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Interesting problem for 802.11b networks...

By cvoid in News
Sun Feb 25, 2001 at 03:02:42 AM EST
Tags: News (all tags)

The ARRL has an interesting bit about interference being caused by a wireless network installed in an apartment complex. This is due to the fact that current 2.4Ghz wireless networking gear operates under Part 15, allowing devices to be used in a given band as long as they don't cause interference to licensed users. The FCC has sent a "Notice of Inquiry" to the company that installed the system. This is most likely going to be a very big problem moving forward as wireless networks become more ubiquitous, spectrum is scarce and as most people know, cohabitation of wireless networks and other spectrum users is not at all like running two pairs of Cat 5 next to each other. Read more here.


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Interesting problem for 802.11b networks... | 20 comments (8 topical, 12 editorial, 0 hidden)
Linux WLAN project + Linux WLAN FAQ (3.81 / 11) (#1)
by Dries on Sat Feb 24, 2001 at 02:35:24 AM EST

I maintain a Linux WLAN FAQ for the Linux WLAN project: it is probably a good read and starting point for those willing to know more about IEEE 802.11 (in combination with Linux). The goal of the Linux WLAN project is to develop a complete, standards based, wireless LAN system using the GNU/Linux operating system. What differentiates this project from the Linux wireless extensions and other Linux wireless projects is that we're basing everything on the recently approved IEEE 802.11 standard. More information about the IEEE 802.11 standard or WLANs can be found at:
-- Dries
thanks for the info... (2.50 / 2) (#2)
by cvoid on Sat Feb 24, 2001 at 02:43:32 AM EST

hey good info, thanks. anyone interested in much more experimental wireless digital communications should also check out TAPR.

satellites are cool. especially the ones i control.
[ Parent ]

2 other problems (2.66 / 3) (#4)
by wiredog on Sat Feb 24, 2001 at 08:23:24 AM EST

One is that these devices operate in the same band, IIRC, as microwave ovens. So every time you nuke your dinner, the network goes down. Another is the limited security, which I have rarely seen addressed in reviews of the equipment, which is why I would rather run ethernet.

The idea of a global village is wrong, it's more like a gazillion pub bars.

microwave ovens (4.25 / 4) (#8)
by cvoid on Sat Feb 24, 2001 at 12:06:29 PM EST

you are correct sir. microwaves sit at 2.458Ghz. but yes, they will cause limited interference. the dsss (direct sequence spread spectrum) systems tend to be able to easily work around the noise generated by man made devices such as microwaves, it just won't use the channel if there is sufficient signal or noise present. that is unless the 802.11b card is _in_ the microwave. now _that_ would be a slashdot story.

satellites are cool. especially the ones i control.
[ Parent ]

re: microwave ovens (none / 0) (#20)
by SunDog on Thu Mar 01, 2001 at 09:52:05 AM EST

Your common kitchen microwave oven only operates on the 60 Hz half cycles. The original 802.11b devices were 1Mbps in recognition of this and used the other half-cycle for communication. The newer 802.11b devices operate on both half-cycles, providing 2Mbps, if available, and fallback to 1Mbps as necessary.

[ Parent ]
wave physics (3.00 / 1) (#11)
by Da Unicorn on Sat Feb 24, 2001 at 05:25:46 PM EST

All waves exhibit the ability to propogate sum, difference and multiples of each when 2 signals interract. I'm a bit rusty but I think it is called heterodyning or maybe not. Anyway the more of these devices you get the more of these secondary waves you get all interacting together and although the seconadry waves are weak it can be pretty chaotic locking onto a good signal. And everything you are not looking for is considered noise. Or maybe not.


Wave Physics (none / 0) (#17)
by Bad Harmony on Sat Feb 24, 2001 at 11:26:05 PM EST

I think you are talking about intermodulation distortion, which requires two signals and a non-linear junction, such as an overloaded receiver front end or a corroded electrical connection.

5440' or Fight!
[ Parent ]

frequency hopping? (none / 0) (#19)
by kellan on Wed Feb 28, 2001 at 01:18:47 AM EST

isn't this the sort of problem that fequency hopping is supposed to solve? or am i missing something?

over in corporate land, people are starting to get really excited about the ubiquitious bluetooth devices, but if we are already starting to see interference problems, how can this ever hope to scale?


Interesting problem for 802.11b networks... | 20 comments (8 topical, 12 editorial, 0 hidden)
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