Retrodirective Coherency Linking Advanced Squads to Squads (ReCLASS) Phase 2

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).