Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.     

Optimal sensor placement for source localization based on RSSD

Wireless Networks - Source localization based on the received signal strength (RSS) has received great interest due to its low cost and simple implementation. In this paper we consider the source...     

Filter bank SCFDMA: an efficient uplink strategy for future communication systems

This paper develops a generalized system model for the precoded multicarrier communication system, using basic multirate building blocks. Mathematical analysis of the proposed model is carried out, and the results are utilized in developing an efficient uplink wireless communication standard filter bank single carrier frequency division multiple access. The proposed system combines the low peak to average power ratio (PAPR) advantage of a single carrier communication system with the reduced out of band emission (OBE) of filter bank multicarrier (FBMC) scheme. The sensitivity of the proposed system to carrier frequency offset (CFO) is analyzed, and the results are utilized in developing a CFO compensation scheme with reduced complexity. A Nyquist filter design approach, which strikes a balance between OBE and tail size, is developed and is incorporated into the proposed system to enhance the OBE and PAPR characteristics. The instantaneous power of the proposed system is theoretically analyzed using characteristic function based approach, and the effectiveness of modifications is substantiated. A detailed simulation study is carried out to validate the performance of the proposals.     

Design and Analysis of a Channel Assignment Scheme for CDMA/TDMA Mobile Networks

In this paper, a channel assignment scheme is proposed for use in CDMA/TDMA mobile networks carrying voice and data traffic. In each cell, three types of calls are assumed to compete for access to the limited number of available channels by the cell: new voice calls, handoff voice calls, and data calls. The scheme uses the movable boundary concept in both the code and time domains in order to guarantee the quality of service (QoS) requirements of each type. A traditional Markov analysis method is employed to evaluate the performance of the proposed scheme. Measures, namely, the new call blocking probability, the handoff call forced termination probability, the data call loss probability, the expected number of handoff and the handoff link maintenance probability are obtained from the analysis. The numerical results, which are validated by simulation, indicate that the scheme helps meet the QoS requirements of the different call types.     

A NIC with Impedance Scaling Properties Using Unity Gain Cells

A novel negative impedance converter (NIC) is proposed. This configuration is based on unity gain cells (a cascade of current and voltage followers with unity gains). The proposed circuit has wide band impedance scaling property, and it is suitable for practical implementation of realizing high-negative-valued passive components.     

CMOS RF switched capacitor bandpass filter tuned by ring VCO

A new RF switched capacitor bandpass filter and its command circuit made up of a ring voltage controlled oscillator with ‘XOR’ gates are proposed. Implemented in a standard CMOS technology, this circuit is intended to be used in a subset of professional mobile phone applications [380–520 MHz]. Experiments carried out on a prototype show a tunable center frequency range of 260 MHz [240–500 MHz], with a quality factor that can be as high as 300.     

Event Distortion-Based Clustering Algorithm for Energy Harvesting Wireless Sensor Networks

Wireless Personal Communications - Wireless sensor networks (WSNs) consist of compact deployed sensor nodes which collectively report their sensed readings about an event to the Base Station (BS)....     

The influence of substrate temperature on the structural and optical properties of ZnS thin films

Thin films of ZnS were deposited on soda lime glass substrates by a modified close-space sublimation technique. The change in optical and structural properties of the films deposited at various substrate temperatures (150–450°C) was investigated. X-ray diffraction spectra showed that films were polycrystalline in nature having cubic structure oriented only along (111) plan. The crystallinity of films increased with the substrate temperature up to 250°C. However, crystallinity decreased with further increase of substrate temperature and films became amorphous at 450°C. The atomic force microscopy data revealed that the films become more uniform and dense with the increase of substrate temperature. Optical properties of the films were determined from the transmittance data using Swanepoel model. It was observed that the energy band gap is increased from 3.52 to 3.65 eV and refractive index of the films are decreased with the increase of substrate temperature. Moreover, considerable improvement in blue response of the films was noticed with increasing substrate temperature.     

Bayesian Unsupervised Learning for Source Separation with Mixture of Gaussians Prior

This paper considers the problem of source separation in the case of noisy instantaneous mixtures. In a previous work [1], sources have been modeled by a mixture of Gaussians leading to an hierarchical Bayesian model by considering the labels of the mixture as i.i.d hidden variables. We extend this modelization to incorporate a Markovian structure for the labels. This extension is important for practical applications which are abundant: unsupervised classification and segmentation, pattern recognition and speech signal processing. In order to estimate the mixing matrix and the a priori model parameters, we consider observations as incomplete data. The missing data are sources and labels: sources are missing data for observations and labels are missing data for incomplete missing sources. This hierarchical modelization leads to specific restoration maximization type algorithms. Restoration step can be held in three different manners: (i) Complete likelihood is estimated by its conditional expectation. This leads to the EM (expectation-maximization) algorithm [2], (ii) Missing data are estimated by their maximum a posteriori. This leads to JMAP (Joint maximum a posteriori) algorithm [3], (iii) Missing data are sampled from their a posteriori distributions. This leads to the SEM (stochastic EM) algorithm [4]. A Gibbs sampling scheme is implemented to generate missing data. We have also introduced a relaxation strategy into these algorithms to reduce the computational cost which is due to the exponential influence of the number of source components and the number of the mixture Gaussian components.     

Analysis of a new annular multi-slits antenna using wave concept iterative process in cylindrical coordinates

In this paper, a new antenna for satellite applications is proposed. This antenna is designed to operate at any frequency desired. It consists of a circular microstrip patch antenna which incorporates concentric annular slits, and it is printed on a grounded substrate. The details of the proposed antenna design and numerical results are presented and discussed. The wave concept iterative procedure in cylindrical coordinates is used to analyze this new antenna. Using the proposed procedure, less computing time and memory are needed to calculate the electromagnetic parameters of the annular multi-slits antenna.