Measured MIMO Capacity Enhancement in Correlated LOS Indoor Channels VIA Optimized Antenna Setups

Our premise in this paper is to investigate the available channel capacity of MIMO systems in correlated transmission channels for various antenna arrangements differing in their suitability in order to construct high rank LOS channels. Hence, a measurement campaign with a fast 5×5 MIMO channelsounder was carried out in a typical, medium scale, in room office scenario giving the opportunity to virtually evaluate the channel capacities for arbitraryM × N MIMO systems ({M,N} ≤ 5) by antenna selection and combination. We use linear antenna arrays and vary their initial antenna spacings and orientations relative to each other which coincides with LOS channels of varying rank. In the sequel the measured capacities are compared giving an idea on the usefulness of the high rank LOS channel construction in the presence of strong reflections. For our purpose we introduce an appropriate power normalization of the channel transfer matrix to exclude further effects on the capacity, as for example SNR variations due to varying transmitter receiver distances, and only concentrate on the phase angle relations within the matrix. The results show a measurable benefit in channel capacity when such optimization and normalization is performed, especially for small antenna numbers.