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

Abstract

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 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 2.27× data rate gains, up to 9× less transmit power, and > 3× 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].

SC-FDE Layer for Sensor Networks in Remote Areas Using NVIS Communications

“…Despite that, not all of the HF band can be used in a NVIS link [7] and the frequencies at which radio signals refract are between 3 MHz and 10 MHz [7]. Currently, NVIS nodes can be implemented on SDR platforms [8,9] and can achieve bit rates of up to thousands of bps (if higher data rates were needed, multiple antennas could be used to take advantage of the multipath effect or with multiple antennas using different channels [10,11]).…”