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Synthetic aperture radar (SAR) is a form of imaging radar. The defining characteristic of SAR is the usage of relative motion between an antenna and its target region to provide long-term coherent-signal variations that can be exploited to obtain fine spatial resolution for radar image. Due to the improvement of SAR data acquisition technique and the flexibility of SAR sensor deployment, multi-pass...
A Cognitive Radio Network (CRN) based Wireless Sensor Network (WSN), as an extension of CRN, is explored for radio frequency (RF) passive target intrusion detection. Compared to a cheap WSN, the CRN based WSN is expected to deliver better results due to its strong communication functions and powerful computing ability. Issues addressed in this paper include experimental architecture, waveform design,...
In this paper, a novel approach based on non-negative matrix factorization is applied for joint spectrum sensing and primary user localization in cognitive radio networks. This approach is robust and tolerant to sparse, yet strong interference caused by malicious attack or false data injection. Simulation results clearly indicate that the proposed method is highly effective in yielding low localization...
This paper, one in a series on new initiatives in wireless tomography, combines two areas: wireless communication and radio tomography. This paper discusses implementation of wireless tomography in a distributed architecture. Each sensor node in the wireless tomography system solves the local optimization problem to get the image and shares its own imaging result to all the other sensor nodes. The...
We propose a prototype system for wireless tomographic imaging using commercially available software defined radio systems. The proposed architecture utilizes USRP2 systems as sensor nodes. The USRP2 system is evaluated as a means of accurately measuring attenuation for use in self-coherent tomography. The potential error and its impact on the accuracy of our proposed system is explored.
This is the following paper in a series on a new initiative of wireless tomography. The goal is to combine two areas: wireless communication and radio tomography. This paper primarily focuses on phase reconstruction using machine learning for wireless tomography. When only communication components instead of sophisticated equipment are exploited to perform wireless tomography, phase information of...
In order to be viable for use in communication and radar systems, wideband beamforming requires the calculation of filter coefficients to be performed quickly so as to avoid undesirable latency in the system. This paper provides a quick introduction to the method of least-squares wideband beamforming and discusses the use of General Purpose computation on Graphics Processing Units (GPGPU) for acceleration...
Cognitive radio has been put forward to make efficient use of scarce radio frequency spectrum. A testbed for cognitive radio can not only verify concepts, algorithms, and protocols, but also dig out more practical problems for future research. However, to our best knowledge, an authentic real-time cognitive radio system has never been demonstrated. In order to build a cognitive radio network testbed,...
Response delay problem and measurements of such delays have been reported in Part I. The response delay has a negative impact on the accuracy of spectrum sensing, which is the cornerstone of cognitive radio. In this paper, single-user prediction of channel state is proposed to minimize the negative impact of response delays caused by hardware platforms. Specifically, a modified hidden Markov model...
This paper reports a research testbed of real-time ultra-wideband (UWB) multiple-input multiple-output (MIMO) radio. In the receiver design, the UWB MIMO receiver supports up to eight channels, where each channel is equipped with an analog-to-digital converter (ADC) with 8-bit resolution and sampling rate up to 3 Giga samples per second (Gsps). The transmitter is able to transmit two independent arbitrary...
Cognitive radio has been put forward to make efficient use of scarce radio frequency spectrum. Once available frequency bands have been detected using spectrum sensing algorithms, spectrum auction can be employed to allocate the detected available frequency bands to secondary users. In this paper, a bidding algorithm based on Q-learning for secondary users is proposed. Secondary users employ the proposed...
Denial-of-service (DoS) attack is a serious threat to the communication networks in smart grid, which may result in severe instability of power systems. A jammer can send strong interference to jam the data transmission if wireless communication systems are used for conveying system state information from a remote sensor to a controller in the wide area system monitoring and control. When being jammed...
In smart grid, a home appliance can adjust its power consumption level according to the realtime power price obtained from communication channels. Most studies on smart grid do not consider the cost of communications which cannot be ignored in many situations. Therefore, the total cost in smart grid should be jointly optimized with the communication cost. In this paper, a probabilistic mechanism of...
Spectrum sensing detects the availability of the radio frequency spectrum in a real-time fashion, which is essential and vital to cognitive radio. The requirement for real-time processing indeed poses challenges on implementing spectrum sensing algorithms. Trade-off between the complexity and the effectiveness of spectrum sensing algorithms should be taken into consideration. In this paper, a fast...
Secure system state estimation is an important issue in smart grid to assure the reliability and security. In this paper, the case of a single observation station and Gaussian noise communication channel with an eavesdropper is considered. The channel capacity requirement is studied from the information theoretic perspective. The smart grid is modeled as a linear dynamic system. Then, the channel...
This paper discusses the theory behind ultrawideband (UWB) transmit waveform design, and reports a proof-of-concept UWB radio testbed with waveform level precoding. Unlike a narrow-band channel, a UWB channel contains a large number of resolved multipath components, which opens a door for exploring new features offered by UWB. Waveform level optimization is meaningful, but it is a great challenge...
In this paper, a testbed design and implementation of ultra-wideband (UWB) multiple-input single-output (MISO) time-reversal system are presented. The implementation is based on field programmable gate array (FPGA). The combination of MISO with UWB time-reversal is promising for enhancing the data rate and reliability in harsh wireless environments. When multiple transmitter antennas are considered...
Wireless tomography, a novel approach to remote sensing, is proposed in Part I of this series. The methodology, literature review, related work, and system engineering are presented. Concrete algorithms and hardware platforms are implemented to demonstrate this concept. Self-cohering tomography is studied in depth. More research will be reported, following this initiative.
This is the second paper in a series on a new initiative of wireless tomography. The goal is to combine two areas: wireless communication and radio tomography. This paper studies wireless tomography from a system engineering's point of view. Machine learning and waveform diversity will be applied to wireless tomography. The potential system architecture for wireless tomography will also be given.
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