Robust Grassmannian prediction for limited feedback multiuser MIMO systems

In this paper, we propose a robust Grassmannian prediction algorithm to provide channel state information (CSI) at the base station for multiuser multiple-input multiple-output (MIMO) systems with delayed limited feedback. The underlying coherence among adjacent quantized CSIs is fully exploited to achieve robustness against the quantization error caused by the limited feedback. Rather than sticking to the nonlinear manifold, we derive that, using the locally Euclidean property of Grassmannian manifolds, the prediction can be obtained by solving a simple linear system in the embedding vector space. Numerical results show that the proposed algorithm is less sensitive to the quantization residual error and thus improves the achievable sum rate while keeping the amount of feedback to a practically low level.