Use Multiple Channels for Faster Wireless Networking 166
icypyr0 writes "The Register reports: 'Current dual-mode 802.11 'a' and 'b' access points use only one of Wi-Fi's 11 RF channels at a time, with users taking turns. The Engim chipset can 'see' all 11 at once, and can use the three non-overlapping ones (1, 6 and 11) in parallel, increasing total throughput and enabling features to be incorporated in silicon that are usually implemented, at extra cost and performance degradation, in software.'"
overlap? (Score:4, Insightful)
Re:overlap? (Score:5, Informative)
Translation: They're covering the entire 2.4 GHz band, and making no appoligies to anybody else who hoped to use it near their systems. Any 2.4 GHz phones will have nowhere to hide.
Re:overlap? (Score:3)
Re:overlap? (Score:3, Interesting)
You could use a spectrum analyzer to monitor 2.4GHz band to see if anyone in your neighbourhood is using it.
Jeroen
Re:overlap? (Score:3, Informative)
Trial and error it is...
Re:overlap? (Score:3, Informative)
Maybe I'm missing what you're getting at, but the 802.11b definitions for channels aren't used by anything else, but the spectrums that they cover are still unregulated... which means that anything can use it.
Now if you're saying that you can't see those with a 802.11 aware device then yeah, but if I made some device that just broadcast randomness on the 2.4-2.5ghz range then that would interfere with all of those channels. It's also interesting to note that these ranges differ depending on the country. J
Re:overlap? (Score:2)
Re:overlap? (Score:2)
The best solution is to move to 5 Ghz. (802.11a), which has 13 non-overlapping channels. But this has a slightly shorter range, and chips are still slightly more expensive.
Re:overlap? (Score:2, Insightful)
Re:overlap? (Score:3, Insightful)
If you really push it you can use smaller spacings such as three or four channels instead of six.
Jeroen
Re:overlap? (Score:3, Informative)
-matthew
Re:overlap? (Score:3, Interesting)
We have 1 to 13 here in the Netherlands.
(Besides its not that hard to use all fourteen)
Jeroen
Re:overlap? (Score:3, Informative)
--
Retail Retreat [retailretreat.com]
Re:overlap? (Score:5, Interesting)
You can get away with using four without much problem. I use 1, 4, 8, 11 for my wide-area 802.11b network.
You have to plan out in 3 dimensions when you have multiple access points like that. Often the strongest signal available to a roaming user is above or below them, rather than on their floor.
With only 3 channels available, it's too hard to map them out. With 4 you can at least guarantee that no two adjacent access points are on the same channel.
- Peter
Re:overlap? (Score:2, Interesting)
Is this a consequence of the four-color theorem? It sounds distantly related.
Re:overlap? (Score:3, Interesting)
More throughput... but... (Score:3, Insightful)
What about 802.11G? (Score:1)
Simon.
Re:What about 802.11G? (Score:3, Informative)
Actually, no. A wired network provides a dedicated connection, while a wireless provides a shared one. This is basically the difference between 10baseT and 10base2. The shared connection (wireless and base2) will have to deal with collissions and will yield about 20-30% max load (depending on the kind of traffic). This is why your G network will only yield 11Mbps and not the full 54Mbps. Your 100baseT network will
Re:What about 802.11G? (Score:2)
However all ethernet standards 10baseT, 10base2, and also 100baseT are shared.... thats why they have things like collisions.
You can give it the appearance of a dedicated network by using routers instead of dumb hubs.
Jeroen
Re:What about 802.11G? (Score:2)
Oh, and 1000baseTX is a switched-only Ethernet(Of course, it's only really ethernet due to marketing decisions).
Re:What about 802.11G? (Score:3, Insightful)
Re:What about 802.11G? (Score:3, Informative)
Re:What about 802.11G? (Score:2)
However you are correct that 100baseTX will blow away 802.11g anyday even in a hub-based topology(In fact, with a properly designed network, switched full-duplex 10baseT will outperform 802.11g)
Re:What about 802.11G? (Score:4, Insightful)
Whether wireless will work quite this well, I don't know.
Re:What about 802.11G? (Score:2)
With the CSMA/CD the rates went up to the 90s
Re:What about 802.11G? (Score:3, Informative)
In fact a switched 10baseT network will perform about as well as an 802.11g network, and possibly better if you can run all of your systems in Full-Duplex mode (Not a given for 10baseT hardware)
Re:What about 802.11G? (Score:2)
So, you actually are getting 5+ Megabytes per second transfer rates out of 802.11g? Unless you have only one AP and one client, I call Bullshit.
Tragedy of the commons forming! (Score:5, Insightful)
Re:Tragedy of the commons forming! (Score:5, Informative)
It gets better during the summer when a lot of the students around me leave and shut off their APs.
Re:Tragedy of the commons forming! (Score:5, Insightful)
Re:Tragedy of the commons forming! (Score:2)
Probably, soon everyone needs such a card to shout loud enough between all the other people in your neighbourhood who have already such a thing.
If the cards are smart enough to not completely cease to work if there is a wifi traffic jam - if they scale back on the number of channels occupied, everything should be ok(?)
Re:Tragedy of the commons forming! (Score:2, Interesting)
i live in a tightly populated suburban area and i can see 8 or 10 APs immeditately around my home using simple tools like netstumbler. this doesn't count APs that don't announce their SSID, as well as who-knows-how-many 2.4ghz cordless phones.
my 2.4ghz cordless phones get interference all the time from what i can only assume are everyone elses APs and phones around me.
simultaneous multiple channel use is a bad idea, unless you are out-of-range of others...
Re:Tragedy of the commons forming! (Score:2)
Re:Tragedy of the commons forming! (Score:2)
Well, if you use it all the time (which is rare) then thats true with current APs.
However, that's not necessarily true of future APs though. There's no reason why an AP can't use a directional aerial (e.g. phased array) to ignore the other APs and users, and then everyone can use the same frequencies.
Re:Tragedy of the commons forming! (Score:2)
This could really speed it up when using directional equipment.
Re:Tragedy of the commons forming! (Score:3, Informative)
For directionality to work, it requires widely spaced antennas (many meters), and this allows far more discrimination than your aerial.
Overlap explained (Score:4, Informative)
if you've ever tried actually haveing 11 acess points on different channels you'll notice massive interfearence
Re:Overlap explained (Score:3, Informative)
Not quite. (Score:5, Informative)
You can read this [extremetech.com] for a little more info.
Quite not quite (Score:4, Informative)
Your nyquist analogy assumes a simple binary symbol set (ie. "1" and "0"). The signal bandwidth is a function of the symbol rate. If your symbol set is larger than just two symbols (say 8, or 16, or ...), then you can deliver more bits per symbol. That's why "G" delivers more data bandwidth than "B" in the confines of the same channel signal bandwidth.
-rickFirmware (Score:1)
No way (Score:2)
Re:No way (Score:2)
Most cards can link to at least three cards
Use 3 connections between them and triple the throughput simple. Should work problems asociated with massive throughput aside should work well.
My friend's network goes out when he receives a phonecall course he has a linksys router
Re:Firmware (Score:2, Interesting)
You would only need a hardware upgrade if you wanted each client to be able to make use of multiple channels simultaneously and reach that 50Mbps throughput figure quoted in the article.
Otherwise it's a solution for reducing bandwidth contention in heavily trafficked networks (and protecting 802.11g users from bandwidth degradation by 802.11b clients, as ment
As if Wi-Fi space wasn't crowded enough already... (Score:4, Insightful)
-matthew
Re:As if Wi-Fi space wasn't crowded enough already (Score:5, Funny)
Well, it's kinda handy when you don't want any, ah, wires.
Re:As if Wi-Fi space wasn't crowded enough already (Score:3, Insightful)
Re:As if Wi-Fi space wasn't crowded enough already (Score:3, Informative)
Re:As if Wi-Fi space wasn't crowded enough already (Score:3, Funny)
Except that .11 is cheap and easy to get/ impliment while bluetooth is almost nonexistant.
Re:As if Wi-Fi space wasn't crowded enough already (Score:2)
Re:As if Wi-Fi space wasn't crowded enough already (Score:2)
(not that you should be relying on wireless at all, but that is a different story)
no trimode? (Score:3, Interesting)
but it's a good idea.
Hopefully, other chipset makers (TI, etc.) follow suit, which in turn will reduce costs (thx to competition).
Of course, if it can do all three, 'b', 'a', 'g' separately, and each with the parallel-ness, that would kick ass.
Re:no trimode? (Score:2)
Re:no trimode? (Score:2)
Overlap affects B and G, Not A or H (Score:2, Informative)
802.11g => ~32Mbps throughtput x 3 non-overlapping channels = ~90Mbps total usable bandwidth
802.11a => ~25Mbps throughput x 12 non-overlapping channels = ~300Mbps total usable bandwidth
802.11h => ~25Mbps throughput x 24 non-overlapping channels (due to better pwr mgmt) = ~600Mbps total usable bandwidth
Re:Overlap affects B and G, Not A or H (Score:2)
Warning: Embrace and Extend logic detected (Score:2, Redundant)
It's known that mixing 802.11b and 802.11g on the same network causes slowdowns... their effective solution is to put the 802.11b devices on a different channel a
Some comparrisons regarding G (Score:1, Informative)
If you are talking about G type stuff, stay away from Linksys, they have the crappiest range. When I used it in my house, I would get 68db with an Intel 802.11b AP, but the Linksys G router/AP yielded 77db, and that was only going through 2 walls.
I replaced it with a Netgear WGR614, which uses the Intersil Prism GT chipset (as does the D-Link we tested), and got much better range. Similar to straight B. ~68 or 69 db in my master bedroom.
In our
Re:Some comparrisons regarding G (Score:5, Interesting)
I try to place my AP's so that 25 users will access them from there desks or conference room. Some conference rooms that are very large I will place 2 or 3 AP's on different channels with the power turned all of the way down so it will balance the user load between the them.
Since there are only 3 non overlaping channels it is often a chore to design wireless in a room where the same channels dont overlap with each other. Poor range solves this problem. Think of how to put 5 AP's in a room with 3 channels, it can be done, poor range is the key.
We urge our users to use their wired connection and use their wireless when in meetings or on the road at other corporate offices.
Re:Some comparrisons regarding G (Score:3, Insightful)
This is a great example of an intelligent use of the 802.11X protocols. Use only as much power as you need, and only where needed. As opposed to the usual (and wrong) tactic of using full-power in an attempt to squash a neighboring access point's signal.
-rickRe:Some comparrisons regarding G (Score:2)
Are the output power the same on both of the cards/AP's you tested?
Re:Some comparrisons regarding G (Score:3, Informative)
Somewhere I also read that Linksys will not support any turbo modes in their AP/Routers
Linksys is supporting a "turbo" mode, thanks to Broadcom's "Afterburner" technology, which is implemented as Linksys's "SpeedBooster" technology. Afterburner requires a new revision of Broadcom's 802.11g chipset, however, so previous G products can't be enhanced, only new products.
Atheros already had 108mb/s A support in turbo, allowing 45mb/sec thr
Interference (Score:3, Insightful)
I consciously decided against buying something like this for that very reason when I bought my wireless hardware, even though the cost difference was negligible.
Yeah! Screw the neighbors! (Score:3, Funny)
Re:Yeah! Screw the neighbors! (Score:2)
Any time a band is released for consumer applications, this almost always happens... somebody tries an application that uses all of it. Eventually, those devices are shunned by the marketplace when they're blamed for causing everything else on the same band not to work...
Re:Yeah! Screw the neighbors! (Score:2, Funny)
Re:Yeah! Screw the neighbors! (Score:2)
Limit the transmit range (Score:1)
Fah. Not worth it. (Score:2, Redundant)
This is going to casue more problems in resedential areas than it will solve.
Valid Uses (Score:3, Insightful)
Large old office buildings that arn't wired for ethernet, large warehouses, and people who live on large plots of land.
Yes, if you are living in a typical burb or in the city and try to use one of these you could run into issues with running out of channels. However not everyone lives/works in small areas.
Re:Valid Uses (Score:3, Interesting)
Common bond: Areas where for the range of WiFi, you control nearlly all of the territory. Therefore, you're sure you're not getting in the way of anybody else because there's nobody else arround.
A densely packed dorm or appartment house is not the place to do that. It's to the point that in 2-family dwellings, the families need to agree on a consumer bandwidth sharing plan between each o
Re:Valid Uses (Score:2)
The more people you have on the network, the more of an issue available bandwidth will be. Everyone getting their own dedicated 100mbps wire is better than dozens sharing 108mbps common wireless bandwidth.
It only costed me about $100 worth of materials to connect two computers 140ft away from a switch, and a third one about 50 ft away from same switch. The cost counts metal conduit, metal b
Sounds like (Score:3, Insightful)
If it isn't actually illegal, it's certainly anti-social. But then again, I don't use any wireless kit anyway
Re:Sounds like (Score:2)
However, this does violate the IEEE specs for 802.11b and 802.11g. They can claim that they can interoperate with such devices, but they aren't one themselves. Those specs say one channel to a customer so that other applications and networks can exist without being blown off the air.
Two 801.11g networks nex
Re:Sounds like (Score:4, Interesting)
So if my neighbors get one of these I just need something that will broadcast random noise at the maximum allowable power level over the whole 2.4Ghz band, with a directional antenna. Then we'll see how long it takes for them to give up and take it back to the store because it doesn't work.
Huh? (Score:2, Insightful)
What they are really talking about (Score:5, Informative)
Based on the article the chipset will be *capable* of using all 3 non-overlapping 2.4Ghz ISM channels. That will allow the associated users to be split across the 3 channels rather than all on a single channel and competing for access to the channel.
The same tradeoffs that drive WLAN design today will still exist. Its not a panacea, but it does add new possibilities to the engineer's set of available solutions.
By opening up the front end of the radio they can look at the whole band and do some very interesting noise reduction techniques. This is alluded to in the article, but I think its the most promising part of the chipset. The ability to identify and reduce the affects of wideband noise will got a long way to improving reception of WLAN signals....
tradeoff (Score:3, Interesting)
Re:tradeoff (Score:2)
Re:tradeoff (Score:2)
Re:tradeoff (Score:3, Insightful)
IOW, yo
Re:tradeoff (Score:2)
Did anyone else first read the headline... (Score:2)
I can see the FCC loving this. (Score:3, Interesting)
Dlink has a similar idea (Score:4, Interesting)
I have their wireless card & router, but can't get the 108 speed because of some legacy b adapters in the network. The G speeds are quite nice - even though 802.11b's theoretical speed is higher than my DSL bandwidth, it's actual performance was quite dissapointing.
Re:Dlink has a similar idea (Score:2)
same effect using two wifi cards? (Score:3, Interesting)
scanning networks (Score:4, Interesting)
Misunderstanding of Engim (Score:5, Informative)
As a result, if you're in a big company, and set up 3 off-the-shelf 802.11b access points, on 3 different theoretically non-overlapping bands, you'll still get something on the order of, maybe, 1.6x the bandwidth you'd get with one.
What Engim does is it has an insanely fast ADC/DAC front-end, that grabs the entire 802.11b/g spectrum, including all the bands. Then, they have a fancy DSP that looks at the bands together, figures out how they interfere with each other, and sorts them out. As a result, in a theoretical world, where only notebooks were transmitting to the access point, they would have 3x the bandwidth. They do fancy transmitting techniques, so that notebooks on all 3 bands can hear at the same time. So if the wireless access point was transmitting, and all the notebooks receiving, they would, again, have 3x the bandwidth.
The problem is that notebooks don't have this sort of technology, so when they transmit, they cause interference for other notebooks. If the Engim WAP transmits on band 1 to notebook A, and notebook B transmits on band 2 at the same time, the transmission from notebook B may interfere with that from the WAP. As a result, in practice, it's a little less than 3x the bandwidth, but not a heck of a lot less. They try to juggle notebooks between bands, based on location, so this doesn't happen, but it doesn't really work too well.
The technology they have is wicked cool, actually. For those worrying about interference -- it's really not a problem. First of all, this isn't for personal WAPs, but for $1000 access points you'd see on an IBM or Microsoft campus. They won't be going in apartments any time soon. You need a minimum of 3 very expensive chips for a single WAP (RF front-end, ADC/DAC, and DSP). Those places don't tolorate employees setting up their own WAPs anyways.
Second, you still have the remaining bands. The way 802.11 works, with the interference issues described above, if I set up a WAP, and my neighbor sets up a WAP, we will be interfering. We'll both have wireless networks, but both with reduced bandwidth. You can still set up your own WAP on any of the remaining bands, and it'll work -- it's just that if you try to send a packet at the same moment as the Engim network, you'll get a collision and retransmit. This is what happens anyways. 802.11 was never designed to have many, non-interfering bands. It was designed to have many, interfering, overlapping networks, with packet collisions. By design, the total bandwidth of 5 overlapping networks, in the same area, is the same as if there was only one. Each network gets 1/5 of the bandwidth then. This is the exact issue Engim technology is meant to address.
In terms of cell phones, etc. my impression is that the Engim technology was actually smart enough to look for "interference sources" and try to pick bands around them. This last bit is from an Engim PowerPoint slide, so I'm not sure if it's actually implemented or vaporware.
Noooooooooo! (Score:4, Insightful)
I already have only -2- channels that I can reliably use in my house without interference. Every other channel is in use for ISP access in our community or gets interference from cordless phones and microwaves.
If you want more throughput, use different frequencies. Even if they are close to 802.11b/g that is better than going into the already established spectrum.
Yes, I know that this is not mandated or regulated space, so there is not much I can do to enforce my needs. However unregulated waves only work if people make an effort to play well together.
Re:Noooooooooo! (Score:2)
I've got a scanner that receives up in the 2.4GHz range, and I've swept thru it a couple of times looking for signal while my microwave was operating - not a peep, even at 3 inches away.
Bye Bye Spectrum (Score:2)
that's right now we don't have ANY spectrum left because joe smith, mary smith, and dan smith (who are all my neighbors) are using their 3 channeled access points at the same time to download music off kazaa and I'm left with no good open channels.. woohoo! great management!
Ancient News (Score:2)
http://www.extremetech.com/print_article/0,1583
Oh, and of course, the real world reason this isn't such a hot idea is that you can only use multiple channels to boost bandwidth only in WLAN environments where you control where the APs go so you don't have multiple APs interferring with each other.
Steven
No (Score:2)
Re:Frequency band to be reorganized? (Score:3, Informative)
Re:Use Multiple Channels (Score:2, Insightful)
Re:ummmm. (Score:3, Funny)
Re:Department (Score:3, Interesting)
Re:Department (Score:3, Insightful)