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Generic stationary backoff distributions for distributed multiple access control
Umeå University, Faculty of Science and Technology, Department of Computing Science.
2014 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 56, no 3, 383-398 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we study the characteristics of two different backoff schemes: one that maximizes the channel utilization and one that maximizes the probability of a successful transmission. Our results indicate that while the latter provides slightly lower channel utilization, its shape is much less sensitive to the number of contending nodes. That is, the channel utilization is kept almost constant for a very wide range of node densities if the backoff distribution has increasing shape. This motivates us to propose a simple heuristic backoff scheme called the Truncated Geometric Backoff Distribution (TGBD). We provide simple analytical expressions for the probability of a successful transmission and the channel utilization. We also show that the TGBD can easily be extended to support service differentiation by adjusting the window lengths, and we provide a simple approximation that gives the relative share of the capacity for a node in a priority class compared to nodes in other classes. This extended backoff scheme easily outperforms the much more complex Quality of Service (QoS) standard, IEEE802.11e EDCA. Finally, a two-stage backoff model, based on the TGBD, is proposed that further increases the probability of a successful transmission. Results indicate that the channel utilization is almost independent of the number of contending nodes.

Place, publisher, year, edition, pages
Dordrecht: Springer, 2014. Vol. 56, no 3, 383-398 p.
Keyword [en]
Stationary backoff distribution, Performance modeling, QoS, IEEE 802.11, IEEE 802.11e
National Category
URN: urn:nbn:se:umu:diva-2911DOI: 10.1007/s11235-013-9851-6ISI: 000338231800007OAI: diva2:141256
Available from: 2008-01-24 Created: 2008-01-24 Last updated: 2016-08-26Bibliographically approved
In thesis
1. Distributed Multiple Access and Service Differentiation Algorithms for Wireless Networks
Open this publication in new window or tab >>Distributed Multiple Access and Service Differentiation Algorithms for Wireless Networks
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Communicating over a wireless channel poses many unique challenges not found in wired communication because of the special characteristics of the wireless channel. The capacity in a wireless network is typically scarce as a result of the limited bandwidth and many distinct phenomenons, like attenuation and interference, that work destructively on the received signals.

The Medium Access Control (MAC) layer is responsible for sharing this limited resource among the users. This allocation problem should be handled by considering the Quality of Service (QoS) requirements of each user as to maximize the utility. Efficient MAC algorithms are crucial in minimizing collisions between transmissions and thus achieving high utilization of the channel.

This thesis focuses on conflict resolution and service differentiation algorithms for wireless local area networks, where there is no central control of the channel and each sender independently contends for access.

In part I, we study three approaches to improve the IEEE 802.11(e) standards with focus on QoS. In the first approach, utility functions are considered, that model application preferences, to achieve service differentiation and maximize the aggregated utility. We provide algorithms for two subsidiary problems that arise from the maximization problem, and show that a near--optimal solution is found. In the second approach a collision detection algorithm for multicast transmissions is proposed, that increases the reliability for multicast compared to the protected unicast traffic. The third approach is an improved MAC algorithm for the QoS standard IEEE 802.11e. The improved algorithm outperforms the standard and achieves close to optimal performance for large number of scenarios, which significantly reduces the need of adjusting the contention parameters.

In part II, we focus on channel bursting protocols that use noise bursts to resolve channel conflicts. These protocols is capable of achieving very low collision probability. We propose two new bursting protocols, that achieve very high channel utilization, and show that the bursting technique has good fairness properties and provides efficient support for service differentiation. We also show that it is possible to reduce the number of bursts without loosing performance.

In part III, the optimal backoff distribution that minimizes the collision probability is derived. We then propose a heuristic backoff distribution with similar properties that yields high channel utilization. An extension for service differentiation is provided where the sizes of the backoff windows are adjusted.

Place, publisher, year, edition, pages
Umeå: Datavetenskap, 2008. 34 p.
Report / UMINF, ISSN 0348-0542 ; 08.01
Wireless Local Area Networks, Medium Access Control, Quality of Service, Resource Allocation, IEEE 802.11, IEEE 802.11e
National Category
urn:nbn:se:umu:diva-1506 (URN)978-91-7264-487-8 (ISBN)
Public defence
2008-02-14, MA121, MIT huset, SE-901 87, Umeå, 13:00
Available from: 2008-01-24 Created: 2008-01-24Bibliographically approved

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