Experiments of Some Performance Issues with IEEE 802.11b in Ad Hoc Networks

Chaudet, Claude; Dhoutaut, Dominique; Lassous, Isabelle Guérin

doi:10.1109/wons.2005.16

Cited by 20 publications

(23 citation statements)

References 10 publications

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“…While a number of studies have analyzed short-term unfairness due to various aspects of the wireless medium ranging from channel errors to contention, (see [1,5,6] for example), none accurately characterize the time scale in which 802.11 stations alternate domination in SIS scenarios. In particular, in our analysis of the SIS group, we model short-term unfairness of IEEE 802.11 with and without RTS/CTS, derive the behavior of the flows from the collision probability, analyze the transient behavior of the system, and accurately predict the timescale of this unfairness as a function of key system parameters.…”

Section: Related Workmentioning

confidence: 99%

Modeling media access in embedded two-flow topologies of multi-hop wireless networks

Garetto

Shi

Knightly

2005

Proceedings of the 11th Annual International Conference on Mobile Computing and Networking

108

153

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In this paper, we decompose a large-or small-scale multi-hop wireless network into embedded subgraphs, each consisting of four nodes and two flow pairs. We systematically study all twelve possible topologies that arise according to whether the different nodes are in radio range of each other. We show that under both a random spatial distribution of nodes and random waypoint mobility with shortest-path routing, a critical and highly probable scenario is a class in which the channel state shared by the two flows is not only incomplete (i.e., the graph is not fully connected), but there is also asymmetry in the state between the two flows. We develop an accurate analytical model validated by simulations to characterize the long-term unfairness that naturally arises when CSMA with twoor four-way handshake is employed as a random access protocol. Moreover, we show that another key class of topologies consists of incomplete but symmetric shared state. We show via modeling and simulations that in this case, the system achieves long-term fairness, yet endures significant durations in which one flow dominates channel access with many repeated transmissions before relinquishing the channel. The model predicts the time-scales of this unfairness as a function of system parameters such as the maximum retransmission limit.

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Section: Related Workmentioning

confidence: 99%

Modeling media access in embedded two-flow topologies of multi-hop wireless networks

Garetto

Shi

Knightly

2005

Proceedings of the 11th Annual International Conference on Mobile Computing and Networking

108

153

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“…The unfairness of 802.11 is due to the topological advantage of the links at the border of the network, over the ones in the center: the former compete with fewer links than the latter, and can therefore access the channel more often, this is often refer to as the "Flow in the Middle" problem (see e.g. [9,10]). The ratio λ/μ indicates how far this effect propagates in the network, as shown in Figure 3.…”

Section: Fairnessmentioning

confidence: 99%

Models of 802.11 multi-hop networks: Theoretical insights and experimental validation

Aziz

Durvy²,

Dousse³

et al. 2011

2011 Third International Conference on Communication Systems and Networks (COMSNETS 2011)

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Abstract-Wireless Multi-Hop CSMA/CA Networks are challenging to analyze. On the one hand, their dynamics are complex and rather subtle effects may severely affect their performance. Yet, understanding these effects is critical to operate upper layer protocols, such as TCP/IP. On the other hand, their models tend to be very complex in order to reproduce all the features of the protocol. As a result, they do not convey much insight into the essential features.We review two models of 802.11 protocols, which are simple enough to first explain why a trade-off needs to be found between fairness and spatial reuse (throughput) in saturated wireless networks (where all nodes have packets to transmit to their neighbors); and then to explain why non-saturated networks (where only some nodes, the sources, have packets to transmit to their destinations in a multi-hop fashion) that are more than 3 hops longs suffer from instability. We confront both models either to realistic simulations in ns-2 or to experiments with a testbed deployed at EPFL. We find that the predictions of both models help us understand the performance of the 802.11 protocol, and provide hints about the changes that need to be brought to the protocol.

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“…However, broadcasts in ad hoc networks normally do not use RTS/CTS, and for data transmission it is optional. Also the effectiveness of RTS/CTS handshake is questionable, e.g., many theoretical studies, simulations, and real world experiments show that when no RTS/CTS handshake is used, a network's throughput improves [9,36].…”

Section: Related Workmentioning

confidence: 99%

“…The beaconing interval of GPSR is left at the default value -3 s. In case of GPSR we want to test only the ability of this protocol to successfully route data packets to their destinations in VANETs by employing greedy forwarding and perimeter mode routing 9 . Thus, we do not use any location service, but rather provide coordinates of destination from the simulator's global knowledge.…”

Section: Simulation Setupmentioning

confidence: 99%

See 1 more Smart Citation

An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

Naumov

Baumann

Groß

2006

Proceedings of the 7th ACM International Symposium on Mobile Ad Hoc Networking and Computing

403

215

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Vehicular ad hoc networks (VANETs) using WLAN technology have recently received considerable attention. The evaluation of VANET routing protocols often involves simulators since management and operation of a large number of real vehicular nodes is expensive. We study the behavior of routing protocols in VANETs by using mobility information obtained from a microscopic vehicular traffic simulator that is based on the on the real road maps of Switzerland. The performance of AODV and GPSR is significantly influenced by the choice of mobility model, and we observe a significantly reduced packet delivery ratio when employing the realistic traffic simulator to control mobility of nodes. To address the performance limitations of communication protocols in VANETs, we investigate two improvements that increase the packet delivery ratio and reduce the delay until the first packet arrives. The traces used in this study are available for public download.

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Experiments of Some Performance Issues with IEEE 802.11b in Ad Hoc Networks

Cited by 20 publications

References 10 publications

Modeling media access in embedded two-flow topologies of multi-hop wireless networks

Modeling media access in embedded two-flow topologies of multi-hop wireless networks

Models of 802.11 multi-hop networks: Theoretical insights and experimental validation

An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

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