Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 5 Articles
CAC (Call Admission Control) plays a significant role in providing QoS (Quality of Service) in mobile wireless networks. In\r\naddition to much research that focuses on modified Mobile IP to get better efficient handover performance, CAC should be\r\nintroduced toMobile IP-based network to guarantee the QoS for users. In this paper, we propose a CAC scheme which incorporates\r\nmultiple traffic types and adjusts the admission threshold dynamically using fuzzy control logic to achieve better usage of resources.\r\nThe method can provide QoS inMobile IPv6 networks with few modifications on MAP (Mobility Anchor Point) functionality and\r\nslight change in BU (Binding Update) message formats. According to the simulation results, the proposed scheme presents good\r\nperformance of voice and video traffic at the expenses of poor performance on data traffic. It is evident that these CAC schemes\r\ncan reduce the probability of the handoff dropping and the cell overload and limit the probability of the new call blocking....
Extensive research addressing IEEE 802.11e enhanced distributed channel access (EDCA) performance analysis, by means of\r\nanalytical models, exist in the literature. Unfortunately, the currently proposed models, even though numerous, do not reach this\r\naccuracy due to the great number of simplifications that have been done. Particularly, none of these models considers the 802.11e\r\ncontention free burst (CFB) mode which allows a given station to transmit a burst of frames without contention during a given\r\ntransmission opportunity limit (TXOPLimit) time interval. Despite its influence on the global performance, TXOPLimit is ignored\r\nin almost all existing models. To fill in this gap, we develop in this paper a new and complete analytical model that (i) reflects the\r\ncorrect functioning of EDCA, (ii) includes all the 802.11e EDCA differentiation parameters, (iii) takes into account all the features\r\nof the protocol, and (iv) can be applied to all network conditions, going from nonsaturation to saturation conditions. Additionally,\r\nthis model is developed in order to be used in admission control procedure, so it was designed to have a low complexity and an\r\nacceptable response time. The proposed model is validated by means of both calculations and extensive simulations....
One of the efficient ways to transmit high data rate is by employing a multiple-input multiple-output (MIMO) transmission. One\r\nof the MIMO schemes, known as spatialmultiplexing (SM), relies on the linear independence data streams from different transmit\r\nantennas to exploit the capacity from the fading channels. Consequently, SM suffers from the effect of spatial correlation which is\r\nthe limiting factor in achieving the capacity benefit that SM can offer. In an attempt to increase the robustness of the SM transmission\r\nin a wide range of correlated channels, the use of dynamic subcarrier allocation (DSA) is investigated. The effective signalto-\r\ninterference-and-noise ratio (SINR) metric is used as the performance metric to determine the subcarrier quality which can\r\nthen be utilised in the allocation. Two novel variants of the subcarrier allocation scheme are proposed. It is shown that the DSASINR\r\napproach improves the BER performance of SM transmission in highly correlated channels environment....
The constraint of a wireless network has motivated many researchers to develop network-aware applications that can dynamically\r\nadjust the users� demand based on network resources. For this to happen, applications need to have some mechanism that can\r\nestimate the network bandwidth by simply adjusting their behavior based on the collected network characteristics information.\r\nIn the past, there have been several proposals that provide passive and active bandwidth estimation approaches for wired and\r\nwireless network. However, little effort has been spent to address the crucial issues of reliability and congestion control especially\r\nin a wireless network environment, which stay as a sticking point for the success of network-aware application. This paper\r\nfocuses on providing accurate, low-intrusiveness, and fast-convergence time bandwidth estimation for network-aware application\r\narchitecture. The experimental results validate the efficiency of the proposed solution in terms of accuracy, intrusiveness, and\r\ntimelines....
This paper proposes a new replica placement algorithm that expands the exhaustive search limit with reasonable calculation time.\r\nIt combines a new type of parallel data-flow processor with an architecture tuned for fast calculation. The replica placement\r\nproblem is to find a replica-server set satisfying service constraints in a content delivery network (CDN). It is derived from the\r\nset cover problem which is known to be NP-hard. It is impractical to use exhaustive search to obtain optimal replica placement in\r\nlarge-scale networks, because calculation time increases with the number of combinations. To reduce calculation time, heuristic\r\nalgorithms have been proposed, but it is known that no heuristic algorithm is assured of finding the optimal solution. The proposed\r\nalgorithm suits parallel processing and pipeline execution and is implemented on DAPDNA-2, a dynamically reconfigurable\r\nprocessor. Experiments show that the proposed algorithm expands the exhaustive search limit by the factor of 18.8 compared\r\nto the conventional algorithm search limit running on a Neumann-type processor....
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