Category Archives: Publications

A New MIMO HF Data Link: Designing for High Data Rates and Backwards Compatibility

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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.

HF MIMO NVIS Measurements with Colocated Dipoles for Future Tactical Communications

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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.

60 GHz Wireless Communications: Emerging Requirements and Design Recommendations

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Abstract: Multiple GHz of internationally available, unlicensed spectrum surrounding the 60 GHz carrier frequency has the ability to accommodate high-throughput wireless communications. While the size and availability of this free spectrum make it very attractive for wireless applications, 60 GHz implementations must overcome many challenges. For example, the high attenuation and directional nature of the 60 GHz wireless channel as well as limited gain amplifiers and excessive phase noise in 60 GHz transceivers are explicit implementation difficulties. The challenges associated with this channel motivate commercial deployment of short-range wireless local area networks, wireless personal area networks, and vehicular networks. In this paper we detail design tradeoffs for algorithms in the 60 GHz physical layer including modulation, equalization, and space-time processing. The discussion is enhanced by considering the limitations in circuit design, characteristics of the effective wireless channel (including antennas), and performance requirements to support current and next generation 60 GHz wireless communication applications.

by Kuma CTO Robert Daniels and CINO Robert Heath, Jr.
Copyright 2007 IEEE. Reprinted from IEEE Vehicular Technology Mag., v. 2, no. 3, pp. 41-50, Sep. 2007.

60 GHz Wireless: Up Close and Personal

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Introduction: The millimeter-wave band, especially the unlicensed spectrum at the 60 GHz carrier frequency, is at the spectral frontier of high-bandwidth commercial wireless communication systems. Compared with microwave band communication, spectrum at 60 GHz is plentiful (frequencies of 57–64 GHz are available in North America and Korea, 59–66 GHz in Europe and Japan [1], [2]), but attenuation is more severe (20 dB larger free space path loss due to the order of magnitude increase in carrier frequency, 5–30 dB/km due to atmospheric conditions [3], and higher loss in common building materials [4]). These characteristics make 60 GHz communication most suitable for close-range applications of gigabit wireless data transfer.

by Kuma CTO Robert Daniels, CINO Robert Heath, Jr., et al.
Copyright 2010 IEEE. Reprinted from IEEE Microwave Mag., pp. S44-S50, Dec. 2010.