Nuclear quadrupole resonance (NQR) is a radio frequency (RF) magnetic spectroscopic
technique that has been shown to detect and identify a wide range of explosive materials
containing quadrupolar nuclei. The NQR response signal provides a unique signature of the
material of interest. The signal is, however, very weak and can be masked by non-stationary RF
interference (RFI) and thermal noise, limiting detection distance. In this paper, we investigate the
bounds on the NQR detection range for ammonium nitrate. We leverage a low-cost RFI data
acquisition system composed of inexpensive B-field sensing and commercial-off-the-shelf
(COTS) software-defined radios (SDR). Using collected data as RFI reference signals, we apply
adaptive filtering algorithms to mitigate RFI and enable NQR detection techniques to approach
theoretical range bounds in tactical environments.
The implementation of network centric warfare on the battlefield has driven the growing demand for high capacity warfighter communication systems. Although new high capacity SATCOM systems such as WGS are being introduced in the near term, these systems use the interference avoidance paradigm, which fundamentally limits overall network performance. This paper introduces a new wireless networking paradigm called Interference Multiple Access (IMA), developed under the auspices of DARPA. The interference multiple access paradigm exploits multi-access interference to enable revolutionary improvements in wireless communication capacity and latency without the need for infrastructure, coordination, or spectrum preplanning. Simulation and over-the-air test results suggest that greater than 3X increases in network throughput (especially in low SNR scenarios) can be achieved over traditional contention and scheduled-based spectrum access approaches when applied to WIN-T NCW terminals communicating in a mesh topology over the WGS constellation.
The advent of network coding promises to change many aspects of networking. Network coding moves away from the classical approach of networking, which treats networks as akin to physical transportation systems. We overview some of the main features of network coding that are most relevant to wireless networks. In particular, we discuss the fact that random distributed network coding is asymptotically optimal for wireless networks with and without packet erasures. These results are extremely general and allow packet loss correlation, such as may occur in fading wireless channels. The coded network lends itself, for multicast connections, to a cost optimization which not only outperforms traditional routing tree-based approaches, but also lends itself to a distributed implementation and to a dynamic implementation when changing conditions, such as mobility, arise. We illustrate the performance of such optimization methods for energy efficiency in wireless networks and propose some new directions for research in the area.
Current military operational effectiveness can degrade rapidly with increasing communications stresses such as heavy throughput and QoS demands from disadvantaged users exposed to severe channel impairments and communications threats. This paper proposes a distributed and agile radio resource management (RRM) system to maintain mission effectiveness even under significant communications stress. Agile RRM includes a well-coordinated cross-layer design with the introduction of new OSI layer features and interactions as well as methods to incorporate communications constraints and requirements in systems controlling mission planning and execution.