Principal component analysis based multiplexing solution for MIMO systems in high-speed railway

In order to enable reliable spatial multiplexing transmission, an environment with rich scatterers is often required, which is not equipped in most railway running environment. So the MIMO channel with sparse scatterer and dominant LOS component in high-speed railway scenario is usually strongly spatial correlated and often fails to support a multiplexing transmission link. While it is actually not a pure LOS environment even in open plain or on a viaduct according to the existing engineering measurements. Hence, in high-speed railway environment, it is still highly possible to support partial multiplexing transmission if configuring a reasonable antenna placement structure with adequate antennas along the train body in the future. To target this problem, this paper investigates the solution of reconstructing the highly correlated railway channel into an equivalent channel with less correlation using the method of principal component analysis and thereon proposes an optimal partial multiplexing transmission solution to improve the link performance. With the proposed solution, the capacity in the distant area from the base station is verified to be significantly improved and that in close distance area is maintained meanwhile the condition number is reduced to be less than 10 to meet the required link quality.