This Small Business Technology Transfer (STTR) Phase I project seeks to develop secure/covert short-range wireless personal area communication networks by addressing the critical technical challenges of RF communications in harsh environments. The key new contributions in this proposed work include advanced techniques in the following areas: RF channel equalization, multi-pulse modulation for covertness and enhanced data security at the physical layer, adaptive noise and interference cancellation, multiple-input multiple-output antennas for capacity maximization, and wideband antenna design techniques for overcoming severe signal attenuation or distortions. Success in Phase I will lead to development of a powerful and flexible Software Defined Radio solution for covert communications with exceptionally high data security and operating in harsh propagation environments for distances up to at least 100 m. Proposed techniques are virtually certain to overcome the main obstacles that have prevented previous traditional communications systems, including the ultra-wideband ones, from succeeding in an array of commercial and government applications such as first-responder communications, communications in harsh environments, and related areas.
The broader impact/commercial potential of this project is not only significant for defense and related government applications, but may also enable numerous commercial opportunities. On the government and military market fronts, there are numerous Department of Defense and intelligence community needs that can be better addressed by the novel communications system approach proposed. These include shipboard communications systems, urban rescue missions, some subset of tactical communications in harsh environments, intelligence field missions requiring stealthy communications in all environments (including urban settings), and many others. Beyond the clear national security payoffs, broader societal payoffs could include personal security, police and fire rescues, and possibly other less obvious applications involving short-range communications and personal area networks. It is expected that these advances will enable successful communications systems in many areas where traditional systems fail, and that the funding of this project will facilitate a much broader set of high-impact, dual-use applications. The proposed new communication systems embody unique features, modulation schemes, and other technical methods which will expand the understanding and applicability of these novel approaches to difficult communication environments.
Background This Small Business Technology Transfer project seeks to develop secure/covert short-range wireless personal area communication networks by addressing the critical technical challenges of RF communications in harsh environments. The key new contributions in this proposed work include advanced techniques in the following areas: RF channel equalization, multi-pulse modulation for covertness and enhanced data security at the physical layer, adaptive noise and interference cancellation, multiple-input multiple-output antennas for capacity maximization, and wideband antenna design techniques for overcoming severe signal attenuation or distortions. This project will result in commercial products including 1) secure and robust walkie-talkie communications and 2) wideband (pulse-based) commercial electronics products such as antennas and pulsers. These techniques are virtually certain to overcome the main obstacles that have prevented previous traditional communications systems, including the ultra-wideband (UWB) ones, from succeeding in an array of commercial and government applications such as first-responder communications, communications in harsh environments, and related areas. Results and Outcomes A key objective met was to develop transceiver designs that function ultra-reliably in jamming and multipath environments. Our initial goal focused on short range (< 300 m), but we also addressed how the prototype system design can be extended for much longer ranges (1000 m or more). Other design objectives met were size, weight and power: small-size (hand-held), light-weight (<2 lbs), and low-power (~100 mW) battery-operated system. The DSI walkie-talkie design lends itself to eventual low-cost production. The major contributions made include theoretical analysis and design, computer simulations, and data collection from field tests to support the following four specific technical areas: (1) RF channel equalization, real-time and wideband, to take advantage of multipath reflections for reliable communications in highly reflective electro-magnetic channels; (2) Multi-pulse delay-coded modulation for covertness and enhanced data security at the physical layer. While higher layer encryption can be incorporated onto the Dirac Solutions Inc. (DSI) radios, our approach involves physical layer encryption that would be extremely difficult to break even by determined adversaries; (3) Modified pulse repetition frequency (PRF) modulation (a proprietary new signal modulation technique) for high fidelity communications in jamming; (4) Wideband antenna design matched for wideband RF pulses to overcome antenna insertion losses such as waveform distortions and non-linear phase response. A novel Vivaldi-type antenna with ultra-wideband linear phase response and high-gain, required for MIMO UWB radios, has been invented, developed and tested. In the Phase I STTR effort, we used the pre-existing DSI UWB walkie-talkie prototypes to determine and specify the requirements for optimal channel equalization and modulation techniques in the software-defined radio design. DSI continued an ongoing extensive field testing campaign using design prototype radios in ships, mines, shafts, and urban areas. The hardware communication system tested on a navy ship was able to communicate from the engine room to the first deck with hatches closed, something traditional narrow-band walkie-talkies could not accomplish. It was realized early in the project that some of the thrusts could be important in their own right, independent of the overall project goals. Two of these include the wideband Vivaldi-type antenna invention described above, and the advanced pulser electronics for wideband pulse generation being developed in the hardware walkie-talkie. In the case of the Vivaldi-type antenna, DSI has already used non-STTR funds to develop prototypes and built several antennas for commercial sale. Similarly, in the case of the pulser DSI used non-STTR funds (IR&D) to build multiple pulser boards for use in the hardware walkie-talkie and possibly adjacent pulser electronics activities. Impacts With further development, it is likely that these new pulsed wideband communications will find some important uses in the defense, military, first responder, and possibly mining communities. Preliminary discussions are already underway with several agencies and companies working in those arenas. There are numerous potential commercial arenas where the new pulsed wideband systems being developed herein could eventually have impact. These include hospitals, the shipping industry, cruise ships, and many others. These will begin to be explored in more detail in the near future, even before the commercial prototypes that will be developed in the next year or two. Importantly, the work herein also advances the core mission of the NSF EARS (Enhancing Access to the Radio Spectrum) program in that it makes simultaneous use of broad swaths of the radio spectrum, independent of any other users occupying those parts of the spectrum.
