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Dynamic Digital Spatial Nulling Algorithms for Tactical Data Links


TECHNOLOGY AREA(S): Air Platform, Electronics, Battlespace 

OBJECTIVE: Develop and/or innovate new or current algorithms including derivatives of space-time adaptive processing (STAP), space-frequency adaptive processing (SFAP), and key elements for nulling-aware routing for application on tactical data links to improve the communication range, interconnectivity and anti-jamming resistance. Document, assess, rank, recommend and report any algorithms based on applicability, performance and integration complexity to military communications and data terminals. Pursue feasible candidate(s) for a potential transition into Multifunctional Information Distribution System Joint Tactical Radio System (MIDS JTRS) terminals during Phase II prototyping efforts. 

DESCRIPTION: Adaptive null steering was pioneered in the early 1960’s [Refs 1, 2, 3, 4] in the context of side-lobe cancelation (SLC) for the purpose of suppressing radar receiver interference and jamming. The ability to control the phase and amplitude of received signals on each channel of an antenna array makes it possible to implement various types of adaptive analog or digital processing techniques. This capability has been extensively used in analog, digital and hybrid analog/digital antenna systems to suppress jammer signals in radar and communications systems. Extension of these techniques to multi-element antennas to cancel multiple interference sources has occurred. Many modern and legacy communications links have relied on dual antenna solutions for antenna diversity to improve the quality and reliability of a wireless link, but only a few protocols leverage null-steering due to platform constraints. Most platforms, mobile and non-mobile, rely on single or dual antenna systems for transmission and reception capability, placed in a number of different geometries. Adversarial nodes with 3D moment capacity pose a significant threat to these networks as an adversary can position itself to attack the crucial links [Ref 4]. Mobility of platforms and interferences sources make nulling decisions difficult as the null could be placed such that signals of interest are also affected. The Navy needs innovative adaptive and deterministic steering algorithms to process dual digitized inputs, based on two separated antennas implemented in a Field Programmable Gated Array (FPGA) to improve by 30 – 60 dB, communications resilience in a contested environment. Additional antennas may be supported, but two will be assessed for optimality. Algorithms should also be able to accept and provide angle of interests of multiple interfering signals to allow for high-order media access control and routing protocol utilization for optimally steering gain. Analysis and simulations that allow for comparison of performance on proposed new algorithm and/or innovated application of current algorithms and estimates of the computational requirements should accompany the research. The interference removal should not degrade the link compared to a non-null steering setup. Algorithm parameters should be developed and identified that will be used for a future link layer algorithm that allows for cooperative nulling, allowing trades to be made between nulling adversarial and friendly nodes to preserve interconnectivity and data dissemination capability. Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by DoD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Security Service (DSS). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DSS and NAVAIR in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advanced phases of this contract. Although not required, it is highly recommended to work in coordination with the original equipment manufacturer (OEM) to ensure proper design and to facilitate transition of the final technology. 

PHASE I: Develop, design, and demonstrate the feasibility of new or existing innovative dual antenna processing techniques for tactical data links and establish the base figure of merit: geometries supported, null depth, ability to adapt to prevent friendly nulling. As part of the Phase I effort, simulations are required to establish the Figure of Merit (FOM) for the proposed algorithms by both the Offeror and the Government. FOMs allow for both offeror and government to have a single standard unbiased test methodology to validate algorithms FOMs, as each algorithm offer different performance for different interference sources. In the Phase I, the offeror will assume multiple interferences sources exist. MIDS JTRS is a NSA certified type 1 encryption system; hence, information assurance (IA) compliance will apply during the Phase II and subsequent transition efforts. The Phase I effort will include prototype plans to be developed under Phase II. 

PHASE II: Produce, deliver, and implement (in software) prototypes for the proposed algorithms, encompassing both the design of the algorithms and anticipated affects. Conduct evaluations by testing the algorithms against signal sets. MIDS JTRS is a NSA certified type 1 encryption system; hence, information assurance (IA) compliance will apply during the Phase II and subsequent transition efforts. The Government, at its discretion, may also provide threat signal data for testing. Independent testing at a Government facility at Government expense may be performed. Performance of the algorithms will be judged based on the base figure of merits assumed above. Prepare a Phase III development plan to transition the technology for Navy and potential commercial use. Work in Phase II may become classified. Please see note in Description section. 

PHASE III: Support the Navy in transitioning the algorithms to Navy use. Refine further the algorithms, software code, validation, documentation, and IA compliance. Perform test and validation to certify and qualify software and firmware components for Navy use. Implement the capability in the form of fast, efficient algorithms that, once proven, can be coded in software-defined radios. Spatial nulling algorithms have increasing application in the area of dense enterprise wireless local area networks and commercial antenna systems and cellular communication. Spatial nulling technology potentially has wide commercial applications to address LTE, 5G, WIFI technology deployment due proximity with other interferes, spectrum challenges, etc. 


1. Howells, P. W. Intermediate Frequency Side-Lobe Canceller. Morrisville: United States Patent Office, 1965.

KEYWORDS: Data Links; Software Defined Radios; Space-Time Adaptive Processing (STAP); Space-Frequency Adaptive Processing (SFAP); Digital Nulling; Figure Of Merits (FOM) 

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