Email Delivery

Receive new posts as email.

Email address

Syndicate this site

RSS | Atom

Contact

About This Site
Contact Us
Privacy Policy

Search


November 2010
Sun Mon Tues Wed Thurs Fri Sat
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30        

Stories by Category

Basics :: Basics
Casting :: Casting Listen In Podcasts Videocasts
Culture :: Culture Hacking
Deals :: Deals
FAQ :: FAQ
Future :: Future
Hardware :: Hardware Adapters Appliances Chips Consumer Electronics Gaming Home Entertainment Music Photography Video Gadgets Mesh Monitoring and Testing PDAs Phones Smartphones
Industry :: Industry Conferences Financial Free Health Legal Research Vendor analysis
International :: International
Media :: Media Locally cached Streaming
Metro-Scale Networks :: Metro-Scale Networks Community Networking Municipal
Network Types :: Network Types Broadband Wireless Cellular 2.5G and 3G 4G Power Line Satellite
News :: News Mainstream Media
Politics :: Politics Regulation Sock Puppets
Schedules :: Schedules
Security :: Security 802.1X
Site Specific :: Site Specific Administrative Detail April Fool's Blogging Book review Cluelessness Guest Commentary History Humor Self-Promotion Unique Wee-Fi Who's Hot Today?
Software :: Software Open Source
Spectrum :: Spectrum 60 GHz
Standards :: Standards 802.11a 802.11ac 802.11ad 802.11e 802.11g 802.11n 802.20 Bluetooth MIMO UWB WiGig WiMAX ZigBee
Transportation and Lodging :: Transportation and Lodging Air Travel Aquatic Commuting Hotels Rails
Unclassified :: Unclassified
Vertical Markets :: Vertical Markets Academia Enterprise WLAN Switches Home Hot Spot Aggregators Hot Spot Advertising Road Warrior Roaming Libraries Location Medical Public Safety Residential Rural SOHO Small-Medium Sized Business Universities Utilities wISP
Voice :: Voice

Archives

November 2010 | October 2010 | September 2010 | August 2010 | July 2010 | June 2010 | May 2010 | April 2010 | March 2010 | February 2010 | January 2010 | December 2009 | November 2009 | October 2009 | September 2009 | August 2009 | July 2009 | June 2009 | May 2009 | April 2009 | March 2009 | February 2009 | January 2009 | December 2008 | November 2008 | October 2008 | September 2008 | August 2008 | July 2008 | June 2008 | May 2008 | April 2008 | March 2008 | February 2008 | January 2008 | December 2007 | November 2007 | October 2007 | September 2007 | August 2007 | July 2007 | June 2007 | May 2007 | April 2007 | March 2007 | February 2007 | January 2007 | December 2006 | November 2006 | October 2006 | September 2006 | August 2006 | July 2006 | June 2006 | May 2006 | April 2006 | March 2006 | February 2006 | January 2006 | December 2005 | November 2005 | October 2005 | September 2005 | August 2005 | July 2005 | June 2005 | May 2005 | April 2005 | March 2005 | February 2005 | January 2005 | December 2004 | November 2004 | October 2004 | September 2004 | August 2004 | July 2004 | June 2004 | May 2004 | April 2004 | March 2004 | February 2004 | January 2004 | December 2003 | November 2003 | October 2003 | September 2003 | August 2003 | July 2003 | June 2003 | May 2003 | April 2003 | March 2003 | February 2003 | January 2003 | December 2002 | November 2002 | October 2002 | September 2002 | August 2002 | July 2002 | June 2002 | May 2002 | April 2002 | March 2002 | February 2002 | January 2002 | December 2001 | November 2001 | October 2001 | September 2001 | August 2001 | July 2001 | June 2001 | May 2001 | April 2001 |

Recent Entries

In-Flight Wi-Fi and In-Flight Bombs
Can WPA Protect against Firesheep on Same Network?
Southwest Sets In-Flight Wi-Fi at $5
Eye-Fi Adds a View for Web Access
Firesheep Makes Sidejacking Easy
Wi-Fi Direct Certification Starts
Decaf on the Starbucks Digital Network
Google Did Snag Passwords
WiMax and LTE Not Technically 4G by ITU Standards
AT&T Wi-Fi Connections Keep High Growth with Free Service

Site Philosophy

This site operates as an independent editorial operation. Advertising, sponsorships, and other non-editorial materials represent the opinions and messages of their respective origins, and not of the site operator. Part of the FM Tech advertising network.

Copyright

Entire site and all contents except otherwise noted © Copyright 2001-2010 by Glenn Fleishman. Some images ©2006 Jupiterimages Corporation. All rights reserved. Please contact us for reprint rights. Linking is, of course, free and encouraged.

Powered by
Movable Type

« VIA Rail Adds Wi-Fi to Western Canadian Train Stations | Main | Wee-Fi: Zune for $150, Another WI-Fi Arrest »

August 21, 2007

Wi-Spy Spectrum Analyzers Shows What's in Your Wireless Backyard

To understand what's wreaking havoc on your wireless networks, a spectrum analyzer is key: Sure, you can make guesses. Talk to neighbors. Use Wi-Fi and Bluetooth scanners. But those approaches have limits. What you really need is a spectrum analyzer that can scan the surrounding area across a frequency range and show numerically and graphically what's in the air around you. By moving around with a mobile analyzer, you can pinpoint actual problems, and see displayed over time a moving target as to what's destroying your network's utility.

MetaGeek has two affordable options for desktop Mac OS X, Windows, and Linux analysis, both of which come in the form of a USB stick. When I say affordable, I mean that their units retail for $199 and $399 versus $2,000 and up for full-featured IT management packages and hardware or standalone devices. The two options scan the 2.4 GHz band used for 802.11b/g and one of the bands 802.11n supports. Bluetooth, ZigBee, and cordless phones--among many other devices--also use the band.

The original Wi-Spy debuted over a year ago; the Wi-Spy 2.4x is a more recent entry from June of this year. The differences between the two units were originally software support, with Mac OS X software available just for the original WiSpy at the launch of the newer device. The Wi-Spy 2.4x now has two Mac OS X supporting applications, too, due in part to the programming interface provided by MetaGeek.

MetaGeek has a nice comparison table that explains the difference between the original and 2.4x versions of their product. It boils down to the 2.4x offering greater resolution--it can capture signal strength on a smaller set of frequencies at once--along with higher sensitivity, and an antenna. The antenna can be removed and replaced with others using the same jack style (RP-SMA).

Wispy24I tested both units in my office under Windows Vista and Mac OS X. My office in Seattle's Fremont neighborhood, a mixed retail/office/residential area, has a plethora of Wi-Fi networks. I can see from eight to 14 networks in my office, which is nestled inside a building. I tried turning on a microwave oven adjacent to my office to see what effects that created, too.

Using MetaGeek's own Chanalyzer software, I could watch Bluetooth dancing all over the 2.4 GHz band. Chanalyzer lets you set mark points to track in planar view, in which activity is marked for average and maximum uses across the band, while a live line shows current signal strength. The topgraphic view shows a concentration of activity over time. The spectral view is a moving track that you can replay and change the time dimension on to expand or contract a moment you're viewing. The program lets you "record" a scan, which you can replay in the software. MetaGeek also created a community for sharing scans among those interested in that sort of thing, and has samples you can download and replay in Chanalyzer to show various tests they've performed. (Chanalyzer 2.1 works under Windows. WiSPY-Tools is an independent Linux, BSD, and Mac OS X package with similar features. MetaGeek has a beta of Chanalyzer for Mac that's not currently linked on their Web site.)

Microwave Wispy24The scan above shows the normal environment--fairly congested, and you can see the Bluetooth spikes (by clicking to view the full-size image) as lines that leap up in yellow in the planar view. When I turned on the microwave oven, there was some impact (see at left). In the spectral view, you can see the diagonal green lines between 1 and 2 minutes on the time scale when the microwave was first active; I turned it on again briefly and you can see another set of angry lines. In the topographic view, notice the haze of interference rising above the deeper, thicker red band.

I also experimented with EaKiu, a free and independent Mac OS X software package that supports both the original Wi-Spy, and was updated recently to version 4.0 with Wi-Spy 2.4x support. The package offers some interesting 3D options for visualization, in which you can rotate a continually updating series of receding planes.

I honestly found it tricky to figure out how to test the Wi-Spy models since I had no particular issues facing my rather ugly RF environment at the office, but one fortunately dropped into my lap. Apple recently released its revised model of AirPort Extreme Base Station with Draft N by adding gigabit Ethernet. They also tuned some internal firmware issues to improve speed when network address translation (NAT) was in use. For a review in Macworld magazine, I re-ran the same performance tests that I put the Extreme through in February. In the 5 GHz band, everything was copacetic: terrifically improved speeds due to the gigabit Ethernet removing internal limitations that restricted performance.

Airport Channel Change WispyBut in 2.4 GHz, I was stymied. I could hardly get my N adapters (Intel and Apple) to connect to the base station. With Apple's advice, I turned off Automatic channel selection and chose channel 1. I was seeing kilobits per second throughput when I could connect where I should have seen 30 to 70 Mbps. I fired up the Wi-Spy 2.4x to see what was the matter.

It seemed like I was seeing a lot of energy down at the lower end of the band even when the Extreme wasn't transmitting. I switched to channel 11, and, magically, performance was restored. Now, according to iStumbler, no one is transmitting in channel 1, so there's other ugliness involved. If you look at the Eakiu screen capture (at right), you can see the time sequence moving from newest to oldest on the Z axis (roughly front to back). I switched from channel 1 to 11 right where you see energy levels go down and red (higher dBm signals) disappear on the left, and start to fire up into red on the right. Clearly, something's using that part of the 2.4 GHz band (amateur radio? electronic newsgathering? another licensed purpose? an ugly transmitter?). But without the Wi-Spy, I would have been slightly flummoxed.

The Wi-Spy isn't for every network manager or hobbyist, but it's going to help IT professionals and Wi-Fi busybodies like myself answer a lot of questions that are otherwise lost in the ether.