An Experimental Investigation into the Feasibility of MIMO Techniques within the HF Band

To date, MIMO research has concentrated primarily on communications within the UHF band (and above). Environments such as those associated with indoor wireless systems are ideal for the implementation of MIMO systems because of the rich multipath environment. Moreover, the small wavelengths involved permit the use of physically small antenna arrays. So far, however, very little experimental research has been conducted in the area of exploiting MIMO techniques within the HF band. Some limited modelling work in this area has been reported. The authors have recently embarked on an experimental investigation into the applicability of MIMO techniques within the HF band. State of the art digital techniques will be employed in radio links established within the UK, between the UK and France, and over a more northerly path to estimate the MIMO channel capacity from measurements. The investigation will include consideration of operational frequencies (including the effect of different mode content), antenna configurations (e.g. spaced arrays and heterogeneous co-located arrays), and geographical effects (e.g. the different nature of the ionosphere between the mid and high latitudes). A theoretical background to HF-MIMO and introductory aspects to the specific project have been presented in this paper, in addition to a preliminary analysis using data from a previous (unrelated) study.