KEYWORDS: Communications, distributed beamforming, cooperative beamforming, collaborative beamforming, synchronization, radiation pattern, near-field, far-field, space-time, electronic warfare, interference mitigation.

OBJECTIVE: To facilitate the adoption of resilient communications within the Army by developing the capability to apply distributed beamforming techniques to non-developmental waveforms for cost effective communication systems with greater range and power-efficiency and lower detectability then current communications technologies. ITAR: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

DESCRIPTION: The US Army C5ISR Center is interested in the development of technology to enable the application of distributed beamforming communications techniques to non-developmental waveforms. Distributed beamforming techniques have matured significantly over the past decade, but currently rely on unique waveforms often with costly computational and hardware requirements. The ability to apply distributed beamforming techniques to non-developmental waveforms can greatly facilitate integration of the technology into tactical communications architectures. Distributed beamforming using dismounted soldier radios can emulate an antenna array and obtain power and/or directivity gains which are proportional to the number of dismounted radios, and be used to deliver a common message to a mounted receiver or possibly another collection of dismounted soldiers. Benefits of distributed beamforming include energy efficiency, improved communication range (or an equivalent lowering in detection range with respect to an adversary), interference rejection, and possibly the ability to spatially multiplex streams of data if desired. The C5ISR Center particularly seeks techniques, which can be used for squad level communications. The Army squad must be able to communicate with a separated parent vehicle in poor visibility or over restrictive terrain in a manner which reduces vulnerability to enemy interception/detection (LPI/LPD) and enhances Anti-Jam (AJ) capabilities in congested/contested environments. The US Army SBIR office and C5ISR Center are requesting information related to distributed beamforming methods designed for dismounted soldiers where each soldier has a radio and omnidirectional antenna, and where each soldier acts as a node in the distributed dismounted beamforming system. The dismounted soldiers must be able to communicate, in a cooperative manner, with a radio mounted on a vehicle, where the mounted radio may use multiple antennas. The capability must demonstrate AJ/LPI/LPD characteristics while operating in a congested/contested environment. Waveforms in consideration for this effort should be non-developmental in nature. The ability to update existing tactical radios with this capability via software/firmware update is highly desirable. The approach should maximize portability and backwards compatibility to tactical radio systems which will support widespread implementation and reduce overall cost. Consideration will be given to government owned and government purpose waveforms. The Joint Tactical Networking Center (JTNC) DoD Information Repository and JTNC Tactical Communications Marketplace, both available at https://www.public.navy.mil/jtnc/Pages/home.aspx, are resources to gain access to these waveforms.

The proposal should contain information regarding the beamforming (or diversity) implementation, and specifically how LPI and LPD are improved by the beamforming methods. Furthermore, the proposal should contain any information regarding the characteristics of the beamforming methods that facilitate improved resistance to intentional and non-intentional interference, both from enemy and friendly forces in congested/contested environments. Typical concepts of operation would include forward dismounted reach-back to a vehicular platform that may or may not be under condition of enemy electronic warfare (EW) attack (electronic support (ES) and electronic attack (EA)), support for route clearing operations that might use a Counter Remote Controlled Improvised Explosive EW (CREW) device to block enemy communications, and tactical dismounted operations in dense urban terrain typical of building search and clearing, which are assumed to be highly congested/contested environments. The system must provide up-echelon communications to at least 5000m to a reach back node that is mounted or dismounted. The solution must also provide communications, AJ, LPI, and LPD capabilities when the reach-back distance is lower than 5000m. Frequency Bands of interest are VHF, UHF, L-Band, and S-Band. Real time voice, push-to-talk (PTT), and data demonstration is expected as a part of this effort. Open standard and non-proprietary interfaces shall be available for connection of audio and data connection ports. Data rates will be available to support transfer of voice and position location information. Solutions which provide additional data rates which support file transfer and streaming video services are also of interest.

Phase 1: The Phase I effort shall include a feasibility study of the incorporation of distributed beamforming methods to non-developmental waveforms to include frequency offset and time/phase synchronization as well as the impacts of other waveform aspects such as modulation and coding. Additionally an overall consideration of system architecture feasibility incorporating the various individual blocks (modulation, synchronization, demodulation, etc.) should be included. An analysis of the theoretical limits of the various technical approaches shall be presented in addition to any practical limitations for the approaches. Analysis should be reinforced with simulation of the approaches. The Phase I effort will identify the optimal approach and provide a recommendation for Phase II implementation. The Phase I deliverable will be a report documenting the results of the feasibility study and simulation software with short exemplary use-cases for the simulation software allowing reproduction of some key simulation results from the report.

Phase 2: The Phase II effort shall implement and demonstrate the operation of a TRL 5/6 prototype distributed beamforming system using a non-developmental waveform(s). The prototype systems shall incorporate the techniques researched in Phase I. The prototype shall be delivered to the government with an associated user manual and a report documenting the results of the Phase II effort. The system is expected to be evaluated and demonstrated at the Command, Control, Communications, Computers, Cyber, Intelligence, Surveillance, and Reconnaissance (C5ISR) Center Ground Activity in Ft. Dix, NJ. The demonstration shall include full beamforming with a minimum of 4-nodes. The system architecture should be scalable and support team sizes of at least 11-nodes. It is further desirable to support squad-to-squad beamforming without a dedicated base station. The Army is interested in performance in unobstructed line of sight (LOS), restricted, and urban terrains under benign and contested electromagnetic environments. The Phase II effort shall include an operationally relevant field demonstration of the prototype systems, which demonstrates at least real-time transfer of voice/PTT and position location information (PLI) data. Demonstration of higher throughput applications is desirable. The test environment shall be a GFE provided test facility.

Phase 3: Phase III efforts will focus on reducing the size, weight, and power of the Phase II prototype, maturing the prototypes to TRL 6/7 for integrating into the appropriate Army Program of Record. The technology developed under Phase II may also be modified and transitioned to the commercial cellular industry for appropriate use in 5G (or other) systems. The capability proposed in this SBIR is beneficial to commercial uses for first responders in disaster relief communications where critical communications infrastructures are unavailable. Distributed beamforming of small teams increases the reach-back communications distances; especially in challenging environments with path obstructions such as buildings or foliage.

AVAILABLE DOCUMENTS/REFERENCES:

Mudumbai, R., Brown D. R., Madhow, U., Poor, H. V., Distributed Transmit Beamforming: Challenges and Recent Progress, IEEE Communications Magazine, pp. 102-110, February 2009; Barriac, G., Mudumbai, R., Madhow, U., "Distributed Beamforming for Information Transfer in Sensor Networks," Third International Symposium on Information Processing in Sensor Networks (IPSN), 2004.; Ochiai, H., Mitran, P., Poor, H.V. and Tarokh, V., "Collaborative Beamforming for Distributed Wireless Ad Hoc Sensor Networks," IEEE Transactions on Signal Processing, Vol. 53, No. 11, pp. 4110-4124, November 2005.; Mudumbai, R., Barriac, G., and Madhow, U., " On the Feasibility of Distributed Beamforming in Wireless Networks," IEEE Transactions on wireless Communications, Vol. 6, No. 5, pp. 1754-1763, May 2007.; Thibault, I., Faridi, A., Corazza, G.E., Vanelli Coralli, A., and Lozano, A., "Design and Analysis of Deterministic Distributed Beamforming Algorithms in the Presence of Noise," IEEE Transactions on Communications, Vol. 61, No. 4, pp. 1595-1607, April 2013