Beamforming with relays in multicell networks based on correlation knowledge

In a multicell network with a frequency reuse-1, intercell interference (ICI) is a limiting factor. Especially cell edge users are subject to strong ICI. With beamforming the signal to interference plus noise ratio (SINR) of the cell edge users can be improved. Beside the interference of adjacent cells, cell edge users are often shadowed. In order to overcome this problem, relays in the cell edge region are additionally used. In long-term evolution, two types of relays are proposed. The first one, called type-1 relay and owns a cell, the second one is called type-2 relay and only supports the base station. This paper considers the type-1 relay only and proposes a joint max-min beamforming and scheduling algorithm to maximize the SINR of cell edge users. In multicell networks, the optimization based on instantaneous channel state information (CSI) becomes infeasible, therefore, long-term CSI in form of spatial correlation matrices are used for the optimization. Numerical results underline the performance gain compared to conventional networks without relays.