Exploitation of MIMO techniques for reliable HF communication

HF Communication has been synonymous with long ranges achievable using relatively inexpensive equipment. The downside though, has been the highly unreliable nature of the HF Ionospheric channel, which has deterred the development of systems capable of exploiting the large ranges achievable using sky wave/ionospheric propagation. The ionospheric channel is characterized by extensive multipath fading which is a substantial impediment for HF communication systems. MIMO (Multi Input Multi Output) systems on the other hand, exploit multipath to substantially improve communication efficacy and have been successfully employed in Wi-fi, cellular and VHF range applications. This paper studies the feasibility of exploiting MIMO techniques to exploit the Multipath effects prevalent in HF Ionospheric channel so as to improve the BER efficiency of data communication over HF links. Simulations for HF communication system using multiple transmit and/or receive antennas show substantial improvement in performance (E_b/N_o v/s BER) vis-à-vis the case of single transmitter and receiver. It is shown that diversity gain achieved compares to the maximum gain possible as in the case of MIMO over VHF and Wi-Fi applications.