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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."
Doesnt the FCC have to approve such item to be for sale in the US market, And part of the approval process is to check to see if the decive interfears with other electronic devices?
30% Troll, 50% Underrated, 10% Interesting
Score:5, Troll
Okay, so what happens when two Super-G networks are within interference distance of each other? Do they both drop down to 54Mbps speed, or what?
Worse than that, Broadcom is likely responsible for using Linux and not releasing their modifications to the source code to those who have purchased the product (a base station) containing the GPLed code. So on top of Broadcom playing a marketing game, we have more reason to hate them.
I suspect that Broadcom's network interface module wasn't written right, and rather than be a complete non-depending piece of code, it depends on something that's been GPLed or is part of the kernel itself, and that would mean that it too would have to be GPL. If it is GPLed, then Broadcom would be releasing specifications on their devices that they don't want us to have, and we wouldn't have to pay for the base station anymore, just for the card...
Do not look into laser with remaining eye.
Don't you just love the joys of unregulated spectrum usage? If someone can get 108Mbps out of thier wireless by using more spectrum, I say let them do it. As long as its within power regulations, I can fine tune my wireless around it. If I get really upset I suppose I can buy one of the super-g systems for myself.
When the FCC sais that anyone can use this swath of the spectrum for anything within these power levels, and someone makes a gadget that does so, people have no right to complain if it interfears with thier gadget.
Karma: SELECT `karma` FROM `users` WHERE `userid`=138474;
IIRC, the only regulations for those frequencies are power restrictions. Beyond that, you can do whatever you want. Even if it breaks everything else.
It may be that the FCC would consider two seperate broadcasts can only use half the power each, but I kind of doubt it.
autopr0n is like, down and stuff.
So what!? It's unlicensed spectrum and they can do with it what they wish as long as they don't violate any FCC rules, which Atheros is clearly not.
Part 15 devices must accept any interference, including that which may cause undesired operation.
I'd personally like to see point-to-point 2.4GHz hardware that uses the ENTIRE spectrum for extremely high bandwidth applications... that'd be very cool
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
Broadcom *do* produce OSS drivers - just not for their 11g stuff. I'm told that's due to patents (not sure how true that is, though).
They also released the source to their DOS configuration utility to their network cards (the files had 'copyright broadcom' and 'not for redistribution' written on them, however).
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?
With 12 more channels as of this past week, why would one fight over the crowded 2.4 GHz band? Unless one doesn't have a product for the less crowded 5 GHz band.
Your post ist not Insighful, but Clueless. So you say almost everything is GPL'ed. Yes, exactly, with the totally small exception of the COMPLETE hardware abstraction layer. Yes, everything which deals with the hardware is binary only and NOT gpl'd. The rest of the driver is worthless, the heart and core would be the HAL. So this driver is better than nothing but not really acceptable.
Atheros is as bad as Broadcom is. Dump both and buy Intersil PrismGT. Not even did they support a linux driver effort, they even sponsored the developent!
Yeah and only three of them can be used simultaneously without any interference. Basically any given channel will overlap with the four neighbouring channels(two in both directions).
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
All of the above!
First, there's fundamental thermodynamic/information theoretical limits on the amount of information that can be carried in a given amount of spectrum for a given number of symbol values. This is because any "modulation" of a carrier causes the carrier to have spectral products off the carrier frequency. Modulating the carrier at faster rates makes the overall signal wider. I could go deep into sampling theory here but I won't.
The wider a signal in spectrum, the more noise there is over that spectrum, and the more power must be spread over that spectrum to be detectable over the noise floor.
Maximum Theoretical Throughput in BPS = Bandwidth * Log2 (S/N+1)
Where S is the signal strength and N is the total amount of noise in the signal bandwidth. Note that N increases linearly with bandwidth in typical RF applications.
Frequency also matters because the amount of noise present on different parts of the spectrum varies. Almost all noise above 100MHz, though, is created either thermally inside the receiver.. or comes from man-made sources.
Oh, yah, I forgot to discuss C.
All the consumer 802.11* products today are half duplex. That is, they can't transmit at the same time they're receiving, and only one party can talk at a time while still allowing the signal to be demodulated successfully. (Vivato is doing some really neat work with phased arrays to receive from multiple people at once, but that is high-end $10K+ hardware).
Channel arbitration, or deciding who can talk when, is expensive, and isn't perfect. A certain amount of the time, two wireless transmitters will decide to talk at the same time.
802.11 uses a CSMA/CA protocol to prevent this "doubling". CS is Carrier Sense-- side A can tell when the other side is transmitting.. but in this case usually only when side A is not transmitting itself. MA indicates that it is a multiple access channel. CA=collision avoidance specifies that a protocol is involved where one side transmits for a little while, and then stops and checks to make sure there's no one else transmitting.
The amount of time needed to spend on the test carrier is related to the propagation delay between stations-- in other words the speed of light and distance, as well as the switching times from transmit/receive and the amount of listening time necessary to determine if someone else is transmitting, as well as various other probablistic answers (the odds of someone else both starting to transmit and also checking for someone else at the same time, for instance-- adjusted for propagation delay, of course).
All of this arbitration, waiting, etc, wastes bandwidth, and thus lowers real world throughput.
What limits throughput on a wireless connection? Is it broadcast power, frequency, amount of spectrum, or "c"?
All of the above!
The most limiting factor is the amount of spectrum -- the bandwidth allocated to the signal. If you're restricted to a very narrow set of frequencies, you can't send as much data in a given amount of time.
But, once you've picked the bandwidth to use, broadcast power and frequency each affect how well the transmitted signal can be received. Lower frequencies pass through solid objects more easily, for example, but often require more broadcast power. There are myriad details affecting the quality of a signal as it passes from the transmitter to the receiver, not the least of which is interference from other transmitters.
And finally, "c" ultimately affects the latency of your signals. NASA's conversations with the Voyager spacecraft would be an extreme example: it takes about 25 hours now for a signal to make a round trip from Earth to Voyager 1 and back. Closer to home, even Earth satellites are far enough away that the speed of light becomes a limitation -- the round trip to a geosynchronous satellite is 0.239 seconds. If your signal is mostly one-way, this has very little impact. Television, for example, isn't hindered by this. But any kind of interactive connection like online gaming or even telephone conversations are adversely affected by that amount of latency.
I still think that the emerging spread spectrum technologies are our best bet for wireless computer networking.
- Peter
INsigNIFICANT
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.
If you look at the radiation pattern for Wi-Fi (or any spread spectrum) it has signal concentrated over a range, but there are harmonics and side lobes and out of band leakage -- it has to be within certain tolerances, but it's allowable. So if you're centered on channels 5 and 6, there will be slop into 1 and 11, but most devices are designed to have the smallest amount of slop.
Freelance tech journalist for the Economist, MIT Technology Review, Macworld, and others
If you place Adtran Tracers anywhere near an 802.11b cell the effect is rather like sandblasting a soup cracker. The Tracers split the band with one end using the lower half and the other using the upper. They bridge ESF T1 frames so their utilization of spectrum is always 100% whether they're idle or not.
Broadcom is just producing either a concatenated 108 mbits by using two channels at once or they're producing a full duplex 54 mbit 802.11g connection.
The FCC will not do anything about this sort of thing. As an unlicensed band user they'd prefer that you just drop dead.
Unlicensed band may work well in unpolluted rural areas with one carrier but in metro areas it is pretty much a disaster in the ISM band and the same troubles are starting to happen in the UNI (5.8) band as well.
If your business plan depends on flawless throughput in the ISM band please send me your home address - I'll come over, kick your ass in your driveway, steal a bunch of stuff from your house, and we'll call it good - the financial effects and suffering are the same but you get it all compressed into a few short minutes of fun, instead of spending a year of your life flushing your money along with investor's dollars.
I am very easy to get along with, but I don't have time to waste being nice to people who are being stupid. -Theo
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"Ah, fuck, my pacemaker!"
-- thinkyhead software and media
Stock antennas are pretty unimpressive and leave a lot of room for improvement.
Antennas are cheap, especially if you build your own, and they don't burn up battery power.
Antennas work in two directions. An antenna with a better pattern improves your range for both transmit and receive. An amplifier on one side of a link doesn't help you hear the other side any better.
Antennas with radiation patterns that match where you need the network reduce interference coming in as well as interference going out.
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