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Wireless LANs Face Huge Scaling Challenges
BobB writes with this excerpt from NetworkWorld:
"Early WLANs focused on growing the number of access points to cover a given area. But today, many wireless administrators are focusing more attention on scaling capacity to address a surge in end users and the multimedia content they consume (this is particularly being seen at universities). Supporting this involves everything from rethinking DNS infrastructure to developing a deeper understanding of what access points can handle. And 802.11n is no silver bullet, warn those building big wireless networks. 'These scaling issues are becoming more and more apparent where lots of folks show up and you need to make things happen,' says the former IT director for a big Ivy League campus."
...we're having the same issues we did when we stopped using dialup and moved to broadband?
Me failed English...
FreeBSD over Linux. If my comments seem odd, this may explain...
Bits of wire are dedicated to individuals, wifi spectrum is shared between individuals. Who'd have thought that might create scalability issues...
Perhaps dedicating a little bit of the spectrum to each individual might fix the scalability problems.
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We're having the same scalability issues which existed with 10base2 technology and 10/100baseT on a hub. The solution is "the switch".
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"Perhaps dedicating a little bit of the spectrum to each individual might fix the scalability problems."
Perhaps an understanding of physics would help even more.
Who would have thought you actually had to plan a network rather than just throw some hardware in place?
PPP==PPP* all over again.
*Piss Poor Planning == Piss Poor Performance
Cellular communication systems get around scaling issues by having smaller cells. A single base station might actually support four cells in different directions. I wonder if you could build a wifi antenna with a single lobe, then cluster the antennas to give a multi lobe access point.
The base station would have to support multiple antennas but this wouldn't need to require a lot more transceiver hardware. The antennas could be multiplexed.
http://michaelsmith.id.au
There was a very interesting research article about DenseAP, which tries to solve this problem, in the latest issue of ;login:. Unfortunately it's still subscribers only. But for Usenix members it's on the link below, and other might find something on google :)
http://www.usenix.org/publications/login/2008-08/index.html
Erik Dalén
Who uses Wifi but other than....oh wait....
But today, many wireless administrators are focusing more attention on scaling capacity to address a surge in end users and the multimedia content they consume
Here it is after the fixing.
You don't grow any infrastructure by constantly adding new 'beta' or badly interoperating devices on top of it, that is all wrong and in case of 802.11 it makes a noisy mess out of a tiny radio spectrum: giving the exact opposite result.
The magic world I think is 'convergence' of technologies. Try to cooperate with each other and build a fully standard infrastructure that does good to all.
The example is invention and spread of electrical power. Think utility, not commodity.
It is hard in a toughly individualized and disgregating society, but can be seen like this: we are sitting on a huge copper mine in 1896.
Not exploiting it, with a bit of patience and respect, would be against our own interest, in a word: dumb.
The fact is that this is "Radio" for all its worth. The "radio" part is what carries the signal much like the Cat5e does with the wired stuff. The problem is that people are thinking and going about this from the wrong direction. I saw some of this years back when all we had was 802.11b and we tried to fill up a wireless access point with as many connections as we could. The access point started dropping connections erratically, and bandwidth to all connected users were suffering after only about 10 or so users doing concurrent and sustained file transfers. We tried this again later with 802.11g and pretty much got the same issue.
All they did with 802.11g to get faster throughput, was to spread the signal out wider so it covers up about 3 channels to what 802.11b uses. It didn't really change the fundamental way in which the radio "wire" is connected and how its accessed. The sender/receiver can only handle just so much through it.
This is not really a scaling issue and being able to resolve a large number of hosts behind an access point, but really more of change of the fundamental design of the "carrier" in the first place. My assessment here is that our so-called "Wifi" will actually have to morph to a cellular type of radio rather than what we have now in order to properly scale. A cellular method will carry with it a multi-channeled multi-homing sender-receiver that can better handle multiple connections unlike a single transmitter/receiver pair used to handle the whole lot.
Just my humble opinion.
All content in this message is copyright (c) 2008. All rights reserved. RIAA is prohibited here.
At the end of the day the electromagnetic spectrum can carry only so much information using a given number of frequencies. If you want to send data at this and that many bits per second, you are going to need a frequency with a similar number of periods per second. Ok, it's not quite that simple, but at the end of teh day higehr data rates means you need higher frequencies. If you fix the frequency that instantly caps the theoretical maximum amount of data you can transmit. There are two ways to adress this:
a)Increase the frequency
b)Deploy more access points so you are less likely to have many computers using the same one.
The second alternative is essentially equivalent to using more wired networks and fewer wireless ones. Even if all teh comunication in the network is done in some sort of p2p mesh, increasing the number of access points increases hardware costs, which is teh same problem as you have with wired networks.
Thus to get large data throghput you need to increase the frequency. Eventually you reach frequencies where the lightwaves no longer bend around obstacles and you will need a waveguide, such as telephone line, a coaxial cable , or optic fibre. This is why wired networks will always outperform wireless. By using a waveguide you are not limited in frequency by the requirement that the signal should have a wavelength long enough to dodge obstacles and difract around corners, and thus you can increease the frequency far beyond what you will ever achieve with wireless comunication, hence getting better bandwidth.
These are physical limits, not merely technological ones. If you want high bandwidth you will need high frequencies, which in turn means you will eventually need either line of sight between the nodes or a waveguide ( wire ). Ok, theoretically something like a proton beam has a frequency so high you will be limited by other things ( such as energy consumption ) rather than frequency, but you need line of sight for those as well. I guess if you used neutrinos or some other very penetrating radiation you would always have line of sight, but barring any sudden breakthroughs in neutrino detection/generation I doubt that is going to be practical for simple data transfer any time soon.
Project died. I guess. Poles are still all over half the suburb.
Yeah right. I don't pay for texts. They're .20 if I use them.... If a text was 5k, which I know it's less... that's 1024/5*.20.... over $100 per MB...
If they want us to use text, they're going to have to makei it free.
Do not meddle in the affairs of sysadmins, for they are subtle, and quick to anger.
2.4 Ghz is full. 5 Ghz is not so good for many users. It would have been great is some of that recently freed up TV spectrum was made available for wifi.
My guess is that within a couple of years there will be 'grey-market' wifi devices that operate in other bands, illegal to use in the US and many other countries but used nonetheless, much as extended-range cordless phones and the CBs of old.
Regulators would be wise to head off the problem by freeing up some spectrum for additional wifi bands right now.
Another method would be to use the interstices of channels in existing, older services for a collection of narrow band digital channels. The 800mhz AMPS and 900 mhz GSM cellular bands might be good candidates for this. The problem is that cell phones using these bands may cause interference in when in close proximity to devices using these new wifi bands.
if you've got too many people hogging an access point, maybe you should think about implementing some kind of bandwidth throttling or traffic shaping. man tc.
WiFi falls back to lower data rates when signal conditions force them to. Beacons are sent at the lowest data rate, 1 mbps. If access points refused to lower their data rate beyond some threshold, then more bandwidth becomes available on a given channel. The noise floor will also drop. Of course, some users will not be able to use the network because they can't connect at a higher data rate, even with the drop in noise floor. But many of these will be outliers, or people who aren't actually on campus but using campus networks. Too bad for them, assist legitimate users in upgrading equipment.
If you didn't have the restrictions of backwards compatibility, you could drop support for 802.11b and DSSS completely, and have an 802.11g network. DSSS is less efficient than OFDM when in close proximity. Again, distant users are at a disadvantage.
If you've ever sniffed a large wifi network you'll see alot of junk traffic, mostly from cisco and microsoft protocols which were meant for a wired environment where bandwidth is cheap. Filtering these at the AP can help the bandwidth problem.
OK, there's my consulting for today. My bill is in the mail.
Who else read between the lines that you could boost your AP signal by grafting your microwave and linksys? Sure, if you want to use you laptop from the other end of the neighborhood, you'll have to upgrade the laptop's transmitter too. But I'm all about having the biggest WiFi on the block. It'll match my SUV, boat, house, wife (trophy hot big, not grossly large big), and everything else that treats my little dick syndrome. And fuck my neighbors too, it's my spectrum space cause my taxes pay for it.
A few points that might help scalability and transfer rates:
* Larger spectrum with the ability to use slightly higher power output for increased range. Universities and corporations that require higher output would be designated a section of that spectrum as to not interfere with nearby residential wireless equipment. It is obvious that the current 2.4GHz wireless spectrum is oversaturated with devices. Given that most users leave the wireless channel on the router's default setting (not to mention the security set to none), it is no wonder that many experience connectivity issues, but that's besides the point. Onto the next item...
* Adaptive/Cooperative router software and end-user drivers, which would be especially helpful for load balancing purposes on university campuses and other applications.
Example: Routers setup in WDS mode would update each other (on a wireless sub-channel) on current amount of users, distance from each other using simple calculations, etc. Using that data, the wireless client would be directed to which nearby router to connect to and stay there for the duration if at all possible. Some would say that it would be akin to the way cellphones work. That information would be updated periodically on the client end in the event they move around campus and away from their current AP. Unlike current WDS which requires the wireless channel to be fixed, this next-gen WDS, if you will, would allow for separate channels to mitigate interference between APs. Client software would be provided a list of nearby authorized APs. Preventing rogue APs and other security-related issues is another discussion altogether, but very important for any kind of wireless communications.
* QoS that actually works, especially critical with larger scale deployments. This would obviously require work on both ends, router and wireless client. Give the router the ability to deny connectivity if the client does not have QoS enabled on their end. Or better yet, allow the client to connect and redirect any http request to a page stating that given the fact that QoS is not enabled, they will not be able to continue and subsequently disconnect them. Implement a ban period for repeated connectivity requests without QoS enabled and notify the rest of the APs within their network to simply drop requests from the given MAC address until the ban period expires. Of course, those in the know would change their MAC via software and try again, but as I mentioned earlier, this discussion is security measures aside.
* All of this extra work would not without a price. New multi-core CPUs would need to be employed with efficient embedded software that would load-balance properly and have redundant memory and other equipment for high-availability. Of course, this is in reference to larger deployments like a university and the like. As the desire for constant wireless connectivity continues, maintainers must ensure that their installed equipment can handle minor hardware issues like power supply failures. It would also make their lives easier as they would simply tap into a stash of spare parts, replace the part in question and the end user would be none the wiser. It would be akin to replacing parts on a server. It would ensure that the help center does not receive a flood of calls because their pr0n/torrent stream stopped working. LOL!
- Just my $0.02 -
Comments/rants welcome...
I saw the headline and thought "What? Wireless LANs and face-huggers? Huh?"
Definitely need more coffee...
Don't underestimate the power of The Source
You're exactly right, very few people understand wireless. Heck, many people in IT probably don't understand the difference between a switch and a hub. An 802.11n wireless AP is essentially a 100 Mbps hub under IDEAL conditions since the hub doesn't really have to deal with signal strength, interference from other hubs.
I couldn't believe the article suggested that it would be a good idea to use 160 Mbps 2.4 GHz 802.11n. That would effectively cut your capacity down to half because you'd be using 40 MHz channels. We only have 60 MHz in the 2.4 GHz band total (80 MHz if we include the guard bands between the channels).
It's also weird that they would complain about 5 GHz not penetrating walls as easily. The whole beauty of 5 GHz is that you can't penetrate walls as easily so you can put an AP in every room and not have to worry about as much interference between the APs. The scalability issues go away if you do one AP per room. Heck, they use 24 802.11a access points on every possible channel on the trading floor of the NY stock exchange to maximize performance.
Cellular systems use even LARGER cell sizes than Wi-Fi. Hell, it's not even in the same ball park. Cellular providers generally have even less spectrum than Wi-Fi and even the biggest companies only have around 100 MHz. The 2.4 GHz band alone has 80 MHz and the 5 GHz band has 480 MHz of total unlicensed spectrum. The difference here is that the cell providers have exclusive access to that spectrum and they're extremely careful about how they ration the resources.
"Unfortunately the math there is harry, and one of the upcoming technologies making use of beamforming, namely WiFi has failed to deliver thus far." Well I think I see your problem right there. Harry is have "performance under pressure" issues.
Shai Schticks:"You don't make peace with friends, you make peace with enemies"
Video artifacts and loss of audio is the result.
To put it simply, guess Networkworld has missed the arrays Xirrus makes. Plus, it helps to be upgrading the back end wired equipment (switches, routers, even cabling) to support the faster requirements. Just my penny thought.
Agrisea Tsunami - Epyc Servers... https://agrisea.net/products
APs arent five for a dime ya know...
I know tobacco is bad for you, so I smoke weed with crack.
You either spend the money on the Access Points and limit the number of users to a few people per AP or you deal with over crowding on a few APs. If you want the performance, you need to pay for good infrastructure. You can't expect good performance when 100 people are sharing 24 Mbps of bandwidth on an unmanaged wireless hub with a single collision domain.