A novel wideband dynamic directional indoor channel model based on a Markov process

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Capacity Improvement and Analysis of VoIP Service in a Cognitive Radio System

Abstract-We herein analyze the capacity of voice over IP (VoIP) and propose a new method for finding the minimum detection and false-alarm probabilities to ensure the quality-of-service (QoS) requirement of VoIP users in a cognitive radio system. We propose a model for the system supporting the VoIP service as a 2-D discrete-time Markov chain (DTMC). The VoIP traffic and wireless channels in the cognitive radio system are described as a Markov-modulated Poisson process (MMPP) model and a Markov channel model, respectively. In addition, we introduce a simple spectrum-sensing model based on energy detection. By means of the DTMC approach, we demonstrate various analytical and simulation results under the constraint of imperfect spectrum sensing, such as the packet dropping probability, average throughput, and VoIP capacity

An optimal multiedge detector for SAR image segmentation,”

Abstract-Edge detection is a fundamental issue in image analysis. Due to the presence of speckle, which can be modeled as a strong, multiplicative noise, edge detection in synthetic aperture radar (SAR) images is extremely difficult, and edge detectors developed for optical images are inefficient. Several robust operators have been developed for the detection of isolated step edges in speckled images. We propose a new step-edge detector for SAR images, which is optimal in the minimum mean square error (MSSE) sense under a stochastic multiedge model. It computes a normalized ratio of exponentially weighted averages (ROEWA) on opposite sides of the central pixel. This is done in the horizontal and vertical direction, and the magnitude of the two components yields an edge strength map. Thresholding of the edge strength map by a modified version of the watershed algorithm and region merging to eliminate false edges complete an efficient segmentation scheme. Experimental results obtained from simulated SAR images as well as ERS-1 data are presented. Index Terms-Edge detection, multiedge model, region merging, segmentation, speckle, synthetic aperture radar (SAR), watershed algorithm

An Efficient and Simple Method for Designing Prototype Filters for Cosine-Modulated Pseudo-QMF Banks

Abstract-We present a new method to design prototype filters for conventional cosine-modulated pseudo-quadrature mirror filter (QMF) banks. This method is based on windowing, and sets the 3-dB cutoff frequency of the filter obtained at 2 . In this way, the filter bank performance can be significantly improved compared to other existing design methods

A. Lossy Correlated Data Gathering

Abstract — Sensor networks measuring correlated data are considered, where the task is to gather data from the network nodes to a sink. A specific scenario is addressed, where data at nodes are lossy coded with high-resolution, and the information measured by the nodes has to be reconstructed at the sink within both certain total and individual distortion bounds. The first problem considered is to find the optimal transmission structure and the rate-distortion allocations at the various spatially located nodes, such as to minimize the total power consumption cost of the network, by assuming fixed nodes positions. The optimal transmission structure is the shortest path tree and the problems of rate and distortion allocation separate in the high-resolution case, namely, first the distortion allocation is found as a function of the transmission structure, and second, for a given distortion allocation, the rate allocation is computed. The second problem addressed is the case when the node positions can be chosen, by finding the optimal node placement for two different targets of interest, namely total power minimization and network lifetime maximization. Finally, a node placement solution that provides a tradeoff between the two metrics is proposed. Index Terms — sensor networks, energy efficiency, shortest path tree, high-resolution rate-distortio

Spatio-Temporal Channel Characterization in a Suburban Non Line-of-Sight Microcellular Environment

Abstract-This paper reports a spatio-temporal channel characterization of a suburban non line-of-sight microcellular environment in which azimuth-delay profiles obtained by the experiment are compared with ray-tracing simulation. The results are statistically treated step by step to extract model parameters in order to characterize the spatio-temporal channel. The experimental results we obtain are used to improve the accuracy of the simulation process. We are able to obtain a very good agreement between the simulation and the experiment, with the exception of the exponential decay of the delay profile. The results presented in the paper can be directly used to implement the stochastic spatio-temporal channel model, based on the deterministic ray-tracing simulations. Index Terms-Land mobile radio propagation factors, multipath chanels, ray tracing

Co-Channel Interference Mitigation Detectors for Multirate Transmission in TD-CDMA Systems

Abstract-In this paper, we address the problem of downlink detection in a mobile radio time division/code division multiple access multirate communication system employing a linear modulation. We focus on the detection of a group of intracell codes (ranging from a single one to all the active codes) rejecting both interference coming from the complementary set of undesired intracell codes and co-channel intercell interference. We investigate efficient implementations of linear nonadaptive multiuser detection realized by either joint or separate intersymbol interference and multiple access interference (MAI) mitigation using the zero-forcing or minimum mean square error criteria. The proposed detection schemes employ a tunable-complexity structured description of the MAI for the purpose of detection and interference mitigation. Specifically, the receivers always envision an intracell interference mitigation and data detection capability, while intercell interference is treated differently depending on operating environments. If a statistical description of the intercell interference is available, the receiver realizes group detection in the presence of possibly nonwhite Gaussian noise. Soft hand-over procedures are also proposed wherein direct suppression of intercell interference is possible as well as group detection of the data of the neighboring cells. A unified and finite complexity implementation of the proposed detection schemes based on a sliding window formulation is provided. The numerical results validate the proposed receiver structures showing that a structured description of the observation always leads to a detector with superior performance. Index Terms-Code division multiaccess, interference suppression, land-mobile radio cellular systems

Exact maximum likelihood estimation using masked system data,

Reader Ai dssGeneral purpose: Advance state of the art Special math needed for explanations: Elementary probability Special math needed to use results: Same Results useful to: Reliability analysts & researchers distribution, and installation processes. Because of [these advantages, companies are beginning to implement computer plans designed to track such system life data and generate component reliability estimates [9]. In practice, however, this type of analysis is often confounded by the problem of masking, viz, the exact cause of system failure is unknown. This occurs frequently in complex systems and in field data where the failure cause might be isolated only to some subset of components, such as a circuit card containing many individual components. The quantities observed are then: 1) the lifelength of the system, and 2) partial information on the cause of failure. for the general of a series system of3 exponentid components with independent mask-for a SpeCial-CaSe: l-out-of-3:F System Of exponential COming. Their previous work shows that closed-form MLE are intractable, and they propose an iterative method for the solution of a system of 3 non-linear likelihood equations. They do not, however, prove convergence for their iterative method. As such, we show how this system of non-linear equations can be replaced by a single quartic equation, whose solution is straight-forward. Since it does not depend upon the convergence of numerical solution algorithms, the results are exact. Though the resulting estimators are somewhat lengthy & cumbersome to fund manually, they can be written as a straightforward computer code. The calculations can then be easily performed on a personal computer. This method for reducing the likelihood equations to simpler-to-solve forms can be extended readily to a higher number of components. In many cases for more than 3 components it is easier while for others it is more complicated; even in the more complicated cases, this simplification makes the problems much more tractable