[Show abstract][Hide abstract] ABSTRACT: A novel fiber Bragg grating direct current sensor with intrinsic temperature compensation is presented in this article. The operating principle of the sensor is based on the deflection of a cantilever beam due to the electromagnetic force between a static-iron and a moving-iron attached to the free end of the cantilever which is enclosed within a solenoid through which the current under test is passed. The deflection of the cantilever beam is measured by differential strain sensing using two fiber Bragg gratings mounted on either side of the beam, thus achieving temperature compensation. The sensor operation is theoretically described, and experimental measurements confirm the operation of the fiber Bragg grating direct current sensor up to 500 A. A 382-pm Bragg wavelength shift difference is detected when the current is 500 A. The test results are analyzed and discussed in the time domain and frequency domain. The resistance to electromagnetic interference immunity of the fiber Bragg grating sensor is improved compared with the strain gauge sensor.
Full-text · Article · Mar 2015 · Advances in Mechanical Engineering
[Show abstract][Hide abstract] ABSTRACT: This paper considers a opportunistic relay selection scheme for a cooperative and cognitive radio system. In the secondary network, two secondary users (SU) exchange information with each other via an assist relay and share the spectrum with the primary network. By using optimal power allocation among the SUs and relay, we analytically derive the outage probabilities of the secondary network under the constraints of limiting an outage probability of primary network to satisfy a required target. A tight closed-form expression is obtained to evaluate the secondary network performance of opportunistic relay selection. Numerical and simulation results demonstrate the diversity gain over opportunistic relay selection and verify the analysis.
[Show abstract][Hide abstract] ABSTRACT: The next generation wireless network environments are expected to support anywhere, anytime connectivity for high-performance applications. To provide mobile users with seamless wireless access and guaranteed quality of service (QoS), it is a trend to integrate UMTS cellular networks and wireless local area networks (WLANs) into heterogeneous networks in next generation all-IP wireless networks. Access network selection and QoS support for different services are the major challenges in integrated UMTS/WLAN networks. In this paper, we propose a novel access selection method to determine which network is more suitable for a mobile user's service request in heterogeneous UMTS and WLAN networks. This method is utility-based and takes into account QoS requirements of applications, network condition and user mobility. Also it introduces a balancing index in order to reduce the utility value of a network if it is heavily loaded. Consequently, the lower selected probability of the heavily loaded network is obtained. Simulation results demonstrate the improved performance of the proposed access selection scheme as compared with the cost-based scheme. It can reduce new blocking and handoff dropping probabilities, as well as number of handoff. Moreover, this scheme achieves a balance between system utilization and network loading while maintaining QoS requirements. Also larger system throughput is achieved.
No preview · Article · Jan 2012 · International Journal of Advancements in Computing Technology
[Show abstract][Hide abstract] ABSTRACT: In next-generation wireless networks, effective management of the limited radio resources is very important to provide mobile multimedia services with Quality of Service (QoS) guarantees. Many mechanisms based on Bandwidth Reservation (BR) have been proposed to decrease connection blocking/dropping probability. In this paper, we propose an adaptive and dynamic reservation as well as Call Admission Control (CAC) method for multimedia traffic in wireless systems. The analytical results are supported by simulation and show that this work improves the service quality by minimising the new Call Blocking Probability (CBP) and handoff Call Dropping Probability (CDP).
No preview · Article · Mar 2011 · International Journal of Computer Applications in Technology
[Show abstract][Hide abstract] ABSTRACT: In next generation wireless networks, great challenges have been posed to provide mobile multimedia services with QoS guarantees. Since bandwidth is a scarce resource in wireless networks, effective management of the limited radio resources is important to enhance the network performance. In this paper, we propose an adaptive and dynamic resource reservation and call admission control (CAC) scheme for multimedia traffic in wireless systems. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the new call blocking probability and handoff call dropping probability.
[Show abstract][Hide abstract] ABSTRACT: One of the major design issues in wireless overlay networks is the support of vertical handoff. It is becoming essential to offer vertical handoff solutions where users can move among various network types efficiently and seamlessly. Vertical handoff is the switching process between heterogeneous wireless networks. In this paper, we propose and analyze a novel vertical handoff decision strategy that considers the performance of the whole system. This strategy takes into account the network bandwidth, received signal strength (RSS) and variation of RSS. The performance comparison of the proposed vertical handoff decision scheme and existing scheme shows that the proposed scheme can reduce the handoff call dropping probability.
[Show abstract][Hide abstract] ABSTRACT: The measurement of alternating current (AC) is realized by using fiber Bragg grating (FBG), giant magnetostriction material (GMM), and the technology of fiber coupler demodulation (fiber wavelength division multiplexing filter, FWDMF). The magnetostrictive effect of GMM, the theoretical analysis of the FBG current measurement and the interrogation technology of FWDMF are introduced as well. The sensing unit of AC current measurement is constructed with magnetostrictive material and FBG. The feasibility of AC current measurement by using this method is proved, when the AC exciting current is in the scope of 0~2A.
Full-text · Article · Dec 2008 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: One of the major design issues in heterogeneous wireless networks is the support of vertical handoff. Vertical handoff occurs when a user with a multi-interface terminal changes association from one type of wireless access technology to another while maintaining an active session. It is believed that vertical handoff decision will be based on multiple criteria. In this paper, new handoff criteria are introduced along with an improved vertical handoff decision strategy based on fuzzy logic. A performance study using the integration of cellular networks and WLANs as an example shows that our proposed vertical handoff decision algorithm can reduce the handoff call dropping probability as well as unnecessary handoffs in heterogeneous wireless networks.