Limited feedback precoding performance analysis for train-to-wayside communications in subway tunnels

Multiple-input multiple-output (MIMO) techniques have proven their potentiality for efficient transmissions in the public transport domain even in specific propagation context such as tunnels. When perfect channel state information (CSI) is available at the transmitter, performance improvement can be achieved through a precoding operation. However, the performance of closed-loop MIMO system depends on the spatial correlation of the channel, the quantity and the quality of the CSI at transmitter. Limited feedback precoding is one of the features used by LTE to improve performance in a MIMO channel. This technique is confirmed in several standards (LTE-A, 802.16e...). Here, we focus on the performance of quantized precoding in coded MIMO systems in subway tunnels. Channel measurements obtained from a 4×4 MIMO channel sounding are used to emulate the channel in the system simulations. A performance comparison between different well-known limited feedback precoders: max-d_min, P-OSM and LTE is performed and their strength to channel correlation is investigated. This study reveals that the last one is more resistant with low complexity in real subway channel.