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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.'"
or 66 miles for the math impaired (sigh). Still, that's rad! You could access that across the English channel!
stuff |
FYI,
google calculator says its something like:
110 kilometers = 68.3508311 miles
Hey - that antenna they're using looks a lot like the one from this story. Of course, he only claims a LOS range of 10 Miles.
666-607: 6th floor apartment of the beast
Anyone got a Polish->English translator?
I checked Google, Babblefish & Dictionary.com with no luck.
Good security is based upon reality and common sense. Common sense is a function of having common knowledge.
So this is a relatively cheap method to get Internet access in distant locations, specifically in mountains, where it is difficult to get a wire.
Regards
The article claims the experiment used off-the-shelf, commercially available, unmodified components (1.1m / 3.5ft parabolic antenna and a 500mW amplifier). Experiment was conducted in a mountainous region in southwestern Poland.
:)
So this isn't all that bad... considering the average laptop wireless card puts out, what, 20mW? 50mW? using a 500mW amp to achieve a much greater distance is pretty sweet. By comparison, the article quotes a Swedish experiment which used stratospheric baloons and a 6W amp, but they don't mention the distance achieved.
Mind you, rules about how much power certain appliances / transmitters can put out with or without a permit vary across the globe, and I'm not sure whether 500mW is legal for private unlicensed use in Poland or not. But if it is, more power to them.
Now, where can I get mine??
Have EVDO, will travel.
Here
is the story from July of an outfit getting 310km using WiFi from ground to a balloon. This was done by Alvarion and the Swedish Space Corporation and acknowledged by Guinness (as in world records not as in beer).
105 km is a good ways off. But Amateur Radio operators have been getting better than this with their voice transmissions (and possibly digital) on frequencies from 50 MHz to 10 GHz at the 2003 September VHF QSO Party.
See some of their setups at http://www.arrl.org/contests/soapbox/?con_id=53.
Our university station was making contacts on frequencies greater than 2.4 GHz for distances longer than 200 miles. Contrary to common sense, Line-of-Sight is not necessarily required to get microwave transmissions to work over long distances. But they're very weak ;-)
The article already is almost dead... Can't check how they did it, BUT... the biggest problem isn't signal power, that part is easy with even a minimal amp and decent parabolic grid antenna. The tough part is the curvature of the earth. Beyond 10 miles or so, you have to get your antennas substantially off the ground, otherwise the amps and high gain antennas make absolutely no difference...
or not?.
There isn't much to block a radio signal if you're in a balloon; so the news that Alvarion has managed to reach a 310 km distance probably isn't as exciting as it sounds.
Note to self: get smarter troll to guard door.
I did a 21.7 mile shot using Cisco Aironet BR342, Andrew 19dB solid dishes, and YDI
500 mw amps.
I'm a bit embarrased to admit using a wireless LAN product for backhaul work, but some morons overtightened
the patch cable on an Andrew P2F 5.2-5.8 GHz 2' dish hooked to a WiLan AWE-120 5.8 GHz radio and put their link out
of service.
Despite extensive tweaking the link never managed more than analog modem speeds. It helped in recomissioning the UNI band stuff, but was otherwise
useless for hauling traffic.
802.11[bag] is NOT an access product. Take a look at Alvarion's Breeze Access II, or better yet just wait for an
802.16 product meant to do access work.
802.11[bag] is NOT a mobile access product. That market belongs to licensed band products with ISDN like performance offered by cellular companies.
Anecdotal evidence of mobile access to one police department in a town of 12,000 does not equal proof of concept for operation in urban areas; its plain
dumb luck coupled with no competing ISM band ISP(yet).
802.11[bag] is NOT a backhaul product. Backhaul radios are made by WiLan, Redline, Aperto, Proxim, and others. The minimum cost is $2,500 an end just for
the radio, most of them are in the UNI band, the full duplex products are generally split band 5.2/5.7 GHz, and they provide typically eight to ten
mbits for entry level products, unlike 802.11b which NEVER, EVER gets 11 mbits in long shots, with 1 or 2 mbits being the typical rate.
802.11[bag] SHOULD NOT BE DEPLOYED BY MONKEYS. Are you a MoNkEy? If you haven't read Matthew S. Gast's 802.11 book published by OReilly and you
don't fully grok the implications of the shared MAC layer, you are just throwing nuts and filth from the treetops into the already busy ISM band.
Slashdot's coverage of other topics is relatively even. The coverage of radio is focused on 802.11[bag] and this is quite laughable most of the time
to those of us who have actually owned and operated a wireless ISP. Personally I think the editors ought to be giving us a whole lot more information
on ICOM's D-STAR, a 23cm (1.2 GHz) amateur band voice/data system.
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
Actually you can't use a 24db antenna with a 100mw card. The maximum EIRP allowed under the FCC for point to point is 8 watts (39db) and 4 watts for point to multipoint. If you use 100mw (20db) input into a 24db gain antenna, your total EIRP will be 44db or 25 watts. Not legal at all. Also not healthy to stand in front of the antenna for more than a few minutes.
Below is my rough, quick and dirty translation of the article. You will have to mach the text to the pictures yourselves. AND it's Polish, not polish. For the difference of meaning see your favourite dictionary.
----
Wi-Fi - World Record - 110 km @ 2.4 GHz
Two-way DSSS communication in 2.4 GHz band at a distance of 110 km
INTERLINE company, leading Polish microwave antenna producer, set itself a goal to check possibility of establishing a wireless link in 2.4 GHz band with sequential spectrum spread DSSS (802.11 b standard) at a range currently being only a subject theoretical dispute. The aim of the enterprise was a practical assessment of possibilities and study of phenomenas concerning such a link.
It should be stressed that the link built is typical ground link and that diversivies it from the one built at the end of 2002 by Swedish company Alvarion and Swedish Space Corporation, which used a stratospheric baloon.
What is equally important, all elements used in the INTERLINE experiment are off-the-shelf, unmodified equipment available comercially (1.1 meter parabolic antenna and a 500 mW amplifier). Swedish experimentators used 2.4 m parabolic antenna and a 6000 mW amplifier.
Two localisations were chosen for the link: Wrocaw (a city) and a Hala pod Sniezka (Sniezka is a highiest mountain of Karkonosze), S-W from Jelenia Gora. The distance is around 110 km.
People
In the experiment actively participated:
Piotr Kroplewski - owner of the INTERLINE
Wiesaw Karpowicz - Manufacturing Manager
Maciej Kaminski - Technical Division Manager
Krzysztof Mularczyk - Wireless Network Specialist
Krzysztof Juszczyszyn - Manufacturing Technologist
Localisations
One of a key stages of the experiment was a choice of localisations for stations which were to create a point-to-point link. First of them is a 11 stage house on a one of Wroclaw's districts.
Second one, key to the experiment, is a glade by the summit of nieka, nerby Dom lski shelter (1400 meters above sea level)
Equipment
For the experiment following equipment was chosen:
Antenas: PARABOLIC maxi, 27 dBi - product of INTERLINE
Access points: INTEL Pro/wireless 2011 Access Point - made by SYMBOL
Cables and connectors: cables BELDEN H-1000, H-155, RG-316, connectors VITELEC
Wireless cards - Lucent ORiNOCO PC Card Silver/chipset Agere, ZCom XI-300/chipset Intersil
aMPLIFIER - 2.4 GHz, 500 mW
Of course there were also 2 laptops. Additionally we had: UPS, a set of tools, spare cables, connectors and a gas solder (just in case).
End-point Wroclaw
As the date of the experiment was set a time between 12th and 14th of September 2003.
First stage was mounting and directing an antena in Wroclaw to point towards nieka mountain. Due to good visibility in Wroclaw in the day of installation (2003.09.12), this mountain, which is 1602 meters above sea level, was clearly ivsible. During the directioning vertical angle was important, due to the fact, that the other end of the link was 1400 meters above sea level.
Installation components
1. Access Point
INTEL Pro/Wireless 2011 Access Point + Amplifier 2.4GHz/500 mW
(here you can read yourself)
2 Antena cable
Belden H-1000
Length: 5 meters
plugs: type N
3 Connector
INTERLINE N/RP-BNC
Length 30 cm (0.3 m)
plugs: type N and RP-BNC
4 ANTENA
INTERLINE PARABOLIC maxi
type: directional parabolic antena
gain: 27 dBi
radiation angle: 4degrees/6degrees
Installation - Karkonosze mountains, Kopa-nieka
On 14th September 2003 all the equipment has been transported with OPEL Frontiera (we had obtained permission of the Karkonosze National Park authorities) to the meadow near the nieka's summit.
On the installation place weather was as usually in the mountains. Almost all the time the place was covered by clouds. Only from time to time for a dozen seconds wind split the clouds and we were offered splendid views of surrounding mou
You can run 1 watt into a 6dbi antenna. For point to point you need to reduce your transmitter power 1db for every 3db increase in antenna gain. This means the max antenna gain for 500mw would be 15dbi. Add 9db to the gain to get 24bdi and you need to drop power another 3db or 250mw. 100mw would be legal at 27dbi but not 500mw. Since you need to increase total gain 6dbi every time your double your distance this would make this shot easy with 27dbi antennas and 500mw amps. I have heard of 20 mile links using legal power levals/antennas. The 500mw amps make this easy. To do this legaly would require very high gain antennas perhaps more than 33dbi. This would be the max legal output for 125mw. Most really good radios put out 100mw. I imagine that a 8 foot dish feed with a biquad antenna might do it.
Any connection uses actually, the three channels around it for the connection anyways,
if you've ever tried actually haveing 11 acess points on different channels you'll notice massive interfearence
come comment on the madness at http://slashdot.org/~phreak03/journal/
All of the channels basically overlap with the other channels. However, if you're on 1, 6, and 11, you manage to cover the entire chart without duplicating yourself.
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.
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.
There is only 1-11 in the US.
-matthew
"THERE IS NO JUSTICE, THERE IS ONLY ME." -Death
I live right next to a university and I can see at least 15 different access points on any given day from my wireless link. I use it for internet access to the university and I can definatly tell when my neighbors are using their own LAN cause it causes a lot of packet drop outs. Not to mention about half of those APs have "linksys" as their SSID with no WEP enabled.
It gets better during the summer when a lot of the students around me leave and shut off their APs.
802.11 is the IEEE standard, and the 'b' section of that pertains to a wireless network capable of 11 MBps (the 11 in 802.11b has nothing to do with the 11Mbps theoretical throughput, just a coincidence.) In reality, 802.11a, b, and g operate in the 2.4 GHz range, like the 2.4GHz cordless phones.
I'm the Devil the Windows users warned you about.
The dogcow says "Moof!"
Based on reading the article they are talking about a software defined radio (SDR) which is capable of operating discrete carriers and user communities on each of the 3 non-overlapping channels. They are not talking about bonding all 3 channels into a single data link.
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....
Not really. The 802.11 definiton for the channels are not used by anything else. So, if your 2.4GHz's interface claims there's 20 channels, you just have to guess if those channels are just 1/20th slices of the same pie, or if they've jumped around in their numbering scheme so that one click can get out of the footprint of most problems. You really don't know what your own devices are doing, so how can you predict what the neighbor's are throwing in?
Trial and error it is...
The 2.4Ghz bandwidth used by 802.11b and 802.11g have overlaps. The 5Ghz used by 802.11a and upcoming 802.11h (802.11a with Power Management) have non overlapping channels.
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
You can read this for a little more info.
Unless of course, you want a faster speed. By my understanding Bluetooth is about 1/10 the speed of wifi (unless I heard wrong.) And that's just 802.11b, not g.
I've got more mod points and GMail invi
Incorrect. 802.11g's practical max throughput is around 25Mbps (Half of theoretical max) and even if all of your clients are running .11g cards, you have a shared bandwidth topology. Given the same restraints, the almost 100% bandwidth advantage of 100baseTX will show.
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)
"You've got an invalid haircut" -Warren Zevon - Life'll Kill Ya
That's a switched network, not a 'dedicated' one. Yes, the RF channel is a 'dumb hub' but many 100baseTX implementations are also 'dumb hubs'. 100baseTX Switches are ubitquous now, but that's only happened in the last couple of years, and many large networks are still hub based due to cost reasons.
"You've got an invalid haircut" -Warren Zevon - Life'll Kill Ya
For directionality to work, it requires widely spaced antennas (many meters), and this allows far more discrimination than your aerial.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Get the wifi detector from thinkgeek.com. It's just a 2.4GHz radio signal strength meter, and will tell you if anything is using that frequency. It's fun to use it in the kitchen while microwaving.
If you have the Linksys WRT54G, you can use a hacked firmware to get all 14 channels. Check out http://www.sveasoft.com/modules/phpBB2/viewforum.p hp?f=6 for the forums on how people are doing it. I'm not sure if you can hack the wireless lan card do access the same channels or not. They sell the WRT54G domestically and internationally. The chipsets can handle all the channels, but the firmware limits the US version to 1 - 11.
--
Retail Retreat
What Engim is doing is actually a good bit more sophisticated than any of the Slashdot posts imply. When you transmit, you usually have two types of bandwidth: how much bandwidth you are using, and how much you are interfering with. For instance, a simple AM broadcast will require maybe 8KHz of the spectrum on which it actually transmits data. Since transmitters are imperfect, however, it may actually interfer with transmitters on, say, 20KHz of spectrum.
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.
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. Japan's different than US/Canada.
The full ranges are in the kismet documentation if I remember correctly.
But the overlap is because the upper freqency for channel 1 is 2.423 while the lowest end for channel 6 is 2.426. 5 ranges from 2.421 to 2.443.
Still, the FCC doesn't have any say over what those channel mappings are; meaning that a cordless phone could easily interfere with those channels (and does).
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.
-rick