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Broadcom Accuses Atheros Of WiFi Pollution
eggboard writes "We just posted a story at PC World about 802.11g chipmaker Broadcom's claims that the high-speed 108 Mbps mode available in rival Atheros's AR5004G chipset disrupts all nearby Wi-Fi networks. The Turbo mode, part of Atheros Super G, uses two Wi-Fi channels (5 and 6) to double bandwidth, but Broadcom says this can lead to 'an enormous degradation in the speed of nearby 802.11b and 802.11g networks.'. D-Link and NetGear are shipping Super G-based devices. If Broadcom is right, Atheros gear would pollute neighbors' networks. If wrong, they're putting out a pretty heavy marketing smokescreen just before Comdex - where Broadcom says they'll be demonstrating the Atheros problem."
Having been bothered enough by my question I went and looked it up. I first looked at a walkie-talkie i had and Read the following "This Device complies with part 15 of the FCC rules. Operation is subject to the condition that this device does not cause harmful interference."
Then looking up Part 15 of FCC Rules available HERE. I focused in on 15.5 General conditions of operation.
Which states
TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
PART 15--RADIO FREQUENCY DEVICES--Table of Contents
Subpart A--General
Sec. 15.5 General conditions of operation.
(a) Persons operating intentional or unintentional radiators shall not be deemed to have any vested or recognizable right to continued use of any given frequency by virtue of prior registration or certification of equipment, or, for power line carrier systems, on the basis of prior notification of use pursuant to Sec. 90.63(g) of this chapter.
(b) Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, cientific and medical (ISM) equipment, or by an incidental radiator.
(c) The operator of a radio frequency device shall be required to cease operating the device upon notification by a Commission representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected.
(d) Intentional radiators that produce Class B emissions (damped wave) are prohibited.
30% Troll, 50% Underrated, 10% Interesting
Score:5, Troll
Not really, the 2.4Ghz spectrum that the .11b and .11g protocols use is an ISM band which is basically the FCC's term for junk spectrum that can be used for virtually anything. This is unliscensed space and the rules are pretty lax. So long as you aren't exceeding power requirements and aren't bleeding into adjacent frequency spaces you are pretty much ok. The frequency seperations used in .11b and .11g are IEEE standards not FCC ones.
.11b channel ganging tech. Not only were they using two channels but their side interference in that mode went from bad in their normal mode to absolutely atrocious in the "turbo" mode.
That being said we observed this with Atheros's
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
Alot of gear operating in the 2.4GHz area uses the _whole spectrum_. Western Mux (Proxim?) makes Wireless T1 gear which seems to be very popular for backhauling traffic from Cellular sites. Power output is regulated, but not spectral efficiency.
Abstainer: a weak person who yields to the temptation of denying himself a pleasure.
--Ambrose Bierce
I live on a suburb with several (20+) radiomodem access points - no cables, no ground lines, just several "clusters of houses" hooked to their antennas. Connections to several ISPs.
The network connection sucks.
At first it worked fine. I'd say it worked great. People heard it works great so they began installing the equipment themselves. The lines began disturbing each other, but it still worked okay. More people installed this, and the network quality began to suck really. So some of them, to overcome the noise, installed signal amplifiers for their antennas. Result? Everyone without amplifiers simply lost their connections completely. So people began installing amplifiers en masse, which resulted in that connection sucks for everyone again. My packet loss ranges from 10 to 60%. TV signal gets disturbed. Radio mice and keyboars don't work. Great, just great. And the ISPs just can't come to agreement on putting one, good, shared ground line.
Ether is a limited resource and wireless in larger amounts will suck, no matter what.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
I don't know about Atheros, but ever since my 2-floors-down-neighbor put up a D-link "b" access point, I can't connect to my bedroom (g) access point from my own living room, even though I've separated the channels (2 and 11). I am forced to connect to his.
Does anybody test for interference with these damn things?
Normally I'm inclined to agree, but not in this case. Having worked for companies that have dealt with Broadcom, and talking to some of their engineers myself, I know a bit about the company itself.
Their engineers are very smart people (most of them hold degrees above the typical Bachelor of Science), and I've seen their source code (for cable modems), and it's well written. Their spec sheets (again, for their cable modem products) are generally top-notch, although I'm a bit miffed at them about the whole Broadcom 3415 tuner chip issue (with the patent infringement suit against Microtune), and the whole Linksys/Cisco situation. I'm also not keen on their interview processes either (myself and a couple of my former co-workers have all interviewed there in the past), but that's not related to this issue.
That aside, I'll address the statement from you that I copy/pasted... If the hardware sucks, having GPL'd drivers for it is of no use (at least not to me). If the Atheros chipset is causing interference (and I reserve my judgement until I hear more about the issue), then as far as I'm concerned, I'd rather buy other hardware that actually works.
-- Joe
Yeah but look at part (b). You also must accept interference. Two people with Part 15 devices that interfere with each other have to work it out between themselves. The FCC only gets involved if a Part 15 device is interfering with licensed users, like hamradio, police radar, TV, commercial radio, etc.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
Part of living in a harmonious society involves cooperating with others to ensure what you're doing does not impair the freedom of others. This, at a very high level, is one of the reasons why we go around inventing protocols - clear, agreed-upon, protocols ensure that everyone can benefit from a technology rather than whoever has the most costly design.
There's a difference between what's legal, and what's right. Damaging the ability of others to use an established technology for minor bandwidth gains on your part is a Tech-world example of what may be legal but what most certainly isn't a decent thing to do.
You are not alone. This is not normal. None of this is normal.
The 2.4GHz unlicensed band has 3 non-overlapping channels (1, 6 and 11). You can use up to three DSSS (Direct Sequence Spread Spectrum) devices in the same location without them interfering with one another to a great extent. This would include one or more Wi-Fi networks, 2.4GHz cordless phones (that use DSSS, not FHSS), Baby Monitor, etc.
Anytime you have more than three devices co-located some of them are going to interfere with one another. That interference is going to either degrade your connection speed or it's going to prevent you from being able to connect all together.
If this 108Mbps technology is truly setup to use channel 5 and 6, then Broadcom is right. It is going to interfere with 2/3's of the available non-overlapping channels.
On a quick side note, because wireless connections do not have collision detection, they have to rely on collision avoidance. Once a packet is sent the receiving station has to reply with a receipt acknowledgement before more data is sent, this basically works to cut the actual data transfer rate in half, not that it matters anyway, since almost all wireless networks are used for internet access from ISP's that are lucky to break 3Mbps.
Back to my point though...if you have a wireless network, then be a conscientious wireless user and keep to channels 1, 6 or 11. You can also use the site survey software that came with your wireless adapters to find out what channel other nearby users have occupied already so you can avoid those. Additionally, if you buy other wireless products, avoid the 2.4GHz band if you can. If you must get a 2.4GHz cordless phone or baby monitor then do your homework and strictly avoid those devices which use FHSS (Frequency Hopping Spread Spectrum) - they are frequency hogs which have a tendency to kill other wireless devices.
Craenor - Senior Wireless Networking Specialist for Dell, Inc.
Mesh networks offer the possability of having each node pass a note to the node closest to them in the direction of the node they are trying to reach. They only have to speak loud enough for that closest node to hear, making meshes a lot more scalable. Like passing notes in high school rather than shouting across the room and getting the teacher pissed off at you. :)
I suspect that as wireless devices become more popular we'll need something like mesh networks to make more efficient use of the spectrum. In fact, in a manner similar to Bittorrent and Freenet, the more people that participate in a mesh network, the more resiliant and speedy the whole network is.
sb