HF MIMO NVIS Measurements with Co-located Dipoles for Future Tactical Communications

Multiple antennas in transceivers can increase system spectral efficiency, reduce transmit power, enable robustness to interference, and increase overall reliability through multiple-input multiple-output processing (MIMO). Consequently, high frequency (HF) networks, which feature extreme spectrum scarcity and unreliability, are prime for MIMO exploitation. Unfortunately, the desired antenna spacing for MIMO is proportional to the wavelength (tens of meters at HF). One promising approach is to utilize two antennas in a single antenna footprint through cross-polarization. This configuration has not yet been fully validated for MIMO at HF. In this paper, we demonstrate MIMO capabilities in near vertical incidence sky-wave (NVIS) propagation through a measurement campaign. This paper shows that MIMO is a game changer for HF NVIS with up to 2.27x data rate gains, up to 9x less transmit power, and > 3x fewer link failures. This paper also provides critical channel metrics for baseband designers of future MIMO HF protocols as demonstrated in our companion paper [1].