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Performance measurements of the saturation throughput in IEEE 802.11 access points
KTH, School of Electrical Engineering (EES).
KTH, School of Electrical Engineering (EES), Communication Networks.
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 (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.

Place, publisher, year, edition, pages
2005. 129-138 p.
National Category
URN: urn:nbn:se:kth:diva-5258ISI: 000230463100015ScopusID: 2-s2.0-33744462337ISBN: 0-7695-2267-XOAI: diva2:8164
3rd International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks Location: Riva del Garda, ITALY Date: APR 04-06, 2005
QC 20111017Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2011-10-17Bibliographically approved
In thesis
1. Autonomic wireless networking
Open this publication in new window or tab >>Autonomic wireless networking
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.

Electrical engineering, wireless LAN, autonomic communications, Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-254 (URN)
Public defence
2005-06-10, Sal E3, Osquarsbacke 14, KTH main campus, 09:00
Available from: 2005-06-01 Created: 2005-06-01 Last updated: 2012-03-22

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