A Cache Management Strategy to Replace Wear Leveling Techniques for Embedded Flash Memory

Prices of NAND flash memories are falling drastically due to market growth and fabrication process mastering while research efforts from a technological point of view in terms of endurance and density are very active. NAND flash memories are becoming the most important storage media in mobile computing and tend to be less confined to this area. The major constraint of such a technology is the limited number of possible erase operations per block which tend to quickly provoke memory wear out. To cope with this issue, state-of-the-art solutions implement wear leveling policies to level the wear out of the memory and so increase its lifetime. These policies are integrated into the Flash Translation Layer (FTL) and greatly contribute in decreasing the write performance. In this paper, we propose to reduce the flash memory wear out problem and improve its performance by absorbing the erase operations throughout a dual cache system replacing FTL wear leveling and garbage collection services. We justify this idea by proposing a first performance evaluation of an exclusively cache based system for embedded flash memories. Unlike wear leveling schemes, the proposed cache solution reduces the total number of erase operations reported on the media by absorbing them in the cache for workloads expressing a minimal global sequential rate.Comment: Ce papier a obtenu le "Best Paper Award" dans le "Computer System track" nombre de page: 8; International Symposium on Performance Evaluation of Computer & Telecommunication Systems, La Haye : Netherlands (2011

Link level modelling techniques for analysing the configuration of link adaptation algorithms in mobile radio networks

The operation of Link Adaptation algorithms is based on channel quality estimates. It is therefore important to analyse the performance of such algorithms with link level models that properly capture the channel conditions and dynamics. Previous research [1] concluded that the use of simple link level models does not give an accurate prediction of the estimated performance of Link Adaptation algorithms. Following this previous work, this paper shows that the link level model considered for the study of Link Adaptation algorithms can also influence the decisions regarding the optimum configuration of the algorithm

Enhancing the water point mapping: a WASH approach

Strategic planning and appropriate development and management of water and sanitation services can be strongly supported by accurate and accessible data. If adequately exploited, these data might assist water managers with performance monitoring, benchmarking comparisons, policy progress evaluation, resources allocation, and decision making. A variety of tools and techniques are in place to collect such information. However, some methodological weaknesses arise when developing an instrument for routine data collection, particularly at local level: (i) comparability problems due to heterogeneity of data and sector-re lated indicators, (ii) in adequate combination of different information sources, and (iii) statistical validity of collected data. The purpose of this study is to adopt an integrated water, sanitation and hygiene (WASH) approach for data collection at community level in rural low income settings, as an attempt to overcome previous shortcomings. The survey design takes the Water Point Mapping (WPM) as a starting point to record all available water sources at a particular location, and this information is then linked to data provided from a household-based survey. In order to demonstrate the applicability of the method, a case study is presented at Tiraque Valley (Cochabamba, Bolivia).Peer ReviewedPostprint (published version

Secure data sharing and processing in heterogeneous clouds

The extensive cloud adoption among the European Public Sector Players empowered them to own and operate a range of cloud infrastructures. These deployments vary both in the size and capabilities, as well as in the range of employed technologies and processes. The public sector, however, lacks the necessary technology to enable effective, interoperable and secure integration of a multitude of its computing clouds and services. In this work we focus on the federation of private clouds and the approaches that enable secure data sharing and processing among the collaborating infrastructures and services of public entities. We investigate the aspects of access control, data and security policy languages, as well as cryptographic approaches that enable fine-grained security and data processing in semi-trusted environments. We identify the main challenges and frame the future work that serve as an enabler of interoperability among heterogeneous infrastructures and services. Our goal is to enable both security and legal conformance as well as to facilitate transparency, privacy and effectivity of private cloud federations for the public sector needs. © 2015 The Authors

HILT : High-Level Thesaurus Project. Phase IV and Embedding Project Extension : Final Report

Ensuring that Higher Education (HE) and Further Education (FE) users of the JISC IE can find appropriate learning, research and information resources by subject search and browse in an environment where most national and institutional service providers - usually for very good local reasons - use different subject schemes to describe their resources is a major challenge facing the JISC domain (and, indeed, other domains beyond JISC). Encouraging the use of standard terminologies in some services (institutional repositories, for example) is a related challenge. Under the auspices of the HILT project, JISC has been investigating mechanisms to assist the community with this problem through a JISC Shared Infrastructure Service that would help optimise the value obtained from expenditure on content and services by facilitating subject-search-based resource sharing to benefit users in the learning and research communities. The project has been through a number of phases, with work from earlier phases reported, both in published work elsewhere, and in project reports (see the project website: http://hilt.cdlr.strath.ac.uk/). HILT Phase IV had two elements - the core project, whose focus was 'to research, investigate and develop pilot solutions for problems pertaining to cross-searching multi-subject scheme information environments, as well as providing a variety of other terminological searching aids', and a short extension to encompass the pilot embedding of routines to interact with HILT M2M services in the user interfaces of various information services serving the JISC community. Both elements contributed to the developments summarised in this report