Channel covariance modeling for multi-user MIMO systems

Because of the rapid variation in channel state information in multi-user networks with mobile nodes or scatterers, it is difficult both to maintain high communication performance using multi-user multiple-input multiple-output signaling and to create channel models that effectively represent the proper relationship between channels to different users as a function of their relative position. This paper uses the channel covariance matrix as a means to mitigate these problems. First, the paper discusses the use of channel covariance for signaling in the multi-user broadcast channel, and shows how to use conventional covariance models to dramatically reduce the required feedback complexity while maintaining good performance. The paper then focuses attention on the modeling of multi-user channels by exploring the position-dependent properties of the covariance using an analytical framework.