Frequency correlation of an indoor MIMO channel

This paper describes the indoor measurements of a dual multiple-input multiple-output (MIMO) system, conducted at the 2.5 GHz band. We are mainly interested in the double-directional channel response of each frequency band and especially in the degree of similarity between them. In principle, when a frequency division duplex (FDD) system is deployed (like in UMTS) it is really challenging to study whether the measurement results of the uplink could be mapped to the downlink direction (and vice versa). In our study two different beamformers as well as the multiple signal classification (MUSIC) algorithm are included in order to assess the angular domain performance of both bands. The initial results reveal that joint spectra exhibit a noticeable degree of similarity implying that the two bands are characterised by the same propagation mechanisms. Evidently, the crucial issue is to investigate whether these measurement results could be exploited in future practical FDD systems.