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Tools are necessary for the DoD to analyze their information system's security, reliability, and resilience against cyber attack. Today's security analysis utilize real systems such as computers, network routers and other network equipment, computer emulations (e.g., virtual machines) and simulation models separately to analyze interplay between threats and safeguards. In contrast, we are developing...
Physical-layer network coding is a high-throughput technique for communicating over the two-way relay channel, which consists of two terminals that communicate exclusively via an intermediate relay. An exchange of messages begins with both terminals transmitting binary data sequences simultaneously to the relay. The relay determines the modulo-2 sum of the sequences, which it modulates and broadcasts...
Shadow zone and delay aware routing (SZODAR) scheme is a practical and distributed routing protocol that can find routes around shadow zones. In SZODAR, sensor nodes can raise or lower their acoustic transducers to a depth such that shadow zones of the neighboring nodes are avoided. The engineering parameters in SZODAR and their evaluations are also presented.
Reed Solomon (RS) forward error correction (FEC) coding in conjunction with M-ary hyper phase-shift keying (MHPSK) and soft decision decoding is considered in order to improve the robustness of a high spectral efficiency, non-linear satellite communications link. In this paper, a system that utilizes RS encoding of the information symbols which are then transmitted with MHPSK is evaluated in terms...
In this paper, we will propose a framework for computing detection (Pd) and false alarm (Pfa) probabilities for chip-time differential transmitted-reference (Tc-DTR) receivers over frequency-selective multipath fading channels further impaired by narrow-band interference (NBI). We will show that, when compared to similar non-coherent receiver architectures, Tc-DTR offers an intrinsic robustness to...
Applications operating over airborne networks are known to perform quite sub-optimally. Transmission control protocol (TCP) based applications often experience very low data throughput, while the user datagram protocol (UDP) based applications suffer high packet loss as well as out-of-order delivery. This is due to the high bit error rate (BER) nature of the wireless links and the high mobility of...
We consider a cognitive radio network in which a set of base stations make opportunistic spectrum access to support wireless subscribers within their covering cells. The spectrum of interest is divided into independent channels licensed to the primary users. Channel assignment and power control must be carried out in the cognitive network so that no excessive interference is caused to the primary...
We consider multiple-input multiple-output (MIMO) radar systems with widely spaced transmit and receive antennas. We treat the problem of detecting point targets when one or more target parameters of interest are unknown. We provide a composite hypothesis testing framework for jointly estimating such parameters along with detecting the target while only a finite number of signal samples are available...
Future military operations will feature network-enabled human soldiers working seamlessly with intelligent, autonomous systems such as sensor networks and unmanned vehicles. In these systems, data aggregation (e.g., data fusion, plan monitoring) and data dissemination (e.g., information sharing) will be essential communication patterns. While ad hoc networks are commonly proposed for complex battlefield...
We have added a restricted subset of probabilistic reasoning to our deterministic adversarial reasoning technique, RAPSODI. This hybrid approach strikes a balance between the intractable complexities of computing a fully probabilistic representation, versus the inadequate expressiveness of a simpler deterministic representation. After a brief review of the basic adversarial planning algorithm, we...
We develop accurate and robust one-dimensional EXIT chart methods to design raptor codes with binary and higher-order modulations on AWGN channels over any desired range of SNRs. We formulate the check-node degree distribution optimization as a linear program that optimizes a suitable objective function of the desired operating points. The throughput curves predicted by the analysis are easily compared...
Statistics that are obtained from the demodulator are used in a direct-sequence spread-spectrum receiver to provide an estimate of the signal-to-noise ratio. We evaluate the applicability to spread-spectrum multiple-access systems of an SNR estimator that was proposed previously for SNR estimation in systems for which the only disturbance is thermal noise. The proposed estimate does not require the...
This paper examines rendezvous protocols for ad hoc network establishment in cognitive radio networks. Such capability is needed when deploying cognitive radios in an area whose existing fixed communications infrastructure has been destroyed, such as after a natural disaster. A review of previous rendezvous strategies reveals the need for more research and analysis on the multi-channel, asynchronous...
Mobile free space optical (FSO) links suffer from frequent link blockages due to opaque obstructions or link degradations that can result in degraded or failed networks. In this paper, a dynamic layer-1 based topology and routing control methodology is presented for assuring connectivity in networks with fragile links. Core components of this methodology are described with special emphasis on the...
In this paper, we present the design, implementation, and evaluation of a custom-built wideband RF front-end for enabling dynamic spectrum access communications in software-defined radio platforms. The frontend is designed for wireless operation within the 50 MHz - 2.5 GHz frequency range, and is entirely software-controlled by the platform. Evaluation of the proposed design was conducted using the...
As the world becomes increasingly dependent on dynamic and up-to-the-moment information, we recognize that broadband networks must be able to convey this information timely and wirelessly, to and from users in motion. Varieties of 802.11 compliant equipment and other types of broadband wireless equipment have been proposed for, and in some areas, being used to meet this need. There have been questions...
A blueprint for an experimental low-power communications device (wireless mote) suitable for ad-hoc and networking applications is presented. The proposed device implements a random access packet-based communications protocol that exploits a special packet structure which is composed of separate header and payload portions. To enable robust packet detection, the headers consist of a preassigned spreading...
The performance of a serially concatenated convolutional code (SCCC) for frequency hopped M-ary phase shift keying communication systems over an additive white Gaussian channel noise (AWGN) in the presence of a partial-band noise jammer is discussed in the paper. The scaling of the log-likelihood ratio (LLR) which improves the SNR dynamic range and the jamming strategy are also discussed in the paper...
Military force structures are becoming increasingly complex and net-centric as new technologies are developed and deployed. As such, there is an ever increasing need to provide system-of-systems (SoS) analysis tools to assist in evaluating a military combat team's survivability, lethality, sustainment and logistics. Evaluation of networked communications as part of this analysis is often overlooked...
A future satellite communications system is envisioned that will provide a number of enhancements over predecessor satellite communication systems. It will employ high capacity packet switched service in space, high rate circuits between terminals, and utilize Dynamic Bandwidth Resource Allocation which dynamically assigns resources to terminals based on current channel conditions and traffic demand...
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