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An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. (DISCO)
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. (DISCO)
2010 (English)In: Proceedings of IEEE Global Telecommunications Conference (GLOBECOM) 2010, IEEE , 2010, 1-5 p.Conference paper, (Refereed)
Abstract [en]

Wireless mesh networks (WMNs) are wireless multihop networks comprised of mesh routers, which relay traffic on behalf of clients and other nodes. Using the standard IEEE 802.11 distributed coordination function (DCF) as MAC layer, a node needs to contend for the medium each time it wants to transmit a packet. This creates high overhead in particular for small packets and leads to poor performance for real-time applications such as Voice over IP (VoIP) or online gaming. Burst packet transmission can increase the efficiency. For example, with the Transmission Opportunity limit (TXOPlimit) in IEEE 802.11e, a station may transfer several packets without contending for the channel in between. Similarly, IP packet aggregation combines several IP packets together and sends them as one MAC Service Data Unit. Originally, both schemes have been developed for singlehop networks only. Thus the impact on WMNs is unclear if the packets need to contend over multiple hops. In this paper, we use measurements from a 9-node WMN testbed to compare TXOPs and IP packet aggregation for VoIP in terms of fairness, network capacity and quality of user experience. We show that for low networks loads, both TXOPs and IP packet aggregation increase the VoIP quality compared to IEEE 802.11 DCF. However, in highly loaded networks IP packet aggregation outperforms the other schemes.

Place, publisher, year, edition, pages
IEEE , 2010. 1-5 p.
Keyword [en]
Aggregates, Delay, IEEE 802.11e Standard, IP networks, Peer to peer computing, Receivers
National Category
Computer Science
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-6443DOI: 10.1109/GLOCOM.2010.5684219ISBN: 978-1-4244-5636-9 (print)OAI: oai:DiVA.org:kau-6443DiVA: diva2:354590
Conference
IEEE Global Telecommunications Conference (GLOBECOM) 2010, Miami, Florida, December 2010
Available from: 2012-03-19 Created: 2010-10-04 Last updated: 2012-03-20Bibliographically approved
In thesis
1. Cross-Layer Optimization of Voice over IP in Wireless Mesh Networks
Open this publication in new window or tab >>Cross-Layer Optimization of Voice over IP in Wireless Mesh Networks
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Wireless Mesh Networks (WMNs) have emerged as a promising network technology, which combines the benefits of cellular networks and Wireless Local Area Networks (WLANs). In a WMN mesh routers wirelessly relay traffic on behalf of other mesh routers or clients and thereby provide coverage areas comparable to cellular networks, while having the low complexity and low costs of WLANs. As Voice over IP (VoIP) is a very important Internet service, it is critical for the success of WMNs to support high quality VoIP. However, currentWMNs are not adapted well for VoIP. The capacity and scalability of single-radio WMNs is low, especially for small packet transmissions of VoIP calls, because the MAC and PHY layer overhead for small packets is high. The scalability of multiradio/multi-channel WMNs is usually higher, since fewer nodes contend for a channel. However channel scheduling might be required, which can lead to excessive delay and jitter and result in poor VoIP quality. In this thesis we investigate how to deliver high quality VoIP in single radio and multi-radio networks by using cross-layer optimization. For single radio WMNs, we consider the use of IP packet aggregation and IEEE 802.11e transmission opportunities. We conclude that IP packet aggregation greatly improves the capacity and thereby the scalability of WMNs. We show that the key for providing good quality is to artificially delay packets prior to aggregation. We propose a distributed cross-layer optimization system, which, based on Fuzzy Logic Inference, derives an aggregation delay that enhances the capacity and quality. For multi-radio/multi-channel WMNs, we demonstrate the importance of qualityof- service-aware channel scheduling. We develop a quality-of-serviceaware channel scheduler that compared to a basic round-robin scheme significantly reduces jitter and in that way increases VoIP quality. Our analysis shows that there is a trade-off between the jitter of high priority VoIP traffic and the throughput of background TCP traffic. The proposed optimizations significantly increase the capacity of singleradio and multi-radio WMNs. This allows network operators to serve more users with an existing mesh infrastructure or provide better service delivery to existing users.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2010. 33 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2010:25
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-6280 (URN)978-91-7063-309-6  (ISBN)
Presentation
2010-10-25, 21A 342, Karlstads universitet, Karlstad, 10:00 (English)
Opponent
Supervisors
Available from: 2010-10-08 Created: 2010-08-26 Last updated: 2011-10-24Bibliographically approved

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