Improving bandwidth efficiency in fault‐tolerant opaque IP over optical mesh networks

Adequately providing fault tolerance while using network capacity efficiently is a major topic of research in optical networks. In order to improve the network utilization, grooming of low‐rate connections in optical networks has been usually performed at the edge of the network. However, in all‐optical networks once a channel is assigned, its entire capacity is dedicated to the users independently of its grooming capabilities. As current users don't usually require such big capacities, bandwidth inefficiencies still occur. In this paper we address this issue introducing unlimited grooming per link (UGPL), a new restoration mechanism for opaque mesh optical networks that grooms connections on a per‐link basis. Simulation results show that UGPL provides the best bandwidth efficiency and the best blocking probability compared to traditional 1 + 1 protection and 1 : N end‐to‐end sharing schemes. Furthermore, we show that the 1 : N end‐to‐end restoration scheme provides no benefits over the simpler and faster 1 + 1 protection scheme. Copyright © 2004 John Wiley & Sons, Ltd.     

AC-coupled front-end for biopotential measurements

AC coupling is essential in biopotential measurements. Electrode offset potentials can be several orders of magnitude larger than the amplitudes of the biological signals of interest, thus limiting the admissible gain of a dc-coupled front end to prevent amplifier saturation. A high-gain input stage needs ac input coupling. This can be achieved by series capacitors, but in order to provide a bias path, grounded resistors are usually included, which degrade the common mode rejection ratio (CMRR). This paper proposes a novel balanced input ac-coupling network that provides a bias path without any connection to ground, thus resulting in a high CMRR. The circuit being passive, it does not limit the differential dc input voltage. Furthermore, differential signals are ac coupled, whereas common-mode voltages are dc coupled, thus allowing the closed-loop control of the dc common mode voltage by means of a driven-right-leg circuit. This makes the circuit compatible with common-mode dc shifting strategies intended for single-supply biopotential amplifiers. The proposed circuit allows the implementation of high-gain biopotential amplifiers with a reduced number of parts, thus resulting in low power consumption. An electrocardiogram amplifier built according to the proposed design achieves a CMRR of 123 dB at 50 Hz.     

Region-based wavelet coding methods for digital mammography

Spatial resolution and contrast sensitivity requirements for some types of medical image techniques, including mammography, delay the implementation of new digital technologies, namely, computer-aided diagnosis, picture archiving and communications systems, or teleradiology. In order to reduce transmission time and storage cost, an efficient data-compression scheme to reduce digital data without significant degradation of medical image quality is needed. In this study, we have applied two region-based compression methods to digital mammograms. In both methods, after segmenting the breast region, a region-based discrete wavelet transform is applied, followed by an object-based extension of the set partitioning in hierarchical trees (OB-SPIHT) coding algorithm in one method, and an object-based extension of the set partitioned embedded block (OB-SPECK) coding algorithm in the other. We have compared these specific implementations against the original SPIHT and the new standard JPEG 2000, both using reversible and irreversible filters, on five digital mammograms compressed at rates ranging from 0.1 to 1.0 bit per pixel (bbp). Distortion was evaluated for all images and compression rates by the peak signal-to-noise ratio. For all images, OB-SPIHT and OB-SPECK performed substantially better than the traditional SPIHT and JPEG 2000, and a slight difference in performance was found between them. A comparison applying SPIHT and the standard JPEG 2000 to the same set of images with the background pixels fixed to zero was also carried out, obtaining similar implementation as region-based methods. For digital mammography, region-based compression methods represent an improvement in compression efficiency from full-image methods, also providing the possibility of encoding multiple regions of interest independently.     

ARP-P4: deep analysis of a hybrid SDN ARP-Path/P4Runtime switch

Telecommunication Systems - The Software-Defined Networking (SDN) architecture decouples the control plane from the data plane, but it does not explicitly state where the control should be located....     

A Privacy-Considerate Framework for Identity Management in Mobile Services

The subscribers’ personal information and services that mobile operators are able to provide to Web developers offer new and exciting possibilities in numerous domains. However, bringing mobile information services to the Web to enable a new generation of mobile Web services presents several research challenges on identity and privacy management. In this paper, we describe a framework for identity management in mobile services that empowers users to govern the use and release of their personal information. Our framework is based on a brokering approach that intermediates between the mobile operator’s information services and the Web service providers. By leveraging on Web services, identity management infrastructure and privacy enhancing technologies, our framework provides an effective, privacy-considerate delivery of services over the mobile Web environment. This paper describes the design principles and architecture of the framework as well as the feasibility, applicability and user-experience evaluation we have carried out.     

Design of Two‐Stage Class AB CMOS Buffers: A Systematic Approach

A systematic approach for the design of two‐stage class AB CMOS unity‐gain buffers is proposed. It is based on the inclusion of a class AB operation to class A Miller amplifier topologies in unity‐gain negative feedback by a simple technique that does not modify quiescent currents, supply requirements, noise performance, or static power. Three design examples are fabricated in a 0.5 µm CMOS process. Measurement results show slew rate improvement factors of approximately 100 for the class AB buffers versus their class A counterparts for the same quiescent power consumption (< 200 µW).     

A Low-Cost and Low-Power Messaging System Based on the LoRa Wireless Technology

Mobile Networks and Applications - In this paper we describe a low-cost and low-power consumption messaging system based on LoRa technology. More that one billion people worldwide cannot access...     

Evidence of Oxygen Ferromagnetism in ZnO Based Materials

Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.     

Analysis and design of punctured rate-1/2 turbo codes exhibiting low error floors

The objective of this paper is two-fold. Initially, we present an analytic technique to rapidly evaluate an approximation to the union bound on the bit error probability of turbo codes. This technique exploits the most significant terms of the union bound, which can be calculated straightforwardly by considering the properties of the constituent convolutional encoders. Subsequently, we use the bound approximation to demonstrate that specific punctured rate-1/2 turbo codes can achieve a lower error floor than that of their rate-1/3 parent codes. In particular, we propose pseudo-random puncturing as a means of improving the bandwidth efficiency of a turbo code and simultaneously lowering its error floor.