Experimental investigation of a joint dual-spaced diversity and tri-polarised MIMO system for beyond 3G

In this paper, we present the results of an investigation into the performance of an antenna architecture that simultaneously utilises the spatial and polarization dimensions to offer diversity and provide three orthogonal and independent subchannels respectively. Experimental results indicate that such a system would provide a 10% outage capacity gain of 8.5 b/s/Hz or 42.5 Mb/s in a 5 MHz UMTS channel over the traditional single-input single-output (SISO) system. At the same time, an equal gain combining (EGC) diversity gain of up to 6 dB is obtained. It is demonstrated that correlation values in both the spatial and polarization dimensions are substantially low, i.e. below the threshold of 0.7. We also illustrate how the combined gain is reduced when the mode of operation is changed so that diversity is implemented in the spatial dimension and MIMO in the polarisation dimension. This system can adaptively operate in three modes, including a 6×6 MIMO operational mode in situations that do not need any diversity but offer a very high-data rate. Since the polarized antenna elements are co-located, the resulting compact system would be a good candidate for beyond 3G designs of robust high-performance small handsets.