We investigate zero-forcing and unitary precoding for multi-user MIMO in the downlink of a multi-cell network. By considering additional aspects, such as realistic link adaptation, the associated block errors and retransmissions, robustness to uncertainty in interference, and the computation of receive filters, we complement and extend existing results on the topic. To support our theoretical considerations, an excessive simulation campaign has been performed using an LTE-Advanced systemlevel simulator and the key results are presented in this paper. Our conclusion is that unitary precoding may be competitive to zero-forcing in some scenarios, while being less complex and having less overhead. The presented simulation results are reproducible and extendable because the complete source code is provided online under a GPL license.
['Jan Ellenbeck', 'Andreas Dotzler', 'Wolfgang Utschick']
Interference robustness for MIMO networks — System-level performance evaluation for LTE-Advanced