Capacity Measurements in a Multicell MIMO System

In future wireless networks, cooperation between the base stations may reduce the effects of intercell interference and enhance the capacity per cell. In this paper, the potential of such cooperation is evaluated using measurements of the informationtheoretic channel capacity at 5.2 GHz in 4 overlapping urban microcells with 5 users. In each link, a 10-transmit 16-receive antenna configuration is used. Results for individual links between terminals and base stations indicate that, in 60% of the scenarios, the direct signal has a significant impact. It contributes two spatial degrees of freedom due to the polarization which is confirmed by ray tracing. Rich scattering is observed when the direct signal is blocked. Measurements in the multicell scenario demonstrate that the intercell interference leads to an enhanced rank of the joint multiuser multicell channel matrix. Compared to a conventional cellular system, where different radio resources are assigned in adjacent cells in order to avoid the interference, it is better to exploit the interference by cooperation which results in a five times higher spectral efficiency.