This paper introduces sage - an algorithm that uses the spatial clustering of objects to enhance their classification. It assumes that discrete objects can be identified and classified based on their individual appear...
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ISBN:
(纸本)9781424441211
This paper introduces sage - an algorithm that uses the spatial clustering of objects to enhance their classification. It assumes that discrete objects can be identified and classified based on their individual appearance, and further that they tend to appear in spatial clusters (for example, circinate exudates). The algorithm builds spatial distribution maps for objects and confounds for a given image, and adjusts individual object confidence levels to reflect their spatial clustering. sage may be combined with a wide range of object identification and classification methods;we demonstrate it using a Multi-Layered Perceptron (MLP) Neural Network and a Support Vector Machine (SVM) classifier types for both dark and bright retinal lesions. Using ROC analysis sage improves classifier performance as much as 83%.
In this paper, by using a multiple-input multiple-output (MIMO) antenna array, a channel measurement campaign in outdoor environments is introduced. The measurement campaign captures the spatial characteristics of cen...
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ISBN:
(纸本)9781509016990
In this paper, by using a multiple-input multiple-output (MIMO) antenna array, a channel measurement campaign in outdoor environments is introduced. The measurement campaign captures the spatial characteristics of centimeter wave (cm-wave) propagation at the center frequency of 26 GHz. By using the parametric approach of the Space-Alternating Generalized Expectation-maximization (sage) algorithm, the channel characteristics in the delay and spatial domains are extracted, and compared with the channel model below 6 GHz. Our analysis shows that the channel dispersions in the delay and directional domains are smaller at the 26 GHz. Furthermore, single-user (SU)-MIMO and multi-user (MU)-MIMO channel matrix properties are investigated, and show that the MU-MIMO channel has good orthogonal property. It implies that MU-MIMO will be one promising MIMO technique in cm-wave band.
Three dimensional (3D) Multiple Input Multiple Output (MIMO) is considered as one key technology for 5th Generation mobile communication systems. However, can the capacity derived from a 3D channel impulse response (C...
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ISBN:
(纸本)9781509018918
Three dimensional (3D) Multiple Input Multiple Output (MIMO) is considered as one key technology for 5th Generation mobile communication systems. However, can the capacity derived from a 3D channel impulse response (CIR) better approximate the corresponding capacity derived from the measured CIR? Is there a substantial improvement in the capacity of 3D MIMO system in comparison to the classical 2D case? To answer these questions, extensive field measurements were conducted for the outdoor to indoor scenarios in China and New Zealand. Key channel parameters are extracted from the measured channel impulse response via the space-alternating generalized expectation-maximization algorithm, followed by the reconstruction of the 32 × 56 CIR according to 2D and 3D channel model. Then CIRs are used to evaluate the channel capacity and comparative simulation results demonstrate that the 3D MIMO capacity closely approximates the capacity predicted with practical CIRs. Moreover, obvious enhancements in the capacity of 3D channel is observed in comparison to 2D case. In addition, the distribution of eigenvalues and the number of contributing eigenvalues are also investigated.
This paper presents a novel reduced-complexity channel estimator for multi-user Coordinated Multi-point (CoMP) systems. The proposed scheme is based on Space Alternating Generalized-EM (sage) algorithm combining with ...
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ISBN:
(纸本)9781467318808
This paper presents a novel reduced-complexity channel estimator for multi-user Coordinated Multi-point (CoMP) systems. The proposed scheme is based on Space Alternating Generalized-EM (sage) algorithm combining with the Least Square (LS) criterion. Aiming at the problem that the conventional joint multi-user LS estimator will introduce the complex inversion of large size matrix when using non-orthogonal pilots, the proposed estimator avoids the inverse operation by transforming the joint multi-user estimation into a series of single-user estimating process in an iterative way. Simulation results verify that the proposed algorithm can reduce the complexity while achieving the optimal performance of joint LS channel estimation for the CoMP systems.
In this contribution, a multi-variate probability density function (pdf) is derived and used to describe the normalized direction-(i.e. azimuth and elevation)-delay power spectral density of individual dispersed compo...
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In this contribution, a multi-variate probability density function (pdf) is derived and used to describe the normalized direction-(i.e. azimuth and elevation)-delay power spectral density of individual dispersed components in the response of the propagation channel. This pdf maximizes the entropy under the constraint that its first and second moments are specified. We use a sage algorithm, as an approximation of the maximum-likelihood method, to estimate the parameters of the component direction-delay power spectral densities from measurement data. The experimental results show that the proposed pdf and the sage algorithm form altogether an effective tool to characterize direction-delay dispersion in the propagation channel.
The presence of a frequency offset (FO) and phase noise can cause severe performance degradation in digital communication systems. This work combines a simple FO estimation technique with a low-complexity phase noise ...
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ISBN:
(纸本)9781457713460
The presence of a frequency offset (FO) and phase noise can cause severe performance degradation in digital communication systems. This work combines a simple FO estimation technique with a low-complexity phase noise estimation method, inspired by the space-alternating generalized expectation-maximization algorithm. Using a truncated discrete-cosine transform (DCT) expansion, the phase noise estimate is derived from the estimated DCT coefficients of the phase. A number of implementations of the proposed algorithm are discussed. Numerical results indicate that when estimating the FO from pilot symbols only, comparable performance can be reached as the computationally more complex case where the FO is updated iteratively, with small convergence time. The phase noise estimation step is well capable of compensating for the residual FO. For the considered scenario, performing FO compensation before iterative phase noise estimation yields a bit-error rate performance degradation close to the case where the FO is known.
In a cooperative network, relaying nodes transmit to the destination information that is related to the message sent by the source. In literature the performance of such networks is usually studied under the (unrealis...
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ISBN:
(纸本)9781467325660
In a cooperative network, relaying nodes transmit to the destination information that is related to the message sent by the source. In literature the performance of such networks is usually studied under the (unrealistic) assumption of perfect channel knowledge at the destination. In this paper we consider the Amplify-and-Forward protocol and assume time-varying Rice fading components. Based on pilot symbols an initial estimate of the channel parameters that correspond to the actual channel realizations is obtained, and is subsequently refined in an iterative way by also exploiting the information contained in the data part of the received signals. The iterative estimator gives rise to substantial improvements in terms of error performance and bandwidth efficiency as compared to the initial pilot-based estimate.
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