A reduced complexity MIMO broadcast scheme: Away between opportunistic and dirty paper implementation

Departing from the opportunistic schemes in Multiuser Broadcast MIMO schedulers, practical transmission techniques to get closer to the channel capacity are proposed for the outdoor urban scenario. By considering the Spatial Power Density function of the arriving signal, the paper develops different setups based on the quantity of available Channel State Information at the Transmitter side (CSIT). In a first approach, Signal to Noise Interference Ratio (SNIR) feedback scenario is considered, but to further decrease the gap between the channel capacity and the proposed scheme, the system can ask for full CSIT to the progressively scheduled users in order to improve the opportunistic user selection, while at the same time, an interference cancellation to the previously scheduled users is accomplished. The proposed schemes are compared via simulations with other possible transmission strategies in terms of system sum rate.