Multi-User MIMO Communications

In cellular networks, where a base station needs to transfer data to and from several users, it is possible to exploit the spatial degrees of freedom offered by several antennas at the base station to serve multiple users simultaneously.

This kind of transmit strategy, referred to as multi-user MIMO, potentially leads to significant gains in throughput since several data streams are transmitted simultaneously. This gain is called multiplexing gain and does also appear in point-to-point MIMO settings.

We work on multi-user MIMO in the context of massive MIMO, i.e., setups where the base station has a large number of antennas and serves a high number of users to fully exploit the multiplexing gains. In these large system settings a lot of challenges need to be solved, e.g., reducing the computational complexity, acquiring channel state information etc. Additionally, multi-user MIMO plays a role in our research on device-to-device communications. Here, the challenges focus on interference coordination between the classical cellular multi-user MIMO communications and the additional communication links directly between the mobile users.