Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
Scalable video coding allows an efficient provision of video services at different quality levels with different energy demands.\r\nAccording to the specific type of service and network scenario, end users and/or operators may decide to choose among different\r\nenergy versus quality combinations. In order to deal with the resulting trade-off, in this paper we analyze the number of video\r\nlayers that are worth to be received taking into account the energy constraints. A single-objective optimization is proposed based\r\non dynamically selecting the number of layers, which is able to minimize the energy consumption with the constraint of a minimal\r\nquality threshold to be reached. However, this approach cannot reflect the fact that the same increment of energy consumption\r\nmay result in different increments of visual quality.Thus, amultiobjective optimization is proposed and a utility function is defined\r\nin order to weight the energy consumption and the visual quality criteria. Finally, since the optimization solving mechanism is\r\ncomputationally expensive to be implemented in mobile devices, a heuristic algorithm is proposed. This way, significant energy\r\nconsumption reduction will be achieved while keeping reasonable quality levels....
Due to the dynamic nature of mobile ad hoc network (MANET), the quality of service (QoS) requires several improvements. The\r\npresent paper comes within the framework of research to optimize QoS in MANET. In this paper, we propose a novel version of\r\nOLSR based on the clustering approach which is inspired from Lin and Chu heuristic and adapted to be implemented in OLSR.\r\nWe studied its stability and we compared its performances to those of standard OLSR.The metrics we used in evaluating network\r\nperformances were average end-to-end delay, control routing overhead, and packet delivery ratio. Experimental results show that\r\nour alternative significantly reduces the traffic reserved to monitoring the network, which positively influences other performances\r\nsuch as throughput, delay, and loss....
Multimedia sensor networks for real-time applications have strict constraints on delay, packet loss, and energy consumption\r\nrequirements. For example, video streaming in a disaster-management scenario requires careful handling to ensure that the endto-\r\nend delay is within the acceptable range and the video is received properly without any distortion. The failure to transmit a\r\nvideo streameffectively occurs formany reasons, including sensor function limitations, excessive power consumption, and a lack of\r\nrouting reliability.We propose a novel mathematical model for quality of service (QoS) route determination that enables a sensor to\r\ndetermine the optimal path for minimising resource use while satisfying the required QoS constraints. The proposed mathematical\r\nmodel uses the Lagrangian relaxation mixed integer programming technique to define critical parameters and appropriate objective\r\nfunctions for controlling the adaptive QoS constrained route discovery process. Performance trade-offs between QoS requirements\r\nand energy efficiency were simulated using the LINGO mathematical programming language.The proposed approach significantly\r\nimproves the network lifetime, while reducing energy consumption and decreasing average end-to-end delays within the sensor\r\nnetwork via optimised resource sharing in intermediate nodes compared with existing routing algorithms....
The high bandwidth demand of Internet applications has recently driven the need of increasing the residential download speed.\r\nA practical solution to the problem is to aggregate the bandwidth of 802.11 access points (APs) backhauls in range. Since 802.11\r\ndevices are usually single radio, the communication to APs on different radio channels requires a time-division multiple access\r\n(TDMA) policy at the client station. With an in-depth experimental analysis and a customized 802.11 driver, in this paper, we\r\nshow that the usage of multi-AP TDMA policy may cause degradation of the TCP throughput and an underutilization of the AP\r\nbackhauls. We then introduce a simple analytical model that accurately predicts the TCP round-trip time (RTT) with a multi-AP\r\nTDMA policy and propose a resource allocation algorithm to reduce the observed TCP RTT with a very low computational cost.\r\nOur proposed scheme runs locally at the client station and improves the aggregate throughput up to 1.5 times compared to stateof-\r\nthe-art allocations.We finally show that the throughput achieved by our algorithm is very close to the theoretical upper bound\r\nin key simulation scenarios....
Stringent QoS requirements of video streaming are not addressed by the delay characteristics of highly dynamic peer-to-peer (P2P)\r\nnetworks. To solve this problem, a novel locality-aware method for choosing optimal neighbors in live streaming multicast P2P\r\noverlays is presented in this paper. To create the appropriate multicast tree topology, a round-trip-time (RTT) value is used as a\r\nparameter distinguishing peers capabilities.Themulticast tree construction is based on theHuffman source coding algorithm. First,\r\na centrally managed version is presented, and then an effective use of a distributed paradigm is shown. Performance evaluation\r\nresults prove that the proposed approach considerably improves the overlay efficiency from the viewpoint of end-users and\r\ncontent providers.Moreover, the proposed technique ensures a high level of resilience against gateway-link failures and adaptively\r\nreorganizes the overlay topology in case of dynamic, transient network fluctuations....
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