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Autonomic wireless networking
KTH, School of Electrical Engineering (EES), Communication Networks.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Large-scale deployment of IEEE 802.11 wireless LANs (WLANs) remains a significant challenge. Many access points (APs) must be deployed and interconnected without a-priori knowledge of the demand. We consider that the deployment should be iterative, as follows. At first, access points are deployed to achieve partial coverage. Then, usage statistics are collected while the network operates. Overloaded and under-utilized APs would be identified, giving the opportunity to relocate, add or remove APs. In this thesis, we propose extensions to the WLAN architecture that would make our vision of iterative deployment feasible.

One line of work focuses on self-configuration, which deals with building a WLAN from APs deployed without planning, and coping with mismatches between offered load and available capacity. Self-configuration is considered at three levels. At the network level, we propose a new distribution system that forms a WLAN from a set of APs connected to different IP networks and supports AP auto-configuration, link-layer mobility, and sharing infrastructure between operators. At the inter-cell level, we design a load-balancing scheme for overlapping APs that increases the network throughput and reduces the cell delay by evenly distributing the load. We also suggest how to reduce the handoff time by early detection and fast active scanning. At the intra-cell level, we present a distributed admission control that protects cells against congestion by blocking stations whose MAC service time would be above a set threshold.

Another line of work deals with self-deployment and investigates how the network can assist in improving its continuous deployment by identifying the reasons for low cell throughput. One reason may be poor radio conditions. A new performance figure, the Multi-Rate Performance Index, is introduced to measure the efficiency of radio channel usage. Our measurements show that it identifies cells affected by bad radio conditions. An additional reason may be limited performance of some AP models. We present a method to measure the upper bound of an AP’s throughput and its dependence on offered load and orientation. Another reason for low throughput may be excessive distance between users and APs. Accurate positioning of users in a WLAN would permit optimizing the location and number of APs. We analyze the limitations of the two most popular range estimation techniques when used in WLANs: received signal strength and time of arrival. We find that the latter could perform better but the technique is not feasible due to the low resolution of the frame timestamps in the WLAN cards.

The combination of self-configuration and self-deployment enables the autonomic operation of WLANs.

Place, publisher, year, edition, pages
2005.
Keyword [en]
Electrical engineering, wireless LAN, autonomic communications
Keyword [sv]
Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-254OAI: oai:DiVA.org:kth-254DiVA: diva2:8166
Public defence
2005-06-10, Sal E3, Osquarsbacke 14, KTH main campus, 09:00
Opponent
Supervisors
Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2012-03-22
List of papers
1. Autonomic networking for wireless LANs
Open this publication in new window or tab >>Autonomic networking for wireless LANs
2005 (English)Report (Other academic)
Abstract [en]

We present extensions to the IEEE 802.11 WLAN architecture to facilitate the deployment and operation of large-scale networks. A new distribution system (DS) is designed to work across IP networks removingthe need for an Ethernet backbone. APs connected to different IP networkscan join the DS to form a single WLAN for users with link-layer mobility support. Two entities, portal and registry, are added to support selfconfiguration of access points, transport across the IP backbone and link layer mobility for stations. A novel feature of our DS design is the possibility that operators share some of their access points. Our proposed extensions are transparent to the stations; they do not require any modification to work with the new architecture.

Series
Trita-S3-LCN, ISSN 1653-0837 ; 0504
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5252 (URN)KTH/S3/LCN/--05/04--SE (ISRN)
Note
QC 20110207Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2013-09-09Bibliographically approved
2. Load balancing in overlapping wireless LAN cells
Open this publication in new window or tab >>Load balancing in overlapping wireless LAN cells
2004 (English)In: 2004 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-7, IEEE , 2004, 3833-3836 p.Conference paper, Published paper (Refereed)
Abstract [en]

We propose a load-balancing scheme for overlapping wireless LAN cells. Agents running in each access point broadcast periodically the local load level via the Ethernet backbone and determine whether the access point is overloaded, balanced or under-loaded by comparing it with received reports. The load metric is the access point throughput. Overloaded access points force the handoff of some stations to balance the load. Only under-loaded access points accept roaming stations to minimize the number of handoffs. We show via experimental evaluation that our balancing scheme increases the total wireless network throughput and decreases the cell delay.

Place, publisher, year, edition, pages
IEEE, 2004
Series
IEEE International Conference on Communications, ISSN 0536-1486
Keyword
Global system for mobile communications, Packet networks, Servers, Signal to noise ratio, Standardization, Telecommunication networks, Telecommunication traffic
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-5253 (URN)10.1109/ICC.2004.1313270 (DOI)000223459600745 ()2-s2.0-4143134344 (Scopus ID)0-7803-8533-0 (ISBN)
Conference
IEEE International Conference on Communications (ICC 2004) Location: Paris, France Date: JUN 20-24, 2004
Note

QC 20111024

Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2014-12-15Bibliographically approved
3. Techniques to reduce IEEE 802.11b handoff time
Open this publication in new window or tab >>Techniques to reduce IEEE 802.11b handoff time
2004 (English)In: 2004 IEEE International Conference on Communications, Vols 1-7, IEEE , 2004, 3844-3848 p.Conference paper, Published paper (Refereed)
Abstract [en]

We analyze the link-layer handoff process in wireless LANs based on the IEEE 802.11b standard and suggest how to reduce its duration. Firstly, we divide the process into three phases: detection, search and execution. Our performance measurements indicate that the detection and search phases are the main contributors to the handoff time. We show that the link-layer detection time can be reduced to three consecutive lost frames. We also show that the search time can be reduced at least by 20% using active scanning with the two timers that control its duration set to 1 ms and 10.24 ms. Several simulations illustrate the achieved reduction in handoff time.

Place, publisher, year, edition, pages
IEEE, 2004
Series
IEEE International Conference on Communications, ISSN 1550-3607
Keyword
wireless LAN, handoff, performance
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-5254 (URN)10.1109/ICC.2004.1313272 (DOI)000223459600747 ()2-s2.0-4143090506 (Scopus ID)0-7803-8533-0 (ISBN)
Conference
IEEE International Conference on Communications (ICC 2004). Paris, FRANCE. JUN 20-24, 2004
Note

QC 20111020

Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2014-12-11Bibliographically approved
4. Distributed admission control for WLANs
Open this publication in new window or tab >>Distributed admission control for WLANs
2005 (English)Report (Other academic)
Series
Trita-S3-LCN, ISSN 1653-0837 ; 0502
National Category
Computer and Information Science Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5255 (URN)KTH/S3/LCN/--05/02--SE (ISRN)
Note
QC 20110207Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2013-09-09Bibliographically approved
5. Statistical analysis of the IEEE 802.11 MAC service time
Open this publication in new window or tab >>Statistical analysis of the IEEE 802.11 MAC service time
2005 (English)In: Performance Challenges for Efficient Next Generation Networks, 2005, 2257-2266 p.Conference paper, Published paper (Refereed)
Abstract [en]

We present a statistical analysis of the IEEE 802.11 MAC service time. Our analysis complements the results from mathematical models, which focus on the mean delay. The location analysis shows that the service time's distribution is skewed: the mean is always larger than the median, and the mode is always the smallest. A deeper analysis of the mean illustrates its dependence on the number of stations in the cell, the offered load, the packet size and the bit rate. The analysis of variability includes the coefficient of variation of the service time and its cumulative distribution function. The high variability found indicates that the 95-percentile of the service time may be a more meaningful measure than the mean. Finally, the analysis of correlation demonstrates that the service time of a packet is not predictable from the service time of previous packets.

Keyword
IEEE 802.11 MAC, service time, analysis
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-5256 (URN)000232398502029 ()
Conference
19th International Teletraffic Congress (ITC 19) Beijing, PEOPLES R CHINA, AUG 29-SEP 02, 2005
Note
QC 20110705Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2013-09-09Bibliographically approved
6. Multi-rate performance index for wireless LANs
Open this publication in new window or tab >>Multi-rate performance index for wireless LANs
2004 (English)In: 2004 IEEE 15TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-4, PROCEEDINGS, NEW YORK, NY: IEEE , 2004, 1154-1157 p.Conference paper, Published paper (Refereed)
Abstract [en]

The throughput per access point has been used as the main figure of merit in performance characterization of wireless LANs. The usefulness of throughput as a performance measure is limited because low throughput can be produced by either low offered traffic or by radio conditions that limit the data rates. In this paper, we propose the Multi-rate Performance Index as an additional figure of merit to characterize the performance of wireless LAN cells. It represents which bit rates are used in the cell, and therefore it identifies cells whose throughput is limited by radio conditions rather than offered traffic. We include several measurements in real cells to illustrate its utility in performance analysis.

Place, publisher, year, edition, pages
NEW YORK, NY: IEEE, 2004
Keyword
wireless LAN, performance, metric
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-5257 (URN)10.1109/PIMRC.2004.1373879 (DOI)000225483300224 ()2-s2.0-11244352371 (Scopus ID)0-7803-8523-3 (ISBN)
Conference
15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004). Barcelona, SPAIN. SEP 05-08, 2004
Note
QC 20111020Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2013-09-09Bibliographically approved
7. Performance measurements of the saturation throughput in IEEE 802.11 access points
Open this publication in new window or tab >>Performance measurements of the saturation throughput in IEEE 802.11 access points
2005 (English)In: Proceedings of the Third International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, 2005, 129-138 p.Conference paper, Published paper (Refereed)
Abstract [en]

Performance measurements of IEEE 802.11 access points provide important information for networking research and network management. In this paper, we present an active measurement method to determine the maximum saturation throughput of wireless LAN access points. The saturation throughput is achieved when there always is a frame ready to transmit, and it reaches the maximum for optimal transmission conditions. We use the proposed method to measure and analyze the performance of five IEEE 802.11b access points. The results show the strength of our method and identify performance characteristics of commercial access points. The analysis produces the following results. The maximum saturation throughput shows significant differences between models. Increasing the offered load to the access point's Ethernet interface does not always increase the throughput; a few access points present a downlink throughput reduction when the offered load exceeds their bridging capabilities. Some access points exhibit better performance in certain orientations.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-5258 (URN)000230463100015 ()2-s2.0-33744462337 (Scopus ID)0-7695-2267-X (ISBN)
Conference
3rd International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks Location: Riva del Garda, ITALY Date: APR 04-06, 2005
Note
QC 20111017Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2011-10-17Bibliographically approved
8. Limitations of range estimation in wireless LAN
Open this publication in new window or tab >>Limitations of range estimation in wireless LAN
2004 (English)In: Proceedings of 1st Workshop on Positioning, Navigation and Communication, WPNC'04, 2004Chapter in book (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5259 (URN)
Note
QC 20111115Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2013-09-09Bibliographically approved

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Citation style
  • apa
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  • Other locale
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Output format
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