In state-of-the-art multiuser multicell communication systems, bandwidth is a limited resource and reused in adjacent cells. A high spectral efficiency is achieved by a network-wide configuration with frequency reuse-one. In these reuse-one networks (RONs), intercell interference (ICI) emerges in the case of a unicast transmission as a critical limiting factor.
An important optimization criterion in network design is a fair distribution of the throughput among the users while maximizing the sum rate of the total network. This is a particular issue in RONs. A network-wide maximization of the signal to interference and noise ratio (SINR), which corresponds to the mitigation of intercell interference, can be achieved by the optimal assignment of the resources in the time-, frequency- and spatial domain.
This project uses beamforming to exploit the spatial domain and temporal user scheduling to exploit the temporal domain. Many previous works on ICI mitigation are based on instantaneous channel state information (CSI). In a coordinated multicell scenario, these strategies become extremely difficult to implement due to the increasing computational complexity and communication overhead for acquiring short-term CSI. The motivation of this project is to optimize the beamforming and the scheduling decisions by exploiting long-term CSI in terms of downlink spatial covariance matrices. Then the optimization of the beamforming weights and scheduling decisions can be done offline by a central unit and reused as long as the long-term CSI is valid. A reduced signaling overhead is the consequence, which is important criterion in a multicell scenario.
We consider two approaches for interference mitigation with long-term beamforming: