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Use Multiple Channels for Faster Wireless Networking
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.'"
Err... My polish is crap, but unless I am mistaken they seem to have used a 500mW aplifier and a 27dbM antenna to boot.
What's next? Sticking it in the middle of Aresibo and claiming half a light year range?
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
The are actually the same company. (seriously)
I work with a lot of wireless APs and client cards in our lab.
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 office environment, the Linsys G would drop signal after walking past the conference rooms. The Netgear G allowed us to almost walk around the entire floor. I connected a signal booster, and found it to be next to worthless, as it did not improve range. If it did, only by 5 ft or so. It still dropped signal as I walked past the conference rooms.
The measured actual throughput was 4.5mb/s with straight 802.11b, and 21mb/s with the Netgear G.
Quite suprisingly, I had the best results with the Netgear WAB102 Dualband A/B, which is the only A/B AP that uses Atheros second generation A. Tom's Hardware had a write-up on this. Atheros had a whitepaper. I bought 3 of these, and verified the claims.
With a Linksys A+G card, (which uses Atheros 5001X+, as does Netgear WAG511), I got slightly weaker signal strength in my master bedroom 70db), but throughput killed both B and G. I was measuring 24mb/sec throughput in non-turbo mode, and 45mb/sec in turbo mode. In the office, I was able to sustain 7-11mb/sec at the opposite end of the building. The Netgear G was only able to sustain 1-2mb/s. Inside the conf rooms, Linksys G had no signal, Netgear G sustained 7mb/sec, Netgear A in turbo mode sustained 24mb/sec.
In the office, the range of this second generation A actually exceeded that of B, which is something Atheros pointed out in their whitepaper. They said while true A can't go through walls as well as B, the 1st generation A was not performing up to its capabilities. Kind of like how Shannon's law states what is the maximum amount of data that can be carried across wireless, but current technology does not even begin to approach this limit.
I've tested various client cards from Orinoco, to Cisco Aeronet, Prism 2 and Prism 3 cards, and various Atheros based cards. I that the AP affected range more often than the client cards. Though I have found that anything based on the Atmel chipset to be crap. The USB 802.11 card from Linksys (V2.6) uses this chipset. Unfortunately, the Netgear WAB102, uses Atmel for its B, so its B is crap as well. I just use the A portion of it anyways. But the new Netgear triband router, I beleive uses Atheros for all three bands, it just costs an arm and a leg.
The Linksys Triband AP, only uses Atheros for the A, it uses Broadcom for B and G, so its G sucks just like the Linksys B/G stuff.
Somewhere I also read that Linksys will not support any turbo modes in their AP/Routers. (though their A+G client card still supports turbo). Both Atheros and Intersil have planned turbo features. Atheros already had 108mb/s A support in turbo, allowing 45mb/sec throughput by using multiple channels. They already have support for hardware compression, so are promissing a future firmware update that will flip this on, that will allow a turbo mode to sustain 90mb/sec throughput. Its called SuperA. They just released SuperG, which uses multiple B/G channels and compression, to allow 108mb/sec, and I think 45-60mb/sec throughput.
Intersil's turbo technology is called Nitro. Similar (but incompatible) with Atheros's technology.
Are 1,6, and 11 the only channels that don't overlap?
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
INsigNIFICANT
Dlink's AirExtreme G products advertise speeds up to 108 Mbps. Their literature implies that they use two wireless channels to achieve this speed.
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.
Scuttlemonkey is a troll
It's not illegal by the FCC because anything goes in 2.4 GHz so long as you don't go over the power limits... there's no bandwidth-footprint limit that keeps you from using everything between the lines.
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.
Maybe I'm missing something, but could you not achieve the same effect by whacking in two wifi cards and using some loadbalancing scheme in software? I don't see why this would be any slower than a hardware implemented solution, I think the CPU cycles spent are hardly the bottleneck here. Having said that, I think this is a silly solution that only wrecks the whole shared spectrum idea of wifi. If I were a wlan network admin, I would find (packet analyze) and block these guys. (not applicable on public networks ofcourse).
Would a card like this, integrated with airsnort and appropriate drivers allow quicker characterization of the network traffic in an area?
I do security
This is good info to have, Keep in mind if you are trying to impliment wireless in a corporate environment, crappy range is a good thing. I have common problems with Cisco and Symbol AP's having such good range that too many users will pick up the signal in the cube farms of todays corporate america.
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.