Effects of Nodes Geometry and Power Allocation in Space-Time Coded Cooperative Wireless Systems

Cooperative communications are effective in improving the performance and extend the coverage of wireless networks. One issue is to find proper methods to allocate cooperative nodes. In this paper we investigate the effects of relay position and power allocation strategy in cooperative communications employing space-time codes (STCs). We consider non-ideal links between source, relay, and destination enabling the analysis of relay allocation problem based on the performance of each link in realistic scenarios. The frame error rate for various channel conditions, available diversity, relay positions, and transmitted power levels is obtained. Both the situation of balanced and unbalanced transmit power levels for source, relay, and destination are compared. Cooperative pragmatic STCs in block fading channel (BFC) are considered for our analysis. The results provide insight on how to allocate relay nodes based on geometry, link quality, and transmitted power considerations.     

Comparison of energy intake prediction algorithms for systems powered by photovoltaic harvesters

Small size photovoltaic modules can harvest enough energy to power many personal devices and wireless sensor nodes. The prediction of solar energy intake is possible thanks to the periodical availability of the sunlight and its cyclic behavior. Thus, smart and innovative power management strategies can take advantage from intake prediction algorithms to optimize the energy usage by keeping the system in low power state as long as possible. On the other hand, very accurate predictions need time and energy because of complex calculations, thus an algorithm that can provide the optimal trade-off between computational effort and accuracy is a breakthrough for systems with tight power constraints. In this paper we introduce an innovative, efficient and reliable solar prediction algorithm, the weather conditioned moving average (WCMA). The algorithm has been further enhanced to increase performance using a phase displacement regulator (PDR) which reduces the average error to less than 9.2% at a minimum energy cost. The proposed new algorithm compares favorably with several competing approaches.     

Survivable routing in IP-over-WDM networks: An efficient and scalable local search algorithm

In IP-over-WDM networks, a logical IP network is routed on top of a physical optical fiber network. An important challenge here is to make the routing survivable. We call a routing survivable if the connectivity of the logical network is guaranteed in the case of a failure in the physical network. In this paper we describe FastSurv, a local search algorithm for survivable routing. The algorithm works in an iterative manner: after each iteration it learns more about the structure of the logical graph and in the next iteration it uses this information to improve its solution. The algorithm can take link capacity constraints into account and can be extended to deal with multiple simultaneous link failures and node failures. In a large series of tests we compare FastSurv with current state-of-the-art algorithms for this problem. We show that it can provide better solutions in much shorter time, and that it is more scalable with respect to the number of nodes, both in terms of solution quality and run time.     

Metabolic P Systems： A Discrete Model for Biological Dynamics

A recent methodology to model biochem- ical systems is here presented. It is based on a concep- tual framework rooted in membrane computing and de- veloped with concepts typical of discrete dynamical sys- tems. According to our approach, from data observed at suitable macroscopic temporal scales, one can deduce, by means of algebraic and algorithmic procedures, a dis- crete model （called Metabolic P system） which accounts for the experimental data, and opens the possibility to under- stand the systemic logic of the investigated phenomenon. The procedures of such a method have been implemented within a computational platform, a Java software called MetaPlab, processing data and simulating behaviors of metabolic models. In the paper, we briefly describe the theory underlying the modeling of biochemical systems by Metabolic P systems, along with its development stages and the related extensive literature.     

Performance evaluation of an IEEE 802.11g mesh network with multiradio nodes

Wireless mesh networks are usually formed by self‐organized nodes and characterized by high reliability and modularity, low‐cost deployment, and easiness of reconfigurability. In order to improve wireless mesh network performance, several approaches have been recently proposed. Among them, one promising solution seems to be the multiradio interface approach where nodes forming the mesh network are equipped with more than one radio interface. The aim of this paper is to provide an IEEE 802.11 distributed coordination function analytical model to study the behavior of single‐hop multi‐interface mesh networks in which nodes use a uniform random interface selection strategy to identify the radio interface to be used. The accuracy of the proposed analytical approach is validated by comparing analytical predictions with simulation results under actual conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

用于电源测试的精确压控电流阱

为了检测潜在的电源缺陷,必须进行动态和静态测试。这里的简单电流阱可测试低到中功率电源和恒压源。在该应用中,在输入电压范围为0V～5V,电源电压最高为20V时,电流阱可吸收0A～1.5A的电流。该电路的基本部件为一个精密运放IC1,采用Texas Instruments的OPA277。该器件特点为：最大输入偏置电压仅为100μV,最大输入偏置电流为4nA,在-40℃-＋85℃温度范围内温漂较低（图1）。运放IC将其正输入电压与检测电阻RSENSE上的电压进行比较。     

State‐of‐the‐Art Neutral Tint Multichromophoric Polymers for High‐Contrast See‐Through Electrochromic Devices

Two new multichromophoric electrochromic polymers featuring a conjugated EDOT/ProDOT copolymer backbone (PXDOT) and a reversible Weitz‐type redox active small molecule electrochrome (WTE) tethered to the conjugated chain are reported here. The careful design of the WTEs provides a highly reversible redox behavior with a colorless red switching that complements the colorless blue switching of the conjugated backbone. Subtractive color mixing successfully provides high performing solution processable polymeric layers with colorless neutral tint switchable limiting states for application in see‐through electrochromic devices. Design, synthesis, comprehensive chemical and spectroelectrochemical characterization as well as the preparation of a proof‐of‐concept device are discussed.     

Completely automated multiresolution edge snapper--a new technique for an accurate carotid ultrasound IMT measurement: clinical validation and benchmarking on a multi-institutional database

The aim of this paper is to describe a novel and completely automated technique for carotid artery (CA) recognition, far (distal) wall segmentation, and intima-media thickness (IMT) measurement, which is a strong clinical tool for risk assessment for cardiovascular diseases. The architecture of completely automated multiresolution edge snapper (CAMES) consists of the following two stages: 1) automated CA recognition based on a combination of scale-space and statistical classification in a multiresolution framework and 2) automated segmentation of lumen-intima (LI) and media-adventitia (MA) interfaces for the far (distal) wall and IMT measurement. Our database of 365 B-mode longitudinal carotid images is taken from four different institutions covering different ethnic backgrounds. The ground-truth (GT) database was the average manual segmentation from three clinical experts. The mean distance ± standard deviation of CAMES with respect to GT profiles for LI and MA interfaces were 0.081 ± 0.099 and 0.082 ± 0.197 mm, respectively. The IMT measurement error between CAMES and GT was 0.078 ± 0.112 mm. CAMES was benchmarked against a previously developed automated technique based on an integrated approach using feature-based extraction and classifier (CALEX). Although CAMES underestimated the IMT value, it had shown a strong improvement in segmentation errors against CALEX for LI and MA interfaces by 8% and 42%, respectively. The overall IMT measurement bias for CAMES improved by 36% against CALEX. Finally, this paper demonstrated that the figure-of-merit of CAMES was 95.8% compared with 87.4% for CALEX. The combination of multiresolution CA recognition and far-wall segmentation led to an automated, low-complexity, real-time, and accurate technique for carotid IMT measurement. Validation on a multiethnic/multi-institutional data set demonstrated the robustness of the technique, which can constitute a clinically valid IMT measurement for assistance in atherosclerosis disease management.     

Using SPDY to improve Web 2.0 over satellite links

During the last decade, the Web has grown in terms of complexity, while the evolution of the HTTP (Hypertext Transfer Protocol) has not experienced the same trend. Even if HTTP 1.1 adds improvements like persistent connections and request pipelining, they are not decisive, especially in modern mixed wireless/wired networks, often including satellites. The latter play a key role for accessing the Internet everywhere, and they are one of the preferred methods to provide connectivity in rural areas or for disaster relief operations. However, they suffer of high‐latency and packet losses, which degrade the browsing experience. Consequently, the investigation of protocols mitigating the limitations of HTTP, also in challenging scenarios, is crucial both for the industry and the academia. In this perspective, SPDY, which is a protocol optimized for the access to Web 2.0 contents over fixed and mobile devices, could be suitable also for satellite links. Therefore, this paper evaluates its performance when used both in real and emulated satellite scenarios. Results indicate the effectiveness of SPDY if compared with HTTP, but at the price of a more fragile behavior when in the presence of errors. Besides, SPDY can also reduce the transport overhead experienced by middleboxes typically deployed by service providers using satellite links. Copyright © 2016 John Wiley & Sons, Ltd.