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Cross-Layer Optimization of Voice over IP in Wireless Mesh Networks
Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. (Computer Science)
2010 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Karlstad: Karlstad University , 2010. , s. 33
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2010:25
Nationell ämneskategori
Datavetenskap (datalogi)
Forskningsämne
Datavetenskap
Identifikatorer
URN: urn:nbn:se:kau:diva-6280ISBN: 978-91-7063-309-6  (tryckt)OAI: oai:DiVA.org:kau-6280DiVA, id: diva2:345616
Presentation
2010-10-25, 21A 342, Karlstads universitet, Karlstad, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2010-10-08 Skapad: 2010-08-26 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
Delarbeten
1. Theoretical and Experimental Analysis of the Channel Busy Fraction in IEEE 802.11
Öppna denna publikation i ny flik eller fönster >>Theoretical and Experimental Analysis of the Channel Busy Fraction in IEEE 802.11
2010 (Engelska)Ingår i: Proceedings of Future Network & Mobile Summit 2010, IEEE , 2010, s. 1-9Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Optimizing the operation of IEEE 802.11 networks requires to estimate the load of the wireless channel. The channel busy fraction, which is the fraction of time in which the wireless channel is sensed busy due to successful or unsuccessful transmissions, can be used as such indicator. It can be obtained from e.g. the IEEE 802.11k channel load report or hardware-specific interfaces. Previously, the channel busy fraction has been used as a metric for different purposes such as routing and admission control. However, a thorough evaluation of the relationship between the busy fraction and other important characteristics such as the collision probability and throughput is missing. In this paper, we present an analytical model to study the channel busy fraction in non-saturated IEEE 802.11 networks. We validate the model with measurements in a testbed. The predictions from the model match measurements well. Furthermore, we demonstrate how to apply the model to estimate the available link bandwidth. Using measurements obtained from a testbed operated at 6 Mbit/s, we show that the channel busy fraction allows an accurate prediction of the available bandwidth with an error smaller than 70 Kbit/s.

Ort, förlag, år, upplaga, sidor
IEEE, 2010
Nyckelord
Analytical models, Channel estimation, IEEE 802.11 Standards, Load modeling, Measurement, Throughput, Wireless sensor networks
Nationell ämneskategori
Datavetenskap (datalogi)
Forskningsämne
Datavetenskap
Identifikatorer
urn:nbn:se:kau:diva-6442 (URN)978-1-905824-16-8 (ISBN)
Konferens
Future Network & Mobile Summit 2010, Florence, Italy, June 2010
Tillgänglig från: 2010-10-04 Skapad: 2010-10-04 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
2. An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks
Öppna denna publikation i ny flik eller fönster >>An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks
2010 (Engelska)Ingår i: Proceedings of IEEE Global Telecommunications Conference (GLOBECOM) 2010, IEEE , 2010, s. 1-5Konferensbidrag, Publicerat paper (Refereegranskat)
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.

Ort, förlag, år, upplaga, sidor
IEEE, 2010
Nyckelord
Aggregates, Delay, IEEE 802.11e Standard, IP networks, Peer to peer computing, Receivers
Nationell ämneskategori
Datavetenskap (datalogi)
Forskningsämne
Datavetenskap
Identifikatorer
urn:nbn:se:kau:diva-6443 (URN)10.1109/GLOCOM.2010.5684219 (DOI)978-1-4244-5636-9 (ISBN)
Konferens
IEEE Global Telecommunications Conference (GLOBECOM) 2010, Miami, Florida, December 2010
Tillgänglig från: 2012-03-19 Skapad: 2010-10-04 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
3. FUZPAG: A Fuzzy-Controlled Packet Aggregation Scheme for Wireless Mesh Networks
Öppna denna publikation i ny flik eller fönster >>FUZPAG: A Fuzzy-Controlled Packet Aggregation Scheme for Wireless Mesh Networks
Visa övriga...
2010 (Engelska)Ingår i: Proceedings of the International Conference on Fuzzy Systems and Knowledge Discovery (FSKD'10), IEEE , 2010, s. 778-782Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Wireless mesh networks (WMNs) are wireless multi-hop backhaul networks in which mesh routers relay traffic on behalf of clients or other routers. Due to large MAC layer overhead, applications such as Voice over IP, which send many small packets, show poor performance in WMNs. Packet aggregation increases the capacity of IEEE 802.11-based WMNs by aggregating small packets into larger ones and thereby reducing overhead. In order to have enough packets to aggregate, packets need to be delayed and buffered. Current aggregation mechanisms use fixed buffer delays or do not take into account the delay characteristics of the saturated IEEE 802.11 MAC layer. In this work, we present FUZPAG, a novel packet aggregation architecture for IEEE 802.11-based wireless mesh networks. It uses fuzzy control to determine the optimum aggregation buffer delay under the current channel utilization. By cooperation among neighboring nodes FUZPAG distributes the buffer delay in a fair way. We implemented and evaluated the system in a wireless mesh testbed. For different network topologies we show that FUZPAG outperforms standard aggregation in terms of end-to-end latency under a wide range of traffic patterns.

Ort, förlag, år, upplaga, sidor
IEEE, 2010
Nyckelord
Aggregates, Delay, Fuzzy control, IEEE 802.11 Standards, Throughput, Wireless communication, Wireless mesh networks
Nationell ämneskategori
Datavetenskap (datalogi)
Forskningsämne
Datavetenskap
Identifikatorer
urn:nbn:se:kau:diva-6444 (URN)10.1109/FSKD.2010.5569346 (DOI)978-1-4244-5931-5 (ISBN)
Konferens
The International Conference on Fuzzy Systems and Knowledge Discovery (FSKD'10), Yantai, China, August 2010
Tillgänglig från: 2012-03-19 Skapad: 2010-10-04 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
4. QoS-Aware Channel Scheduling for Multi-Radio/Multi-Channel Wireless Mesh Networks
Öppna denna publikation i ny flik eller fönster >>QoS-Aware Channel Scheduling for Multi-Radio/Multi-Channel Wireless Mesh Networks
2009 (Engelska)Ingår i: Proceedings of the Fourth ACM International Workshop on Wireless Network Testbeds, Experimental evaluation and Characterization (WiNTECH 09), New York: ACM , 2009Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In non-static multi-radio/multi-channel wireless mesh networks architectures such as Net-X, mesh nodes need to switch channels in order to communicate with different neighbors. Present channel schedulers do not consider the requirements of real time traffic such as voice over IP. Thus the resulting quality is low. We propose a novel channel scheduler for the Net-X platform that takes into account packet priorities. We evaluate the algorithm on the KAUMesh testbed. Our algorithm outperforms the standard round-robin scheduler both in terms of average delay and jitter.

Ort, förlag, år, upplaga, sidor
New York: ACM, 2009
Nationell ämneskategori
Datavetenskap (datalogi)
Forskningsämne
Datavetenskap
Identifikatorer
urn:nbn:se:kau:diva-6445 (URN)10.1145/1614293.1614296 (DOI)978-1-60558-740-0 (ISBN)
Konferens
The Fourth ACM International Workshop on Wireless Network Testbeds, Experimental evaluation and Characterization (WiNTECH 09), Beijing, China, September 2009
Tillgänglig från: 2010-10-04 Skapad: 2010-10-04 Senast uppdaterad: 2018-01-12Bibliografiskt granskad

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