Δομή λεξικού για ασύρματα δίκτυα

Η κατανάλωση ενέργειας και η αποδοτηκότητα πρόσβασης είναι δύο βασικοί στόχοι και ανταγωνιστικοί στην ασύρματη εκπομπή δεδομένων. Για να αντιμετωπιστεί το ενεργειακό πρόβλημα στην ακολουθιακή αναζήτηση μαζί με τα δεδομένα έχουν προστεθεί δείκτες ( index ). Στην εργασία αυτή προτείνουμε ένα παραμετροποιήσημο αλγόριθμο εκπομπής δεδομένων τον Interpolation Index. Ο αλγόριθμος έχει δυνατότητα να βελτιστοποιήσει το χρόνο αναζήτησης κρατώντας σταθερό τον χρόνο συντονισμού (tuning time ) και αντίστροφα

An Efficient interaction framework for mobile web services

Having the latest technological devices is becoming more of a necessity these days rather than a luxury as it was only a decade ago. Among these advancements, the smart phone has grown in popularity significantly. This is due to a variety of reasons but it would have to be said that the access to mobile internet service it provides is a strong motivator for acquiring one. As might be expected the increased number of smart phone users requesting information from the internet has resulted in times when the average access time (the time a user must wait to download his/her requested service) is quite high. In research the use of the wireless carrier\u27s broadcast channels to transmit mobile web services has proven to be an economical way to handle the increased volume of users. However, having not been designed for this purpose, the usual configuration of the broadcast channels fails to take into account the characteristics of today\u27s devices and those of mobile web services. Therefore, this thesis will outline the formulation of an interaction framework that provides an innovative channel design and allocation approach for delivering mobile web services. This architecture will incorporate current usage data (i.e., popularity over specified time period) and the exact dimensions of each mobile web service to more efficiently allocate them, thus resulting in lower average access time

GreenDelivery: Proactive Content Caching and Push with Energy-Harvesting-based Small Cells

The explosive growth of mobile multimedia traffic calls for scalable wireless access with high quality of service and low energy cost. Motivated by the emerging energy harvesting communications, and the trend of caching multimedia contents at the access edge and user terminals, we propose a paradigm-shift framework, namely GreenDelivery, enabling efficient content delivery with energy harvesting based small cells. To resolve the two-dimensional randomness of energy harvesting and content request arrivals, proactive caching and push are jointly optimized, with respect to the content popularity distribution and battery states. We thus develop a novel way of understanding the interplay between content and energy over time and space. Case studies are provided to show the substantial reduction of macro BS activities, and thus the related energy consumption from the power grid is reduced. Research issues of the proposed GreenDelivery framework are also discussed.Comment: 15 pages, 5 figures, accepted by IEEE Communications Magazin

Energy Efficient Varying Fanout Indexing Technique for Skewed Access Patterns in the Wireless Mobile Environments

As we know, due to limited battery power, the most important issue in mobile computing is energy saving, which can be achieved through indexed data organization to broadcast data over wireless channels to a large no of mobile clients. In this paper, we explore the balanced and imbalanced index tree with varying fanout over skewed data. We purpose a varying fanout indexing technique with replication for data broadcast with skewed access pattern over a single wireless communication channel. We also show that replication can be performed at any level in varying fanout index tree, which increases the length of the overall broadcast cycle but reduces the directory miss. We compared our technique with the conventional as well as existing techniques. The performance results suggests the superiority of this technique over another replicated index technique i.e., fixed fanout index in all aspects. Our index technique also ensures correctness of results when larger size of broadcast file is used. From the performance analysis, the proposed indexing technique outperforms fixed fanout index technique

Organization and Strategy of Farmer Specialized Cooperatives in China

A description and analysis of China's Farmer Specialized Cooperatives is presented. Data is presented regarding the historical development of farmer cooperatives in China, the membership composition of a sample of 66 farmer cooperatives in the Zhejiang province, and the various attributes (governance, quality control system, and strategy) of a watermelon cooperative in this province. Many cooperatives are being transformed in organizations with a market orientation. These cooperatives exhibit substantial heterogeneity, in terms of farmers being member and skewness in the distribution of control rights. Human asset specificity in terms of establishing and maintaining relations and access to markets seems to be more important than physical asset specificity in accounting for governance structure choice in the current institutional setting.Farmer Cooperative, China, Governance Structure, Business Strategy, Agribusiness, Q13,

The data cyclotron query processing scheme

Distributed database systems exploit static workload characteristics to steer data fragmentation and data allocation schemes. However, the grand challenge of distributed query processing is to come up with a self-organizing architecture, which exploits all resources to manage the hot data set, minimize query response time, and maximize throughput without global co-ordination. In this paper, we introduce the Data Cyclotron architecture which addresses the challenges using turbulent data movement through a storage ring built from distributed main memory capitalizing modern remote-DMA facilities. Queries assigned to individual nodes interact with the Data Cyclotron by picking up data fragments continuously flowing around, i.e., the hot set. Each data fragment carries a level of interest (LOI) metric, which represents the cumulative query interest as the fragment passes around the ring multiple times. A fragment with a LOI below a given threshold, inversely proportional to the ring load, is pulled o

Design And Analysis Of Scalable Video Streaming Systems

Despite the advancement in multimedia streaming technology, many multimedia applications are still face major challenges, including provision of Quality-of-Service (QoS), system scalability, limited resources, and cost. In this dissertation, we develop and analyze a new set of metrics based on two particular video streaming systems, namely: (1) Video-on-Demand (VOD) with video advertisements system and (2) Automated Video Surveillance System (AVS). We address the main issues in the design of commercial VOD systems: scalability and support of video advertisements. We develop a scalable delivery framework for streaming media content with video advertisements. The delivery framework combines the benefits of stream merging and periodic broadcasting. In addition, we propose new scheduling policies that are well-suited for the proposed delivery framework. We also propose a new prediction scheme of the ad viewing times, called Assign Closest Ad Completion Time (ACA). Moreover, we propose an enhanced business model, in which the revenue generated from advertisements is used to subsidize the price. Additionally, we investigate the support of targeted advertisements, whereby clients receive ads that are well-suited for their interests and needs. Furthermore, we provide the clients with the ability to select from multiple price options, each with an associate expected number of viewed ads. We provide detailed analysis of the proposed VOD system, considering realistic workload and a wide range of design parameters. In the second system, Automated Video Surveillance (AVS), we consider the system design for optimizing the subjects recognition probabilities. We focus on the management and the control of various Pan, Tilt, Zoom (PTZ) video cameras. In particular, we develop a camera management solution that provides the best tradeoff between the subject recognition probability and time complexity. We consider both subject grouping and clustering mechanisms. In subject grouping, we propose the Grid Based Grouping (GBG) and the Elevator Based P lanning (EBP) algorithms. In the clustering approach, we propose the (GBG) with Clustering (GBGC) and the EBP with Clustering (EBPC) algorithms. We characterize the impact of various factors on recognition probability. These factors include resolution, pose and zoom-distance noise. We provide detailed analysis of the camera management solution, considering realistic workload and system design parameters