Channel representative interference cancellation (CRIC) for MIMO multi-hop systems in the Manhattan scenario

The particular topology found in metropolitan areas can be exploited by employing relay nodes, which turn one-hop non-line-of-sight connections into multi-hop line-of-sight ones, thereby reducing the shadowing. However, this topology should also be considered to avoid multi-user interference and thus exploit the spatial resources optimally. Nevertheless, in most approaches which deal with this scenario, the interference is either completely neglected or estimated with strong simplifications. In this paper, we analyze the interference among users in a 4-way junction on the downlink and show that it should not be ignored. Based on this observation, we propose the channel representative interference cancellation (CRIC) scheme. The interference between users in the same street is suppressed by CDMA, whereas the one between users of different streets by the successive minimum mean square error (SMMSE) precoder. Due to the dimensionality restrictions given by SMMSE, we introduce a channel representative, which, serving as a virtual user, reflects the spatial features of all users in one street.