[Spectrum Analysis of a Wireless Network]
Wireless network automationJoint SCS 2005-2006 Undergraduate Thesis
| Student: | Advisor: |
| Ilsun Li | Peter Steenkiste |
| Yuxiang Liu | Srinivasan Seshan |
Introduction
Today there are many access points and wireless enabled laptops in one's home and office. The number wireless devices will continue increase rapidly in the near future as the cost decreases. Since there are only three non-interfering channels in 802.11, interference between wireless devices will increase dramatically and thus decrease the performance of these devices. Spectrum scarcity will be a major problem in the near future. One solution to this problem is to actively monitor the spectrum usage in a particular area and efficiently allocate the spectrum as needed to wireless devices.
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The Problem
In a large wireless network deployment, there are many questions for which the answers are either very expensive or even impossible to find. For example:
- How does a network administrator determine if a drop in network efficiency of one access point is due to interference from nearby access points or increase in load?
- How does one access point A tell access point B that access point B is interfering with A's communication?
- How do I make the access points configure itself so I won't have to worry about these questions?
Currently, to answer these questions, a network administrator must be perform a very expensive site survey. While the site survey will inform the administrator about any network interference and help him or her configure the wireless network, it will not provide constant monitoring to inform him or her of a change in the wireless network environment.
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The Solution
Our solution to monitoring the spectrum usage of a wireless network and configuration of the access points is to put the monitoring software and configuration software on the access points themselves. This way, a network administrator could simply add new access points in any convenient area with a network connection and not worry about the new access points adversely affect the existing deployment. The new access points will retrieve the current picture of the wireless network from the old access points and configure themselves accordingly.
Obaining an image of the current wireless spectrum
Our solution depends on the ability of our monitoring software to build a local image of the wireless spectrum on each access point and share that image to the entire network to build a global tapestry of the wireless spectrum.
To do so, the monitoring software on each access point takes note of some ethernet header information of each incoming and outgoing packet. The information that it saves are:
- The received signal strength of the packet
- The size of the packet
- The transmission rate of the packet
- The transmitter and receiver of the packet identified by their MAC addresses
Every minute, a average of these readings are sent to a server for analysis. All other data are discarded. Since we only look at the data link layer of each packet, we do not store your IP address, any end-to-end information or any data that you sent or received.
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