152 research outputs found
Wireless Broadcast with Network Coding in Mobile Ad-Hoc Networks: DRAGONCAST
Network coding is a recently proposed method for transmitting data, which has
been shown to have potential to improve wireless network performance. We study
network coding for one specific case of multicast, broadcasting, from one
source to all nodes of the network. We use network coding as a loss tolerant,
energy-efficient, method for broadcast. Our emphasis is on mobile networks. Our
contribution is the proposal of DRAGONCAST, a protocol to perform network
coding in such a dynamically evolving environment. It is based on three
building blocks: a method to permit real-time decoding of network coding, a
method to adjust the network coding transmission rates, and a method for
ensuring the termination of the broadcast. The performance and behavior of the
method are explored experimentally by simulations; they illustrate the
excellent performance of the protocol
Joint Routing and STDMA-based Scheduling to Minimize Delays in Grid Wireless Sensor Networks
In this report, we study the issue of delay optimization and energy
efficiency in grid wireless sensor networks (WSNs). We focus on STDMA (Spatial
Reuse TDMA)) scheduling, where a predefined cycle is repeated, and where each
node has fixed transmission opportunities during specific slots (defined by
colors). We assume a STDMA algorithm that takes advantage of the regularity of
grid topology to also provide a spatially periodic coloring ("tiling" of the
same color pattern). In this setting, the key challenges are: 1) minimizing the
average routing delay by ordering the slots in the cycle 2) being energy
efficient. Our work follows two directions: first, the baseline performance is
evaluated when nothing specific is done and the colors are randomly ordered in
the STDMA cycle. Then, we propose a solution, ORCHID that deliberately
constructs an efficient STDMA schedule. It proceeds in two steps. In the first
step, ORCHID starts form a colored grid and builds a hierarchical routing based
on these colors. In the second step, ORCHID builds a color ordering, by
considering jointly both routing and scheduling so as to ensure that any node
will reach a sink in a single STDMA cycle. We study the performance of these
solutions by means of simulations and modeling. Results show the excellent
performance of ORCHID in terms of delays and energy compared to a shortest path
routing that uses the delay as a heuristic. We also present the adaptation of
ORCHID to general networks under the SINR interference model
Heuristics for Network Coding in Wireless Networks
Multicast is a central challenge for emerging multi-hop wireless
architectures such as wireless mesh networks, because of its substantial cost
in terms of bandwidth. In this report, we study one specific case of multicast:
broadcasting, sending data from one source to all nodes, in a multi-hop
wireless network. The broadcast we focus on is based on network coding, a
promising avenue for reducing cost; previous work of ours showed that the
performance of network coding with simple heuristics is asymptotically optimal:
each transmission is beneficial to nearly every receiver. This is for
homogenous and large networks of the plan. But for small, sparse or for
inhomogeneous networks, some additional heuristics are required. This report
proposes such additional new heuristics (for selecting rates) for broadcasting
with network coding. Our heuristics are intended to use only simple local
topology information. We detail the logic of the heuristics, and with
experimental results, we illustrate the behavior of the heuristics, and
demonstrate their excellent performance
Near Optimal Broadcast with Network Coding in Large Sensor Networks
We study efficient broadcasting for wireless sensor networks, with network
coding. We address this issue for homogeneous sensor networks in the plane. Our
results are based on a simple principle (IREN/IRON), which sets the same rate
on most of the nodes (wireless links) of the network. With this rate selection,
we give a value of the maximum achievable broadcast rate of the source: our
central result is a proof of the value of the min-cut for such networks, viewed
as hypergraphs. Our metric for efficiency is the number of transmissions
necessary to transmit one packet from the source to every destination: we show
that IREN/IRON achieves near optimality for large networks; that is,
asymptotically, nearly every transmission brings new information from the
source to the receiver. As a consequence, network coding asymptotically
outperforms any scheme that does not use network coding.Comment: Dans First International Workshop on Information Theory for Sensor
Netwoks (WITS 2007) (2007
Computing connected dominated sets with multipoint relays
International audienceMultipoint relays offer an optimized way of flooding packets in a radio network. However, this technique requires the last hop knowledge: to decide whether or not a flooding packet is retransmitted, a node needs to know from which node the packet was received. When considering broadcasting at IP level, this information may be difficult to obtain. We thus propose a scheme for computing an optimized connected dominating set from multipoint relays. Proof of correctness and simulations are given for all these broadcasting mechanisms
Wireless Broadcast with Network Coding: Energy Efficiency, Optimality and Coding Gain in Lossless Wireless Networks
We consider broadcasting in multi-hop wireless networks, in which one source transmits information to all the nodes in the networks. We focus on energy efficiency, or minimizing the total number of transmissions. Our main result is the proof that, from the energy-efficiency perspective, network coding may essentially operate in an optimal way in the core of the network for uniform wireless networks in Euclidean spaces with idealized communication. In such networks, one corollary is that network coding is expected to outperform routing. We prove that the asymptotic network coding gain is comprised between 1.642 and 1.684 for networks of the plane, and comprised between 1.432 and 2.035 for networks in 3-dimensional space
Performance Evaluation of a Single Queue under Multi-User TCP/IP Connections
We study the performance of several TCP connections through the bottleneck of a slow network accessed via a single queue with high capacity. Using mean-field approximation methology, we establish some asymptotical results about queue length distribution and windo size distribution when the number of user increases proportionally to buffer capacity. We also give an evaluatio- n of TCP fairness under these traffic conditions
Stack Algorithms in Implicit Framing, Free Access and Blocked Access for CATV Networks
In this paper we present in the framework of access protocols for Cable TV (CATV) networks performant and easy implementation of stack algorithms with an implicit framing scheme. We use a stack algorithm with a single interleaved process in a free or blocked access mode. We show that the blocked access can be implemented to have a deterministic behaviour. We show that a dynamic tuning of the access persistence parameter improves the performance both in terms of throughput and delays
Wireless Broadcast with Network Coding: A Connected Dominating Sets Approach
We study network coding for multi-hop wireless networks. We focus the case of broadcasting, where one source transmits information to all the nodes in the network. Our goal is energy-efficient broadcasting, in other words, to minimize the number of transmissions for broadcasting to the entire network. To achieve this goal, we propose a family of methods that combine the use of network coding and connected dominating sets. They consists in rate selections using connected dominated sets (RAUDS: Rate Adjustment Using Dominating Sets, and an generalized version, MARAUDS). The main insight behind these methods is that their use of connected dominating sets, allows near-optimality in the core of the network, while they efficiently handle borders and non-uniformity. The main contribution is a formal proof of the performance of these families of algorithms. One main result is the comparison of performance between routing and these methods (and in general, network coding)
Stack Algorithms at High Loads : Analysis of Unfairness or Singular Behaviours
In this paper, we investigate the fairness of stack access algorithms in overload conditions. We show that conventional Last In First Out free-acces- s stack algorithms provide unfair channel access at high loads. A subset of end-users may starve during network overloads as the other nodes capture the whole channel capacity. We show that the First In First Out free-access stack protocol can cope with this unfairness problem. The blocked access stack algorithms are not showing unfairness problems
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