One of the most widely considered cache replacement policies is Least Recently Used (LRU) based on which many other policies have been developed. LRU has been studied analytically in the literature under the assumption that the object requests are independent. However, such an assumption does not seem to be in agreement with recent studies of Web-traces, which indicate the existence of short term correlations among the requests. This paper introduces an approximate analysis that fairly accurately predicts the hit ratio of the LRU policy in the case of short term correlations. The approximation approach is based on the relation between the working set model and LRU, while the request generation process is assumed to follow a recently proposed model for Web-traces, which captures short term correlations among the requests. The accuracy of the introduced approximate analysis is validated for synthetic as well as real Web-traces.
Abstract-In this paper, a Delay Tolerant Network environment is considered where the source is in full control of the two-hop spreading mechanism by setting key parameters such as the number of copies allowed to be spread in the network and the delay bound of the messages. The analysis allows for a differentiation between the source of the message and the intermediate nodes (in terms of e.g. transmission power or speed). Analytical expressions for the cumulative distribution function (cdf ) of the delivery delay and the induced overhead are extracted, taking into account the fact that the source node may continue spreading copies after the message delivery. In addition, a fairly accurate approximate expression for the cdf of the delivery delay is also derived and validated through simulations.
BroadWay (IST-2001-32686) is an Information Society Technologies project. It is a three-year project, which started in 2002, and it is partly funded by the Commission of the European Community. The partners involved in the project are the Motorola Labs (France), TNO-FEL (Netherlands), Intracom and the National & Kapodistrian University of Athens (Greece), IMST, IRK and Dresden University of Technology (Germany) and FARRAN (Ireland).BroadWay aims to develop a tightly integrated platform for hot spots supporting private (e-home, entertainment, business) and public (fast outdoor downloading) applications. This platform will be able to cope with very dense user environments satisfying the user expectations in terms of the available throughput. BroadWay objectives include the definition, development and demonstration of the components of a hybrid dual frequency system based on HIPERLAN/2 OFDM high spectrum efficiency technology at 5 GHz and an innovative fully ad-hoc extension at 60 GHz, named HIPERSPOT. The HIPERSPOT system architecture will be based on hardware extensions of HIPERLAN/2 in order to ensure easy reconfigurability and allow for backward compatibility with the 5 GHz technology. It will support two compatible classes of mobile terminals: one of lower cost that will target the same transmission speed as HIPERLAN/2 (25 Mbps or even less data rate) and one providing a significantly higher data rate (more than 100 Mbps) than the maximum possible in HIPERLAN/2 by exploiting the larger bandwidth available at 60 GHz. HIPERSPOT will be equipped with a novel modified multi-carrier transmission scheme enhancing the robustness of transmissions at 60 GHz. Main goals of BroadWay are to offload the 5 GHz radio band in dense deployment areas, to exactly focus radio beams and to allow for self-organizing autonomous operation at the new frequency.BroadWay is obviously part of the 4G scenario, as it complements the wide area infrastructure by providing a new hybrid air interface technology working at 5 GHz and at 60 GHz. This air interface is expected to be particularly innovative as it addresses the new concept of convergence between wireless local area network and wireless personal area network systems. The concept of BroadWay extends and complements existing 5 GHz broadband WLAN systems into the 60 GHz range allowing for terminal mobility while providing much higher capacity (achieving data rates exceeding 100 Mbps) and increased
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