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Written by Jim Geier
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Saturday, 17 March 2007 |
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In addition to microwave ovens, cordless phones cause significant interference in the 2.4GHz band (i.e., 802.11b and 802.11g). To see what interference from a 2.4GHz cordless phone looks like (implementing FHSS), look at the screen shot of a spectrum analyzer below, This measurement was taken within a few feet of the cordless phone handset, and the signal is present during the entire phone call. An issue with FHSS, is that it spreads across the entire band, as you can see in the image. As a result, it’s not possible to tune wireless LAN access points away from FHSS interference. At least the amplitude of FHSS signals appear to be lower than those from operating microwave ovens. | |
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Written by Jim Geier
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Saturday, 17 March 2007 |
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 We recently performed a pre-installation RF study of the entire San Francisco area (50 square miles) by driving around the streets and collecting RF data. This was a bit challenging due to the many hills and heavy traffic, but the sights were amazing! Part of our job was to record a hundred spectrum scans throughout the City. In order to do this, we used AirMagnet Survey software integrated with a GPS and AirMagnet’s Analyzer Adapter, which fits in the PCMCIA slot on a laptop. The software automatically records a spectrum scan in both the 2.4-2.5GHz and 5.0-6.0GHz frequency bands every few seconds while we drove. This was much easier than using a portable spectrum analyzer to record the scans manually.
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Written by Jim Geier
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Saturday, 17 March 2007 |
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Understand how 802.11 multicast traffic can degrade battery life.
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