QoS provision in wireless access networks: a routing perspective considering mobility

Future wireless communications are expected to provide mobile users access to the desired service with the appropriate quality at any place. The essential elements for assembling such a vision are mobility, quality of service (QoS) provision and scalability, which are expected to be merged into the design process of wireless access networks. Internet mobility support is currently entering a mature phase in which scalable solutions provide low loss or even seamless handovers in cellular and heterogeneous mobile environments. Wireless and mobile QoS architectures extend the equivalent Internet approaches in order to accommodate the requirements associated with the presence of wireless links and mobility. Nevertheless, none of the popular mobility proposals combined with wireless and mobile QoS architectures encounter QoS in the routing function, leaving the QoS provision underutilized. QoS routing (QoSR) complements existing QoS architectures, enhancing application performance especially in the case of congestion, while providing efficient resource management. However, QoSR was originally designed for fixed IP networks without taking mobility into account. This paper investigates the interaction of QoSR in wireless access networks, identifying key points for the efficient cooperation with mobility and existing QoS architectures. Copyright © 2009 John Wiley & Sons, Ltd.     

Error propagation analysis using FPGA-based SEU-fault injection

Error propagation analysis is one of the main objectives of fault injection experiments. This analysis helps designers to detect design mistakes and to provide effective mechanisms for fault tolerant systems. However, error propagation analysis requires that the chosen fault injection technique provides a high degree of observability (i.e., the ability to observe the internal values and events of a circuit after a fault is injected). Simulation-based fault injection provides a high observability adequate for error propagation analysis. However, the performance of the simulation-based technique is inadequate to handle today’s hardware complexity. As an alternative, FPGA-based fault injection can be used to accelerate the fault injection experiments, but the communication time needed for observing the circuit behavior from outside of the FPGA imposes severe limitations on the observability. In this paper, an observation technique for FPGA-based fault injection is proposed which significantly reduces the communication time as compared with previous scan-based observation techniques. Furthermore, this paper describes a SEU-fault injection technique based on a chain of parallel registers which reduces the time needed for injecting SEU faults as compared to the previous scan-based fault-injection techniques. As a case study, a 32-bit pipelined processor has been used in the fault injection experiments. The experimental results show that when a high degree of observability is required (e.g., error propagation analysis), the proposed fault injection technique is over 1166 times faster than simulation-based fault injection, whereas the traditional scan-based technique can achieve only a speedup of about 2–3 – which means that the proposed technique is about 500 times faster than the traditional scan-based technique. Such results are supported by theoretical performance analysis. This speed increase has been achieved without excessive increase in FPGA resource overhead, for example, the FPGA overhead of the proposed technique is only 2  3% higher than that of the traditional scan-based technique.     

Telesurgery QoS improvement over SDN based on a Type‐2 fuzzy system and enhanced cuckoo optimization algorithm

Telemedicine is a new area based on the information and communication technology for collecting, storing, organizing, retrieving and exchanging medical information. One of the most important applications of telemedicine is indeed telesurgery in which an efficient telecommunication infrastructure between the surgery room and remote surgeons need to be established. One of the most important issues to be tackled in telesurgery is to find favorable links for routing as well as providing high Quality of Service (QoS). In this paper, an efficient model based on the hybridization of Type‐2 Fuzzy System (T2FS) and Cuckoo Optimization Algorithm (COA) over the Software Defined Networks (SDN) is proposed in order to achieve optimal and reliable routes for telesurgery application. Using T2FS, the fitness of the links is determined; then, a COA is conducted over the Constraint Shortest Path (CSP) problem to find the best routes. Delay is considered as a CSP problem which is satisfied by trying to find the paths with minimum cost. Due to the NP‐completeness of the CSP problem, an Enhanced COA (so‐called E‐COA) is proposed and utilized as a metaheuristic solver. To the best of our knowledge, this paper is the first SDN‐based communication model that applies both T2FS and E‐COA for assigning proper costs to the network's links, and solves the consequence CSP problem according to the QoS requirement for telesurgery. The model also recognizes and preserves the second‐best routes in order to keep the reliability for such a critical application. In addition to the simulations, the performance evaluation is also conducted on a real experimental scenario. Many comparisons are carried out between the proposed model and other conventional methods, and the evaluation study shows the superiority of the proposed model on all the three QoS‐related metrics, i.e. average end‐to‐end delay, packet loss ratio and PSNR.     

Dependability analysis for characterizing Google cluster reliability

Cloud solutions are emerging as a new suitable way of transforming traditional IT data centers to highly available and reliable computing resources for hosting critical applications and data. However, software and hardware failures are a common problem in cloud datacenters that can lead to harmful damages. In this paper, we analyze the physical server failures in the Google cloud datacenter. We study the Google cluster properties to investigate the relationship among physical servers' failure rate and jobs failure events. The failure rate of Google cluster executed jobs and servers is taken into consideration during a 29‐day period. We present a reliability model for Google cluster physical machines using the continuous time Markov chains according to this observation. We attempt to analyze the obtained model through SHARPE software packages to improve the understanding of failure events in the Google cloud cluster. We also explore the cluster availability based on parameters like steady‐state availability, steady‐state unavailability, mean time to failure, and mean time to repair in the Google cluster.     

CCGA packages for space applications

Commercial-off-the-shelf (COTS) area array packaging technologies in high reliability versions are now being considered for applications, including use in a number of NASA electronic systems being utilized for both the Space Shuttle and Mars Rover missions. Indeed, recently a ceramic package version specifically tailored for high reliability applications was used to provide the processing power required for the Spirit and Opportunity Mars Rovers built by NASA-JPL. Both Rovers successfully completed their 3-months mission requirements and continued exploring the Martian surface for many more moths, providing amazing new information on previous environmental conditions of Mars and strong evidence that water exists on Mars.Understanding process, reliability, and quality assurance (QA) indicators for reliability are important for low risk insertion of these newly available packages in high reliability applications. In a previous investigation, thermal cycle test results for a non-functional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version, both having 560 I/Os, were gathered and are presented here. Test results included environmental data for three different thermal cycle regimes (−55/125 °C, −55/100 °C, and −50/75 °C). Detailed information on these—especially failure type for assemblies with high and low solder volumes—are presented. The thermal cycle test procedure followed those recommended by IPC-9701 for tin–lead solder joint assemblies. Its revision A covers guideline thermal cycle requirements for Pb-free solder joints. Key points on this specification are also discussed.In a recent investigation a fully populated CCGA with 717 I/Os was considered for assembly reliability evaluation. The functional package is a field-programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for assemblies of this and its plastic package version with 728 I/Os, both of which were exposed to four different cycle regimes. Two of these cycle profiles are specified by IPC-9701A for tin–lead, namely, −55 to 100 °C and −55 to 125 °C. One is a cycle profile specified by Mil-Std-883, namely, −65/150 °C, generally used for ceramic hybrid packages screening and qualification. The last cycle is in the range of −120 to 85 °C, a representative of electronic systems directly exposed to the Martian environment without use in a thermal control enclosure. Per IPC-9701A, test vehicles were built using daisy chain packages and were continuously monitored and/or manually checked for opens at intervals. The effects of many process and assembly variables—including corner staking commonly used for improving resistance to mechanical loading such as drop and vibration loads—were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples of these are presented along with cross-sectional photomicrographs at higher magnification taken by scanning electron microscopy (SEM) to determine crack propagation and failure analyses for packages.     

An Intra-domain Mobility Handling Scheme Across All-IP Wireless Networks

The rapid growth of wireless network technology such as HSDPA and WiMAX, has lead to greater demand for access to Internet via mobile hosts. Supporting mobile connection with fast and smooth roaming across heterogeneous wireless technologies has been an important challenge over past years. In this paper, a novel multilayer scheme for QoS-aware intra-domain mobility management is proposed. The mobility support capability is embedded in key components for the domain access network, namely, the Paging Access Routers and the Mobility-support Anchor Servers (MASs). The MASs are organized in three layers; starting from the top layer Superior-MASs, Middle-MASs and Inferior-MASs, respectively. The proposed scheme identified mobility support functionality, includes intra-domain anchor specification, route optimization algorithm, intra/inter-anchor mobility support, paging and authentication management. Simulation results of the proposed scheme show fair performance especially in the presence of QoS sensitive services.     

Assurance of energy efficiency and data security for ECG transmission in BASNs

With the technological advancement in body area sensor networks (BASNs), low cost high quality electrocardiographic (ECG) diagnosis systems have become important equipment for healthcare service providers. However, energy consumption and data security with ECG systems in BASNs are still two major challenges to tackle. In this study, we investigate the properties of compressed ECG data for energy saving as an effort to devise a selective encryption mechanism and a two-rate unequal error protection (UEP) scheme. The proposed selective encryption mechanism provides a simple and yet effective security solution for an ECG sensor-based communication platform, where only one percent of data is encrypted without compromising ECG data security. This part of the encrypted data is essential to ECG data quality due to its unequally important contribution to distortion reduction. The two-rate UEP scheme achieves a significant additional energy saving due to its unequal investment of communication energy to the outcomes of the selective encryption, and thus, it maintains a high ECG data transmission quality. Our results show the improvements in communication energy saving of about 40%, and demonstrate a higher transmission quality and security measured in terms of wavelet-based weighted percent root-mean-squared difference.     

Fusion of magnetometer and gradiometer sensors of MEG in the presence of multiplicative error

Novel neuroimaging techniques have provided unprecedented information on the structure and function of the living human brain. Multimodal fusion of data from different sensors promises to radically improve this understanding, yet optimal methods have not been developed. Here, we demonstrate a novel method for combining multichannel signals. We show how this method can be used to fuse signals from the magnetometer and gradiometer sensors used in magnetoencephalography (MEG), and through extensive experiments using simulation, head phantom and real MEG data, show that it is both robust and accurate. This new approach works by assuming that the lead fields have multiplicative error. The criterion to estimate the error is given within a spatial filter framework such that the estimated power is minimized in the worst case scenario. The method is compared to, and found better than, existing approaches. The closed-form solution and the conditions under which the multiplicative error can be optimally estimated are provided. This novel approach can also be employed for multimodal fusion of other multichannel signals such as MEG and EEG. Although the multiplicative error is estimated based on beamforming, other methods for source analysis can equally be used after the lead-field modification.