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Opportunistic Spatial Orthogonalization (OSO), first proposed in Shen and Fitz (2009) for the single-input-multiple-output (SIMO) system, is a cognitive radio scheme that opportunistically allows the existence of secondary users even if the primary user occupies all the frequency bands all the time. On one hand, OSO can be viewed as a multi-user diversity scheme that exploits the channel randomness...
As advanced communications techniques reach capacity, have reduced performance or system availability, or become unusable, the warfighter must have a reliable, high-capacity communications system in place and standing ready to supplant the degrading systems. Events in the recent past have shown satellites vulnerable to a number of ills or potential problems that could be debilitating. This paper addresses...
With the continuing launch of the wideband global satellite communications (WGS) constellation, the Department of Defense (DoD) will have the opportunity to transition many existing military satellite communications networks from commercial satellite bandwidth to the military-owned satellite resources. Transition to WGS will provide the warfighter with additional capacity to augment future satellite...
In this paper, we introduce a new denial-of-service attack on wireless networks: low-power, distributed jamming network (DJN). DJN is composed of large number of low-power jamming devices, which are deployed in proximity to the target devices. DJN can cause significant damage to target network performance with high energy efficiency. In the paper, we provide a characterization of DJN, demonstrate...
In military tactical communications, cognitive radio (CR) has been proposed as a potential technology. A CR network can support vital communications among troops and vehicles in an alien territory with unfamiliar or unknown radio environment that may be changing dynamically in time. We propose a new approach for dynamic detection of ??white spaces?? i.e. available radio channels, based on a novel...
We propose a two-tier hierarchical wireless sensor network (WSN) to address the mobile multi-target tracking (MMTT) problem. We develop the cluster head (CH) and cluster member election schemes using a particle cardinality balanced multi-Bernoulli (CBMeMBer) filtering algorithm. Under our proposed schemes, the CHs with better views of the tracked targets are activated at each time step and fuse their...
With last year's activation of US African Command (AFRICOM), the United States will now address its security concerns for that turbulent continent with operations realigned under one command instead of three. Information operations will necessarily dominate the Department of Defense's activities in Africa - genocide, poverty, famine, epidemic and civil war are rarely if ever amenable to solution by...
Cooperative relaying has been proposed as a promising technology to provide reliable high data rate services for future wireless networks. The work presented here focuses on a novel efficient three time-slot approach using rateless codes, opportunistic fountain (OF), for cellular networks with fixed relays. This scheme enjoys benefits from both relay selection and inter-relay cooperation, offering...
Statistics obtained during demodulation are used in a direct-sequence spread-spectrum packet radio network to govern the adjustment of transmitter power within the first few packets of a session. The statistics are also employed by an adaptive transmission protocol to select the modulation parameters and the rate of the error-control code for each packet. The power-adjustment protocol uses the statistics...
This paper presents the ultra-wideband (UWB) channel measurement and modeling for an intra-vehicle environment. The measurement was conducted in time domain beneath a commercial vehicle chassis. Channel data were collected at the same locations for the car in stationary and in moving status. Stochastic tapped delay line model is used to characterize the channels in both cases. Slightly larger number...
The Link-16 is the tactical data link utilized by the Joint Tactical Information Distribution System (JTIDS). The JTIDS system is important due to its wide use by U.S. armed forces, NATO, and other allied militaries. Link-16 is a hybrid frequency-hopped/direct sequence spread spectrum system that utilizes minimum-shift keying (MSK) to modulate the chips, cyclical code-shift keying (CCSK) to modulate...
The robustness to jamming signal is an important property for military communication systems. Some previous work has shown that the frequency domain code division multiplexing (CDM) efficiently rejects the interference. In general, however, the jamming signal has higher power than ordinary interference which leads to insufficient jamming rejection performance of these schemes. To mitigate this insufficiency,...
Existing cooperative communications protocols are designed with the assumption that users always behave in a socially efficient manner. This assumption may be valid in networks under the control of a single authority where nodes cooperate efficiently to achieve a common goal. On the other hand, in commercial wireless networks where nodes are individually motivated to cooperate, the assumption that...
We present here an exploration of enabling MIMO spatial multiplexing in a long range LOS point-to-multipoint link such as might be found in a ground-to-air sensor network backhaul or LOS cellular configuration. The paper focuses on the capacity between a single multi-antenna sensor and an airborne multi-antenna transceiver, facilitated by an airborne single-antenna repeater. The multi-point aspect...
Secure operation of mobile ad-hoc networks requires the ability to track the flow of traffic through the network. Knowledge of the path of a packet allows inference of correct operation or potential attacks. In prior work, we have described a number of different techniques for recording such path information and ensuring its correctness through cryptographic techniques. In this paper, we evaluate...
A method that uses the parabolic equation (PE) model to characterize the transmission channel for wideband waveforms is discussed. The results presented use the Advanced Propagation Model (APM) developed by the Atmospheric Propagation branch at the SSC Pacific which utilizes the split-step Fourier algorithm to solve the PE wave equation for a continuous wave (CW) source. To determine the channel response...
COCOMs and G/RSSCs need the ability to rapidly, accurately, and conveniently perform mobile user objective system (MUOS) communications usage planning and to determine if a particular allocation is sufficient so as to, if necessary, negotiate an adjusted apportionment. This paper discusses the design goals of a stand-alone MUOS communication planning application that satisfies these planning objectives...
In this paper, we propose orthogonal frequency division duplex (OFDD) which combines orthogonal division duplex (ODD) and frequency division duplex (FDD) as a new hybrid division duplex scheme. In the asymmetric traffic environment, the mismatch of uplink and downlink between adjacent cells results in co-channel interference (CCI) which degrades the system performance. The proposed scheme can remove...
Motivated by the operational need of eliminating the potential single point of failure (SPOF) of a communications network, a cooperative team communication (CTC) approach is proposed for distributed, wireless sensor and team networks. We assume that the communication system uses a spread spectrum waveform, and each radio implements the Rake processing capability to combat channel fading effects. The...
In this paper, we investigate the information theoretical performance of a cooperative OFDM (orthogonal frequency division multiplexing) system with imperfect channel estimation. Assuming the deployment of a training-aided channel estimator, we derive a lower bound on the achievable rate for the cooperative OFDM system with amplify-and-forward relaying over frequency-selective Rayleigh fading channels...
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