Topic
Greedy source
About: Greedy source is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 42 citations.
Papers
1 Jan 2010
TL;DR: In this paper, the authors investigate the stability of CSMA-based wireless mesh networks, where a network is said to be stable if and only if the queue of each relay node remains (almost surely) finite.
Abstract: We investigate, both theoretically and experimentally, the stability of CSMA-based wireless mesh networks, where a network is said to be stable if and only if the queue of each relay node remains (almost surely) finite. We identify two key factors that impact stability: the network size and the so-called "stealing effect", a consequence of the hidden node problem and non-zero transmission delays. We consider the case of a greedy source and prove, by using Foster's theorem, that 3-hop networks are stable, but only if the stealing effect is accounted for. We also prove that 4-hop networks are, on the contrary, always unstable (even with the stealing effect) and show by simulations that instability extends to more complex linear and non-linear topologies. To tackle this instability problem, we propose and evaluate a novel, distributed flow-control mechanism, called EZ-flow. EZ-flow is fully compatible with the IEEE 802.11 standard (i.e., it does not modify headers in packets), can be implemented using off-the-shelf hardware, and does not entail any communication overhead. EZ-flow operates by adapting the minimum congestion window parameter at each relay node, based on an estimation of the buffer occupancy at its successor node in the mesh. We show how such an estimation can be conducted passively by taking advantage of the broadcast nature of the wireless channel. Real experiments, run on a 9-node testbed deployed over 4 different buildings, show that EZ-flow effectively smoothes traffic and improves delay, throughput, and fairness performance.
18 citations
22 Jun 2009
TL;DR: This work considers the case of a greedy source and proves, by using Foster's theorem, that 3-hop networks are stable, but only if the stealing effect is accounted for, and devise a stabilization strategy that throttles the source and prove that there exists a finite, non-zero rate at which the source can transmit while keeping the system stable.
Abstract: We investigate both theoretically and experimentally the stability of CSMA-based wireless mesh networks, where a network is said to be stable if and only if the queue of each relay node remains (almost surely) finite. We identify two key factors that impact stability: the network size and the so-called "stealing effect", a consequence of the hidden node problem and non-zero propagation delays. We consider the case of a greedy source and prove, by using Foster's theorem, that 3-hop networks are stable, but only if the stealing effect is accounted for. On the other hand, we prove that 4-hop networks are always unstable (even with the stealing effect) and show by simulations that instability extends to more complex linear and non-linear topologies. We devise a stabilization strategy that throttles the source and prove that there exists a finite, non-zero rate at which the source can transmit while keeping the system stable. We run real experiments on a testbed composed of IEEE 802.11 nodes, which show the contrasting behavior of 3-hop and 4-hop networks and the effectiveness of our stabilization strategy.
17 citations
TL;DR: It is shown that these objectives may not be achieved simultaneously unless both network and source coding considerations are taken into account, and that, given a rate constraint, a greedy source coding strategy will reduce the potential for statistical multiplexing gain in the network.
Abstract: In this paper, we study the rate constraints required for variable rate video transmission over ATM networks. Our objective is to achieve both good source quality and efficient network utilization. We show that these objectives may not be achieved simultaneously unless both network and source coding considerations are taken into account. In particular, we show that, given a rate constraint, a greedy source coding strategy will reduce the potential for statistical multiplexing gain in the network. We propose two alternative methods to achieve our goals. The fil st method requires non-greedy source coding techniques, implementable through I ate control, such that video encoders will only use the bit rate needed to achieve a certain, nearly constant quality level. As a consequence, low activity scenes will use a fraction of the maximum allowable bit rate. The second method calls for increasing the number of rate constraints imposed on each connection so that the amount of bandwidth used in the worst case (ie by greedy coders) is limited. Experimental results for a medium length (5 min) video sequence are given.
7 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2010 | 1 |
| 2009 | 1 |
| 1995 | 1 |