Analysis of linear and non-linear precoding techniques for the spatial separation of unicast and multicast users

The provision of multicast services is a relevant feature in the context of the further evolution of cellular communication systems. The scope of this paper lies on the analysis and comparison of linear and non-linear downlink precoding techniques for separating users of both unicast and multicast services in space. The paper investigates and derives a non-linear algorithm based on Tomlinson-Harashima precoding (THP) for this unicast/multicast scenario. It is seen that, differently from the linear case, the application of a non-linear multicast-aware algorithm is not capable of providing significant gains. Additionally, a hybrid linear/non-linear algorithm is proposed, which is shown to achieve a good trade-off between performance and complexity.