Resource allocation is a major research field in wireless networks. The main challenge is to find the most suitable user for each time and frequency resource to reach the quality of service requirements. The necessity to always increase the capacity of wireless networks leads to systems using more and more antennas. Namely, the use of Massive-MIMO (Multiple Input Multiple Output) allows to simultaneously schedule several users on the same frequency resource. This is a new paradigm for resource scheduling. In this context, resource allocation algorithms have to include in their decision mechanism the choice of users association on the same time and frequency resource. A possible strategy, seen in the state of the art, is to base this user grouping on their channel-matrix correlation to minimize the interference level. In this paper we show the limited use of this approach in a system using block diagonal precoder.