MIMO Capacity in a Pedestrian Passageway Tunnel Excited by an Outside Antenna

Numerous papers have already been published on the improvement of the channel capacity which can be obtained by using Multiple Input Multiple Output techniques. Various environments have been studied as indoor and urban environment. Since there is also a need to cover tunnels, recent works deal with the characterization of the channel transfer matrix in order to predict the performance of the link in such a configuration. However it was always assumed that both the transmitting antenna and the receiving antenna are situated inside the tunnel. Since, for short tunnels, an additional fixed antenna inside the tunnel is not always necessary, the objective of this paper is to examine the case of a mobile entering and moving inside a tunnel excited by an outside antenna. Since the capacity depends both on the path loss and on the correlation between array elements, a parametric study shows the influence of the offset angle characterizing the direction of the fixed antenna array referred to the tunnel axis. Results are based on experiments carried out in a pedestrian tunnel and at a frequency of 2.45 GHz. Key-Words: MIMO, tunnel, capacity, angular spread, correlation.