Expected Capacity Enhancement in Subway Tunnels with MIMO Techniques

Extensive works are now undertaking to study the improvement of the channel capacity when using a multiple array of transmitting and receiving antennas. Nevertheless, the capacity is strongly dependent on the correlation between the various channels and extensive measurements are needed to characterize this correlation. In this paper, we consider the case of a subway tunnel and a carrier frequency of about 900 MHz (GSM-R), which has been adopted for the European railway digital radiocommunication systems. After a brief presentation of the channel sounder, the main characteristics of a SISO channel, such as the power delay profile, are given. Then, considering a system of 4x4 antennas, the spatial power correlation at the base and mobile stations is calculated. Lastly, from the eigenvalue decomposition of the transfer matrix, the channel capacity is deduced and compared to the capacity calculated by assuming i.i.d. Rayleigh channels. I