The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In heavy traffic cellular networks low priority handover requests will increase handover drops. In current handover queuing schemes, slow signal strength changing mobile units with low priority handover requests can occupy the handover queue space. As a result, high priority requests will be dropped. This effect could be eliminated utilizing a new scheme called comparative queuing. Prioritization...
In this paper, a general fading model for wireless communications is introduced describing the nonlinearity, and at the same time the non-homogeneous nature of the propagation medium. Namely, the a - lambda - mu - eta includes the a - mu , the lambda - mu, the eta - mu, the gamma, the exponential, the Weibull, the Hoyt, the Nakagami-m, the Rayleigh, and the one-sided Gaussian distributions as special...
In wireless systems, a relay station (RS) is introduced to overcome capacity degradation in a shadowing area or a cell edge. Various relay schemes have been proposed to improve capacity by increasing link quality and diversity gain. However, there is no study about relay scheme in multiple cooperative relay network environments which means that more than one RS are cooperatively operated in same domain...
Broadcast is one of the most fundamental services in wireless sensor networks (WSNs). It facilitates sensor nodes to propagate messages across the whole network, serving a wide range of higher-level operations and thus being critical to the overall network design. A distinct feature of WSNs is that many nodes alternate between active and dormant states, so as to conserve energy and extend the network...
Due to the unsupervised nature of wireless sensor networks (WSNs), intensive communications are required among the selected nodes to reach a consensus and synchronize prior to entering a distributed beamforming (DBF) procedure. Therefore, a sensible approach to select the nodes should not only take into account the required beampattern, but also should aim to preserve the inter-node connectivity and...
Common localization approaches require a large amount of information to be available in order to achieve identifiability, when the signal propagates in a strictly Non-Line-of-Sight (NLOS) environment. Furthermore, even if they achieve identifiability, they usually perform poorly. In this contribution we investigate the conditions that must be met for identifiability to be feasible and for performance...
This paper considers the problem of target location estimation in a wireless sensor network based on IEEE 802.15.4 radio signals and proposes a novel implementation of the maximum likelihood (ML) location estimator based on the Cross-Entropy (CE) method. In the proposed CE method, the ML criterion is translated into a stochastic approximation problem which can be solved effectively. Simulation results...
The benefits of Amplify-and-Forward (AF) and Decode-and-Forward (DF) cooperative relay for secure communication are investigated within Wyner's wiretap channel. We characterize the secrecy rate when source, destination, relay and eavesdropper all use single antenna and the channel conditions are fix. Both AF and DF cooperative strategies are proved theoretically to be able to facilitate secure communication...
Selection relaying is a promising technique for practical implementation of cooperative systems with multiple relays. However, to select the best relay, globe channel knowledge is required at the selecting entity. In this paper, we consider the relay selection problem in dual-hop amplify-and-forward (AF) communication systems with partial channel state information (CSI). We present relay selection...
Collaborative sensing in cognitive radio networks can significantly improve the probability of detecting the transmission of primary users. In current collaborative sensing schemes, all collaborative secondary users are assumed to be honest. As a consequence, the system is vulnerable to attacks in which malicious secondary users report false detection results. In this paper, we investigate how to...
Compressive sensing is a revolutionary idea proposed recently to achieve much lower sampling rate for sparse signals. For large wireless sensor networks, the events are relatively sparse compared with the number of sources. Because of deployment cost, the number of sensors is limited, and due to energy constraint, not all the sensors are turned on all the time. In this paper, the first contribution...
Wireless geolocation problems based on received signal strength (RSS) are discussed in this paper. Using the maximum likelihood based range estimates, a new distributed and iterative linear combination location estimator is proposed. In a non-cooperative case where unknown-location (blindfolded) devices only utilize the power measurements from known-location devices (anchors), the proposed algorithm...
Extensive studies have been carried out for reducing the handover time of wireless network at medium access layer (MAC). However, none of them depicts the impact of reduced handover time on the overall performance of wireless networks. This paper presents the methodology that can be used to effectively reduce the handover time. Our proposed model incorporates many critical performance measurements...
In this paper, we analyze the impedances seen by each amplifier under the active load pulling in Chireix combiner. We derive the analytical expressions for the impedances and prove them in Agilent ADS software. From these expressions, we propose an impedance match method to improve the efficiency of the Chireix impedance using LoadPull simulation in ADS.
Design of a dual-band branch line coupler with a very compact size is proposed. For reducing circuit area, stepped-impedance sections are used. Folded open stubs are attached to each stepped-impedance section at its both ends for the dual-band purpose. Circuit dimensions and geometrics are designed in order to achieve the best circuit miniaturization. For validation, measured results of an experimental...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.