Investigation of signal correlation for spaced and co-located antennas on multipath hf links and implications for the design of SIMO and MIMO systems

MIMO (Multiple Output Multiple Input) systems employ both transmitting and receiving arrays and space-time coding methods in order to achieve significantly greater channel capacities. Since the data rate possible for digital HF systems is generally comparatively low, it would be very useful if the capacity improvements inherent in MIMO techniques could be exploited at HF. In order to assess this possibility and in order to gain some insight into the optimum design of HF MIMO systems, the characteristics of the digital HF channel are explored in relation to this utilization. To accomplish this a wideband HF simulator, based on a physical model and including time-varying electron density irregularities is employed and used to assess correlation of the received multi-component signal at spaced antennas for different multipath scenarios and ionosphere parameters. The optimum parameters and scenarios for employment of HF MIMO systems are then discussed.