SBIR-STTR Award

The US Army has demonstrated great support of developing robust communications in a contested and congested electromagnetic environment. Communication is often key to mission success and with growing amounts of co-channel interference and adversaries developing advanced threats aimed at detecting, geolocating, and jamming US assets, it is of the utmost importance that US troops are equipped with communication technology that can operate in these increasingly difficult conditions. Distributed beamforming is a technique that allows a wireless network of distributed transceivers to adjust their signal transmissions such that their signals coherently combine at a desired recipient’s antenna(s). The combined signal improves signal-to-interference-plus-noise ratio (SINR) at the intended recipient and reduces the residual signal in the environment that can be observed by adversarial sensors. As a result of the increased SNR at the intended recipient, the distributed transmit network can either extend their communication range or reduce the transmit power on individual transceivers to continue operating at a fixed range and lower their probability of detection and interception. Distributed beamforming techniques can also be used by the recipient to provide anti-jam capabilities. We are proposing two tasks that would help develop these distributed communication capabilities in a contested and congested environment. First, we would complete a feasibility study using the C5ISR tool TacticalComm. If successful, these simulations would allow us to develop a waveform and protocol capable of robust distributed communication in C5ISR’s desired scenarios. The simulations would address key challenges such as channel estimation with short coherence time, power control, time and frequency synchronization, data distribution, interference suppression, and scalability, and we would examine several performance metrics such as BER, detectability, and interference suppression over various parameter sweeps using TacticalComm’s batch mode. Second, we would build a software-defined radio testbed that would allow us to examine channel reciprocity with real radios. This testbed would also be the foundation for a future prototype system that would allow us to test and demonstrate the protocol we develop over the air in realistic scenarios.

The U.S. Army and other U.S. military agencies have made significant investments developing and demonstrating the use of distributed coherent beamforming techniques for tactical communications systems. Distributed beamforming provides scalability to communications, allowing a network of small size, weight, power, and cost (SWaP-C) transceivers to cooperate their RF emissions and reception to enable enhanced communications range, data rate, and/or robustness without the need for large amplifiers or large directional antennas. Army Modernization Priorities also stress the need to support communications in contested and congested environments. The directionality of distributed beamforming creates an inherently low probability of detect (LPD) and intercept (LPI) link which is difficult to localize using traditional multilateration or direction-finding approaches. It also enables the nulling of interference, which improves the resilience of wireless communications. In Phase I of this effort, Synoptic Engineering and MIT Lincoln Laboratory demonstrated a distributed network of radios can communicate to another distributed network by transmitting a common signal that’s been individually precompensated for the propagation channel between the transmitting radio and the destination. This technique, known as retrodirective or reciprocity-based beamforming, creates coherent gain that allows communication ranges and LPD/LPI benefits to scale up with the number of transmitting and receiving radios. It also provides these benefits without the use of advantaged nodes. For Phase II, we propose further development of these reciprocity-based distributed beamforming techniques to advance the state-of-the-art in this domain. The focus of this effort would be to build a prototype system that employs these techniques and is capable of reliable, scalable, fully distributed (distributed-to-distributed) coherent communications over non-line-of-sight terrestrial links. With this goal in mind, and the desire to eventually field a real-time system that can operate in contested and congested environments, we have identified four major technical objectives for this Phase II work: Demonstrate a complete, scalable implementation of reciprocity-based transmit and receive beamforming using off-the-shelf, low SWaP-C radio hardware. Investigate and implement concepts for adaptively optimizing beamforming decisions to improve communication range and/or LPD/LPI capabilities in fully distributed, over-the-air experiments. Investigate practical methods for performing space-time adaptive processing in a distributed fashion to provide real-time, anti-jam capabilities in future implementations. Explore technology transfer avenues, including accelerated ways to show interoperability with existing tactical radios and waveforms. The above work would lay the foundation for future Phase III productization of the system that could be demonstrated at TRL 6 by partnering with DOD vendor(s).