a Gaussian relationship between the signal intensity and the EDG chip temperature, thus confirming Eq. (6). The measured wavelength values for the five gratings are listed in Table 1 and compared to those provided by the manufacturer. It is noted that the measurement resolution of the interrogator is better than 1 pm as the reading resolution of the EDG chip temperature is better than 0.01°C. It is further observed that the measured wavelengths are in good agreement with those provided by the manufacturer. The small variations in wavelengths can be attributed to environmental disturbances, such as the impact of temperature and strain on the grating. It is well known that Bragg wavelength shifts with temperature at a rate of ϳ13 pm/°C and strain at a rate of ϳ1.2 pm/ for Bragg wavelength of 1550 nm [12].The developed interrogator was also used to monitor temperatures. Figure 7 shows the experimental results of such temperature variation and illustrates the performance of the interrogator for temperature measurement. By monitoring the EDG temperature corresponding to the maximum optical power in a dedicated channel (Channel 19 in this case), the FBG temperature sensor can be precisely interrogated.Through proper design of the EDG and use of current technology, 100 channels or more can be interrogated. Moreover, because of the compactness and light-weight of the interrogator, it is possible to stack several miniaturized interrogators together and increase the interrogator capability beyond the developed device presented here. Thus providing added flexibility and increasing the interrogation capability. We are currently working on employing this technology in an aerospace environment. This device is seen of significant potential in robotics, smart clothing, and security systems application requiring light-weight and compactness. CONCLUSIONSA miniaturized fiber Bragg grating sensor interrogation device based on integrated EDG has been proposed, developed, and prototyped.Results, employing this device, illustrated its performance for temperature measurement and for FBG sensor Bragg wavelength identification. This device is also able to monitor multiFBG sensors simultaneously with a resolution better than 1 pm. REFERENCES1. Kim, In-flight health monitoring of a subscale wing using a fiber Bragg grating sensor system, Smart Mater Struct 12 (2003), 147-155. 2. K. Wood, T. Brown, R. Rogowski, and B. Jensen, Fiber optic sensors for health monitoring of morphing airframes. I. Bragg gating strain and temperature sensor, Smart Mater Struct 9
In the classical B‐Scan ground penetrating radar (GPR) imagery, unprocessed image domain data exhibit undesired hyperbolic effects and therefore have low resolution features. To solve this problem, various focusing or migration techniques have been developed and applied to focus the scattered energy at their true spatial locations in the object space. In this article, we present a synthetic aperture radar (SAR) based focusing algorithm to obtain well‐localized two‐dimensional B‐scan GPR images of various buried objects. The concept and the formulation of our frequency domain based imaging algorithm are presented. The performance of the algorithm is tested with both the simulated and measurement data. The simulation data are generated by a physical optics shooting and bouncing ray (PO‐SBR) technique code; whereas the C‐band measured data are collected via an experimental set‐up for different ground environments. Almost perfect focusing performance is achieved for the simulated GPR images. Similarly, well‐focused GPR images with high lateral resolutions are also obtained for the measurement data from metallic and non‐metallic buried objects. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2534–2540, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22724
In the next-generation wireless networks, cooperative communication is one of the auspicious techniques through which spatial diversity could be achieved by permitting the single antenna to act as virtual multiple input multiple output (VMIMO). The fundamental principle of cooperative communication was established on different types of relaying protocols and implementation of different relaying protocols according to the requirements of communication scenarios. The challenging task for achieving a high performance in cooperative communication is to find out the optimal relay node (RN) among different prevailing RNs. The basic purpose of cooperative communication is to maximize the performance of the network and minimize the overhead triggered by RNs by considering different communication metrics, i.e., signal to noise ratio (SNR), channel state information (CSI), and bit error rate (BER). This study presents a review of different cooperative relaying protocols with best relay selection techniques in the next-generation wireless network. Moreover, the different challenges faced by millimeter wave in 5G wireless networks and the role of cooperative communication to overcome those challenges are discussed. Turkey is that it transmits the duplicates of a signal to the destination independently. Many ideas regarding cooperative communication were first derived by Nichola et al. [5]. In the next-generation wireless network, cooperative communication may be one of the promising approaches for achieving the high data rates as well as efficient utilization of the bandwidth. Cooperative communication uses a RN, to provide coverage in the holes within the Long-Term Evolution-Advanced (LTE-A) cellular networks [6]. Similarly, in mm-wave communication that is considered in 5G, the relaying techniques are used to overcome different challenges of link blockage, backhaul connectivity, and path loss etc. Moreover, to make this technology more efficient and reliable, further improvements are required to achieve these goals.This study presents a broad overview of different relaying protocols with optimal relay selection methods used in different wireless networks. In addition, this study presents the potential benefits of using cooperative communication to overcome different challenges faced by the next generation of wireless networks. The remainder of this article is organized as follows. Section 2 presents existing research on cooperative communication. Section 3 gives an overview of cooperative communication, in which different relaying protocols are presented and comparison between them. In Section 4, we discuss the review of optimal relay selection techniques. In Section 5, we explain the different challenges faced by mm-wave and how to overcome them by cooperative communication. Section 6 summarizes the future challenges in cooperative communication and finally the conclusion is given in Section 7. Sami et al. [7] demonstrate a survey and taxonomy on medium access control for cooperative communication. This study classifies ...
We introduce a novel sensor node management and location estimation method referred as sectoral sweeper (SS) scheme that uses an adaptive antenna array (AAA) at a central node in wireless sensor networks (WSNs). With the SS scheme, the central node can activate or deactivate the nodes in a desired region which is specified by beam direction and beam width of the transmit beam and also by minimum and maximum thresholds (R min and R max ) for the received signal strength indicator (RSSI) of signals received by the nodes. In order to perform a specified task that is associated with a Task id, two different beams are transmitted, which are task region beam and routing region beam to switch the nodes into active or routing modes. Since our scheme does not require any additional software or hardware for node management and location estimation in sensor nodes, the deficiencies of tiny sensors are effectively eliminated. The proposed scheme is shown to reduce the number of sensing nodes and the amount of data traffic in the network, thus leading to considerable savings in energy consumption and prolonged sensor lifetime.
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