Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 5 Articles
We investigate into the potentiality of an enhanced Power and Location-based Vertical Handover (PLB-VHO) approach, based\r\non a combination of physical parameters (i.e., location and power attenuation information), for mobile-controlled connectivity\r\nacrossUMTS and WLAN networks.We show that the location information in amultiparameter vertical handover can significantly\r\nenhance communication performance. In the presented approach a power attenuation map for the visited area is built and\r\nkept updated by exploiting the information sharing of power measurements with other cooperating mobile devices inside the\r\nvisited networks. Such information is then used for connectivity switching in handover decisions. The analytical model for the\r\nproposed technique is first presented and then compared with a traditional Power-Based approach and a simplified Location-Based\r\ntechnique. Simulation results showthe effectiveness of PLB-VHOapproach, in terms of (i) network performance optimization and\r\n(ii) limitation of unnecessary handovers (i.e., mitigation of ping-pong effect)....
We study the important problem of resource allocation for the downlink of Multiple-Input Multiple output (MIMO) Multicast\r\nWireless Systems operating over frequency-selective channels and we propose a low-complexity but efficient resource allocation\r\nalgorithm for MIMO-enabled OFDMA systems. The proposed solution guarantees a minimum spectrum share for each user\r\nwhile also takes advantage of the multicast transmission mode. The presence of multiple antennas in both transmitter and receiver\r\noffers spatial diversity to the system along with the frequency diversity added by the OFDMA access scheme. The computational\r\ncomplexity is reduced from exponential to linear and validation of the proposed solution is achieved through various simulation\r\nscenarios in comparison with other multicast and unicast reference schemes used in MIMO-OFDMA systems. Numerical results\r\nand complexity analysis demonstrate the feasibility of the proposed algorithm....
We propose an idle probability-based broadcasting method, iPro, which employs an adaptive probabilistic mechanism to improve\r\nperformance of data broadcasting over dense wireless ad hoc networks. In multisource one-hop broadcast scenarios, the modeling\r\nand simulation results of the proposed iPro are shown to significantly outperform the standard IEEE 802.11 under saturated\r\ncondition. Moreover, the results also show that without estimating the number of competing nodes and changing the contention\r\nwindow size, the performance of the proposed iPro can still approach the theoretical bound. We further apply iPro to multihop\r\nbroadcasting scenarios, and the experiment results show that within the same elapsed time after the broadcasting, the proposed\r\niPro has significantly higher Packet-Delivery Ratios (PDR) than traditional methods....
Internet television (IPTV) is rapidly gaining popularity and is being widely deployed in content delivery networks on the Internet.\r\nIn order to proactively deliver optimum user quality of experience (QoE) for IPTV, service providers need to identify network\r\nbottlenecks in real time. In this paper, we develop psycho-acoustic-visual models that can predict user QoE of multimedia\r\napplications in real time based on online network status measurements. Our models are neural network based and cater to\r\nmulti-resolution IPTV applications that include QCIF, QVGA, SD, and HD resolutions encoded using popular audio and video\r\ncodec combinations. On the network side, our models account for jitter and loss levels, as well as router queuing disciplines:\r\npacket-ordered and time-ordered FIFO.We evaluate the performance of our multi-resolution multimedia QoE models in terms of\r\nprediction characteristics, accuracy, speed, and consistency. Our evaluation results demonstrate that the models are pertinent for\r\nreal-time QoE monitoring and resource adaptation in IPTV content delivery networks....
This paper is focused on the problem of optimizing the aggregate throughput of the distributed coordination function (DCF)\r\nemploying the basic access mechanism at the data link layer of IEEE 802.11 protocols. We consider general operating conditions\r\naccounting for both nonsaturated and saturated traffic in the presence of transmission channel errors, as exemplified by the packet\r\nerror rate Pe. The main clue of this work stems from the relation that links the aggregate throughput of the network to the packet\r\nrate ? of the contending stations. In particular, we show that the aggregate throughput S(?) presents two clearly distinct operating\r\nregions that depend on the actual value of the packet rate ? with respect to a critical value ?c , theoretically derived in this work. The\r\nbehavior of S(?) paves the way to a cross-layer optimization algorithm, which proved to be effective for maximizing the aggregate\r\nthroughput in a variety of network operating conditions. A nice consequence of the proposed optimization framework relies on\r\nthe fact that the aggregate throughput can be predicted quite accurately with a simple, yet effective, closed-formexpression. Finally,\r\ntheoretical and simulation results are presented in order to unveil, as well as verify, the key ideas....
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