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Multiple input multiple output (MIMO) space time codes are used to increase the diversity or the number of degrees of freedom for improving the capacity (data rate) and reliability (error rate) of wireless communication over fading channels. In this paper, we propose a new structure of space time code designed for non-stationary constant-amplitude modulation formats using polynomial phase signals...
With the increasing size and complexity of emerging military communication networks, low footprint emulation methods are required to evaluate protocols, algorithms and user performance. In this paper we describe a new emulation architecture that is scalable, modular, and responds to real-time changes in topology and link characteristics. We use this scalable emulation testbed to evaluate system performance...
In this paper, the impact of non-Markovian distributed primary radio (PR) on/off activities on the opportunity time for secondary radio (SR) transmission is studied. The licensed spectrum is partitioned into N frequency bins (FBs) and each primary user is assumed to require only one FB for transmission. The PR activity in each FB is modeled as an independent on/off process. The sojourn time for PR...
A new and novel spread spectrum approach employing orthogonal frequency coding (OFC) for a SAW sensor/tag is presented. This approach provides ultra wide band operation, multi-device interrogation, and reduced loss as compared to conventional SAW CDMA approaches. A traditional SAW CDMA tag consists of an input transducer that launches a surface wave on the substrate towards an array of single frequency...
Approaches to Medium Access Control (MAC) in mobile ad hoc networks (MANETs) can be broadly classified into TDMA and CSMA/CA. In principle, TDMA offers superior performance as well as better capacity guarantees compared to CSMA/CA. In practice, however, the need to provide network-wide synchronization without centralized control, and to accommodate mobility makes TDMA very hard to design and implement...
This work describes an analysis of applying different election heuristics to connected dominated set (CDS) algorithms within different topological graph taxonomies. Our initial motivation for this study was a general observation that a significant amount of research in mobile ad hoc network (MANET) algorithm design and related election heuristic evaluation is based upon geometric random or other types...
During the last decade, intrusion detection systems (IDSs) have become a widely used measure for security management. However, these systems often generate many false positives and irrelevant alerts. In this paper, we propose a data mining based real-time method for distinguishing important network IDS alerts from frequently occurring false positives and events of low importance. Unlike conventional...
In large networks of nodes with mobility, such as certain tactical wireless networks, overall system behaviors can be difficult to predict given the number of interactions between nodes and the number of possible behavior outcomes. Agent-based modeling is seen as an attractive method for representing and analyzing tactical wireless networks. This paper investigates the use of agent-based models to...
The use FPGAs to implement sampled-data FM demodulators for software-defined radios that must support ??legacy waveforms?? is explored and analyzed. Feed-forward and feedback structures are examined. The best feed-forward structure, in terms of the time/area trade-off, is the arctangent-differentiator structure. The arctangent-differentiator and PLL demodulators have approximately the same time/area...
We consider multi-constrained power, rate and channel allocation crafted for low power consumption, delay tolerant traffic, and under interfering link conditions that may be used in a cognitive radio system. Specifically, an iterative distributed algorithm, based on a sum-power constrained sum-rate maximization with upper (and lower) per user and channel power and rate constraints, as well as upper...
A number of Intrusion Detection Systems (IDS) research efforts have demonstrated that network-based attacks can be detected by modeling normal network packet payloads and watching for anomalies. In this paper, we explore a data mining technique based on Principal Component Analysis that can identify specific features within packet payloads that are highly representative of the network traffic. of...
Hierarchical key management schemes would serve well for military applications where the organization of the network is already hierarchical in nature. Most of the existing key management schemes concentrate only on network structures and key allocation algorithms, ignoring attributes of the nodes themselves. Due to the distributed and dynamic nature of MANETs, it is possible to show that there is...
Leveraging the Defense Information Systems Agency's (DISA) experience on the Tactical Services Provider (TSP) Joint Capability Technology Demonstration (JCTD), this paper analyzes the security weaknesses and vulnerabilities of mobile Worldwide Interoperability for Microwave Access (WiMAX) in the TSP architecture and explains DISA's approach to deploying an integrated, multi-layer Information Assurance...
In this paper we study the problem of active eavesdropping in fast fading channels. The active eavesdropper is a more powerful adversary than the classical eavesdropper. It can choose between two functional modes: eavesdropping the transmission between the legitimate parties (Ex mode), and jamming it (Jx mode) - the active eavesdropper cannot function in full duplex mode. In this paper we only consider...
Multiple antenna systems have been shown to provide significant performance improvements for network nodes; however, the vast majority of nodes in military networks will be limited to single channel devices due to mobility (size and power) and ease of use considerations. In this paper we apply a new joint synchronization-pilot sequence (JSPS) optimization design technique to multiple transmitter OFDM...
Dynamic spectrum access (DSA) provides a more flexible spectrum management method versus the current command and control method and promises much higher spectrum utilization efficiency. By this paradigm, secondary users can use vacant spectrum while guaranteeing non-interference to incumbent users. Therefore, spectrum awareness is a required function in DSA, and cooperative spectrum sensing is widely...
In this paper a communication system operating over a Gilbert-Elliot channel is studied. The goal of the transmitter is to maximize the number of successfully transmitted bits. This is achieved by choosing among three possible actions: (i) betting aggressively by using a weak code that allows the transmission of a high number of bits but provides no protection against a bad channel, (ii) betting conservatively...
Many commercial and military systems use some form of random access. ALOHA type protocols are particularly useful for multicast traffic and have low complexity; however, they suffer from low capacity and large loss probabilities. The inclusion of packet level erasure coding in single channel ALOHA protocols is a new area. This paper demonstrates a novel combination of a medium access layer tailored...
Modern tactical networks play an important role in success on the battlefield. Unfortunately, performance evaluation of tactical networks is cumbersome because of the scale and complexity of the underlying systems involved and the cost of deploying large numbers of systems and personnel. Simulation of the tactical network system is sound in theory; but in practice it is extremely difficult to build...
The capacity of a multipoint MIMO wireless network is interference-limited. In order to increase the system capacity, MIMO precoding at the transmitter and decoding at the receiver can be employed so that interference among different nodes is eliminated or suppressed. In this paper, we propose precoding/decoding techniques based on an iterative zero-forcing approach. By utilizing the extra degrees...
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