is proposed based on the MIMO technique. It overcomes the space limitations to install the multi-antenna of MIMO system in tunnel. Cooperative technique can obtain the diversity gain similar to the MIMO system through a single antenna. In multi-user environment, the use of a single antenna in a certain way that share the antenna with each other at the mobile station to produce a virtual MIMO antenna system to obtain diversity gain. Therefore, under the best channel tunnel conditions, relay selection and power allocation of cooperative communication in mine environment for solving multi-path fading plays a very important role to solve the problems and has a practical significance in society.Firstly, we focus on the instruction of the existing wireless communication systems in underground tunnel; tunnel channel conditions; cooperative communication and its relay selection and power allocation are summarized. For solve the disadvantage of the signal transmission, we focus on enlarge the original channel tunnel model range from the near place to far place, the multi-mode channel that combined the GO(Geometrical Optical) model and FW(Full Wave) model is proposed.Secondly, based on the existing study of cooperative communication in tunnel environment, under the condition of multi-mode channel, the relay selection and power allocation in cooperative communication is studied and analyzed. The optimal relay assignment strategy and simpler relay assignment and optimal power allocation are proposed. All that problems are based on the capacity and the outage probability in communication progress.Finally, under the condition of the multi-mode channel and the cooperative communication model in tunnel, the analyze of the channel capacity and the outage probability through different relay location and power allocation, the joint relay selec-tion and power allocation method is proposed. The method based on the best relay selection that makes the maximize channel capacity. And under this condition the method of the optimal power allocation is proposed. Its purpose is to make the outage probability minimize. We use Matlab to simulation the research results. The results showed that effective relay selection and power allocation method in cooperative communication in tunnel can solve the multipath channel fading problem effectively.