Monthly Archives: August 2013

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Abstract: High frequency (HF) radios (the 3-30 MHz range) are useful for tactical communications because of their ability to communicate over long distances or around large obstructions without supporting infrastructure and in satellite-denied environments. Bandwidth is very scarce in the relatively low carrier frequencies of HF systems, increasing the importance of high spectral efficiency communications. The use of multiple antennas, along with intelligent signal processing, known as multiple-input multiple-output (MIMO), has been applied to commercial wireless systems. MIMO dramatically increases spectral efficiency, reduces transmit power, enables robustness to interference, and increases overall reliability. In a companion paper, we have proven the feasibility of HF MIMO using compact cross-polarized arrays through measurements. In this paper, we leverage those measurements to motivate a MIMO HF physical layer based on the existing single-antenna MIL-STD-188-110C Appendix D standard. Simulation results that also exploit these measurements show a 116% improvement in overall throughput and a 15 dB signal-to-noise ratio (SNR) improvement for the highest-rate modes due to greater reliability and reduced sensitivity to amplifier nonlinearities.

by Kuma CTO Robert Daniels and CEO Steven Peters
Copyright 2013 IEEE. To appear in IEEE MILCOM 2013 Proceedings, Nov. 2013.

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Abstract: 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 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 2.27x 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.

by Kuma CTO Robert Daniels, CEO Steven Peters, and CINO Robert Heath, Jr.
Copyright 2013 IEEE. To appear in IEEE MILCOM 2013 Proceedings, Nov. 2013.