Multiple-input multiple-output eigenbeam space division multiplexing in time-varying channel: Tolerance of time-varying channel and application of channel prediction technique

Degraded communication performance due to feedback delay is recognized in multiple-input multiple-output (MIMO) eigenbeam space-division multiplexing (E-SDM) in time-varying channels. The degree of performance degradation differs depending on the MIMO reception technique used. The degree of degradation in cases where spatial filtering techniques such as the zero-forcing (ZF) technique or the minimum mean square error (MMSE) technique are used is recognized to be lower than the degradation that occurs when the singular value decomposition (SVD) technique, which determines the reception weight matrix based on the left singular matrix of the channel matrix, is used. In this study, the communication performance in time-varying channels of each of these reception techniques was compared using a system model based on the IEEE 802.11ac standard. As a result, it was found that the performance in the case where an improved SVD technique was used, in which the channel state information at the receiver (CSIR) is equal to the channel state information at the transmitter (CSIT) that is transmitted by feedback, was better than the case where the ZF technique was used, and was similar to the performance in the case where the MMSE technique was used. These results disprove the traditional assumption regarding the degree of performance degradation associated with these techniques. In addition, a method was proposed for use of channel prediction with the improved SVD technique, and showed that the performance of the proposed method was almost equal to that in the case where a spatial filtering technique was used with channel prediction. The result showed that a SVD technique was one of the strong choices of the MIMO reception technique in time-varying channels.