S. W. Peters, R. C. Daniels, and Robert W. Heath, Jr.
Submitted to the Proc. of MILCOM, November 18 - 20, 2013.
Multiple antennas in transceivers can increase system spectral efficiency, reduce transmit power, enable robustness to interference, and increase overall reliability through multipleinput multiple-output processing (MIMO). Consequently, high frequency (HF) networks, which feature extreme spectrum scarcity and unreliability, are prime for MIMO exploitation. Unfortunately, the ideal 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. Cross-polarized antennas, however, have not yet been proven feasible for MIMO at HF. In this paper, we demonstrate this feasibility through a measurement campaign with near vertical incidence skywave (NVIS) propagation. This paper shows that MIMO is a game changer for HF NVIS with up to 2:27 data rate gains, up to 9 less transmit power, and greater than 3 fewer link failures. This paper also provides critical channel metrics for baseband designers of future MIMO HF protocols.