Evolution of Downlink Multi-Antenna Techniques throughout E-UTRAN LTE Releases

In this paper we present the evolution of downlink multi-antenna techniques over different releases of E-UTRAN LTE specifications. First we walk through the design of MIMO transmission schemes, reference signals and channel state information feedback from Release 8 to the latest Release 10 of the specifications. We provide extensive system simulation results for downlink single- and multi-user MIMO, demonstrating the clear performance benefits of the advanced spatial processing techniques developed throughout the evolution of LTE, and confirming the state-of-the-art design of LTE multi-antenna techniques. Finally, we provide a glimpse to the future multi-antenna topics currently being studied in 3GPP, presenting also simulation results on the most promising candidate feature.