Dynamic Channel Feedback Control for Limited-Feedback Multi-User MIMO Systems

Efficient channel feedback methods are becoming more important in limited-feedback multi-user multiple input multiple output (MU-MIMO) systems. We propose a new dynamic channel feedback control (DEFCON) scheme, which efficiently allocates the limited system resources for channel feedback to appropriate users. The main features of the proposed DEFCON scheme are as follows. Firstly, the channel feedback procedure is composed of two stages: rough channel feedback of all users and additional precise channel feedback of the selected users only. Secondly, each selected user is allocated with different amount of resources for additional channel feedback according to its channel status. We mathematically solve the resource allocation problem by proposing a suboptimal method, which utilizes convex optimization technique combined with iterative steepest decent direction search algorithm. Numerical results show that zero-forcing beamforming (ZFBF) with the proposed DEFCON scheme considerably outperforms previous limited-feedback MU-MIMO schemes such as ZFBF with conventional static feedback method and per user unitary beamforming rate control (PU²RC).