Introduction
This lab will introduce you to wireless spectrum analysis and supports this week’s TCO.
TCO 7: Given a situation requiring a wireless network solution, propose an appropriate design for a wireless network using radio frequency based methods.
Background
Wireless signals are invisible to the human eye. To see these signals, a tool such as a spectrum analyzer is required. In this lab, you will learn how to use a common spectrum analyzer, as you would in your career, to locate potential interference while designing a wireless local area network.
iLab Instructions
1. Review the Tutorial: Using a Spectrum Analyzer located in Appendix A.
2. Download NETW360W5iLabFiles.zip from Doc Sharing to a working directory on your computer. Once the file is downloaded, unzip (expand) the contents of the zip file. A directory, NETW360W5iLab, will be created and contain the following files:
1. Chanalyzer_Installer.3.4.msi: Installation program that installs Chanalyzer on your computer 2. Capture1.wsr: First, capture file for analysis 3. Capture2.wsr: Second, capture file for analysis 4. Capture3.wsr: Third, wireless capture file for analysis 5. Capture4.wsr: Fourth, wireless capture file for analysis
3. Install the Chanalyzer spectrum analysis program by double-clicking on the Chanalyzer_Installer.3.4.msi file.
4. Start the Chanalyzer. Once the Chanalyzer is running, open the first capture file, Capture1.wsr, and let the recording run for a few minutes. Using this capture, answer the following questions in your lab report.
Question 1: Are any channels being used that overlap other channels?
Question 2: If you had to install a new wireless LAN, what channel would you use?
5. Close Capture1.wsr and open the file Capture2.wsr. Let the recording run for a few minutes. Using this capture, answer the following questions in your lab report.
Question 3: What channels are being used?
Question 4: What channel is being used the most?
6. Close Capture2.wsr and open Capture3.wsr. Let the recording run for a few minutes. Using this capture, answer the following questions in your lab report.
Question 5: What type of signal is being shown?
Question 6: What frequency, not channel, is being used?
7. Close Capture3.wsr and open Capture4.wsr. Let the recording run for a few minutes. Using this capture, answer the following questions in your lab report.
Question 7: What type of signal is being shown?
Question 8: How strong is this signal in dBms?
8. Exit the Chanalyzer. The lab is complete.
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Appendix A
Tutorial: Using a Spectrum Analyzer
In this lab, we will examine how to use a USB-based spectrum analyzer. The device used will be the W-Spy USB spectrum analyzer from Metageek at www.metageek.net.
This device looks like this:
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To display what is captured by this device, Metageek provides the Chanalyzer program. Interface is shown below.
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The moving line at the bottom shows how long the data has been captured. In this case, it was for 29 seconds.
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The top window is the Spectral view and is shown below. The color bar at the top shows the signal strength. The number on the left is the weakest. The number on the right is the strongest. The colors in this view represent the signal strength. Vertical stripes in the Spectral view indicate a steady signal. The color of the stripes shows how strong the signal is. In this case, it shows a weak but constant signal.
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The middle window is the Topographic view and shows the signal patterns again using a color code. The signal strength, in dBs, is shown on the left.
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The bottom window is the Planar view and shows the signal strength. This view can show three different signals, the current signal is in yellow, the average signal is in green, and the maximum signal is in blue. The signal strength, in dBs, is shown on the left.
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In the Planar view, each of these three signals can be turned on or off by clicking its name in the upper right corner. When looking for interference, it is best to turn off the maximum and average signals and only display current signal (yellow) strength indicator.
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Many common signal signatures can be accessed by clicking on the Signatures tab on the right side of the interface. These can be selected, and then moved over the signal shown to help identify a pattern, as shown in the two images below.
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Capturing data—not required for this iLab
Notes for capturing data: Recall that a spectrum analyzer shows both non-802.11 signals and 802.11a/b/g/n signals. The 802.11 signals can be overlaid onto the displayed signals.
This requires that a wireless NIC be present in the same system that the USB spectrum analyzer is connected to. To do this, select the Wi-Fi tab, then click Start Scanning. Once the network list is complete, select the ones to show on the spectrum display by clicking the boxes. As can be seen in the following images, valuable details can be observed by hovering over the list.
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