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Wireless LANs Face Huge Scaling Challenges

Soulskill posted more than 5 years ago | from the blame-youtube dept.

Wireless Networking 89

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."

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PENIS (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#24808275)

Goes where?

So basically (4, Insightful)

Architect_sasyr (938685) | more than 5 years ago | (#24808299)

...we're having the same issues we did when we stopped using dialup and moved to broadband?

No (4, Insightful)

Colin Smith (2679) | more than 5 years ago | (#24808335)

We're having the same scalability issues which existed with 10base2 technology and 10/100baseT on a hub. The solution is "the switch".


Re:No (4, Interesting)

Stellian (673475) | more than 5 years ago | (#24808615)

The solution is "the switch".

In the case of wireless, the role of the switch could be fulfilled by beamforming [wikipedia.org] : a breakthrough that allows the same spectrum to be used by multiple transmitters simultaneously, as long as they are physically separated.
Unfortunately the math there is harry, and one of the upcoming technologies making use of beamforming, namely WiFi has failed to deliver thus far.

Re:No (1)

Stellian (673475) | more than 5 years ago | (#24810935)

WiFi has failed to deliver thus far.

I meant WiMAX, of course. Beamforming is also included in the 802.11n, I don't know how well it implemented by the early adopters.

No-Strain Gauge (1)

Ostracus (1354233) | more than 5 years ago | (#24812971)

"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.

Re:No-Strain Gauge (1)

KGIII (973947) | more than 5 years ago | (#24818407)

He's unhappy because the sequel wasn't written, it was meant to be, "Hermine (spelling???) Lets Harry Touch Her Breasts."

Re:No, no, the approach is wrong (0)

Anonymous Coward | more than 5 years ago | (#24808833)

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.

Re:No (1)

jstott (212041) | more than 5 years ago | (#24813133)

The solution is "the switch".

In 802.11b/g operate on the 2.4000-2.4835 GHz band (so saith wikipedia [wikipedia.org] ). That gives you 83.5 MHz of total bandwidth, for a theoretical maximum allowed data rate of 41.75 MBit/sec, or roughly 4 MByte/sec. It doesn't take too many torrents or video streams to suck up 4 MByte/sec (and that's the theoretical maximum, actual performance usually caps at at about half the theoretical max!).

The problem isn't switching, it's having enough non-interfering access points to deliver the bandwidth needed (desired) by the end-users. Unlike copper, with wireless you get to a point where you can't add any more access points in a given area because all the (non-overlapping) channels are already being used — there's simply no more bandwidth left to allocate.


Re:No (1)

Hunter-Killer (144296) | more than 5 years ago | (#24813911)

In 802.11b/g operate on the 2.4000-2.4835 GHz band (so saith wikipedia). That gives you 83.5 MHz of total bandwidth, for a theoretical maximum allowed data rate of 41.75 MBit/sec, or roughly 4 MByte/sec. It doesn't take too many torrents or video streams to suck up 4 MByte/sec (and that's the theoretical maximum, actual performance usually caps at at about half the theoretical max!).

I don't have the technical expertise to adequately explain modulation [wikipedia.org] , but your understanding of throughput calculation is severely lacking. Standard 802.11g is able to offer 54Mbps (theoretical) in only 20 MHz of bandwidth.

Re:So basically (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#24808525)

...we're having the same issues we did when we stopped using dialup and moved to broadband?

test by vijay

Re:So basically (4, Interesting)

azgard (461476) | more than 5 years ago | (#24808679)

No, I think we are having these issues, because we are going backwards. It's like going from cable TV back to the wireless broadcast. If we were doing that, we would have less TV channels to select from.

Re:So basically (2, Informative)

Bazman (4849) | more than 5 years ago | (#24809217)

Not really, it all depends on the cable! I just had my house re-roofed, and up there in the eaves were a bunch of old cables and a plastic box marked 'Rediffusion':

http://rediffusion.info/cablestory.html [rediffusion.info]

I think that system delivered about 5 tv channels, probably in black and white too. Nowadays I get 40 TV and radio channels over a terrestrial wireless broadcast system.

Re:So basically (1)

azgard (461476) | more than 5 years ago | (#24810617)

Actually, I used "we", but I am not American (I cheated a little :-)). In my country (Czech Republic), there are about 4 available channel frequencies for terrestrial wireless analog TV broadcast in Czech (this has probably to do with the fact that in Europe, different states require different sets of channels). However, with the cable, you can get some more, as well as other European channels (I would say 30-100 channels). This will probably change with the switch to digital broadcast - then it will be possible to fit several channels into one analog frequency.

However, my original point still stands - in wireless, there is limit to number of channels / amount of data you can move through the air. With cable, while there is a physical limit, it is a lot higher.

Re:So basically (1)

Belial6 (794905) | more than 5 years ago | (#24810881)

And that physical limit can be overcome by pulling more wires. Yes, more bandwidth can be allocated for wireless, but RF is already pretty crowded.

Re:So basically (1)

orasio (188021) | more than 5 years ago | (#24819621)

Yes, that happens to me. DirecTV made me go back to only receiving 500 channels at the box.
That is a drawback, from the 10000 channels I had when I used coaxial.

TV is esp. the best scenario for wireless distribution. You have very few transmitters, and loads of receivers, no conflict resolution. It's so good, that they only keep using cable because of its limited access, better for control and billing.

And I don't understand what you mean by "going backwards". I really like typing this from the bed, in a rented apartment. When I'm at work, I have an ethernet cable, but I never bother to plug it. It's just easier, and good enough for most use case scenarios. Not all of us are into video editing.

Some times, convenience is more desirable than throughput.
Decreasing some metric in some cases, like bandwidth, doesn't mean going backwards, if it involves other changes.
Trains can travel faster than cars, but lots of people like the convenience of choosing their destination. I don't think it's going backwards. There is no single line forward.

Re:So basically (1, Funny)

Anonymous Coward | more than 5 years ago | (#24809083)

...we're having the same issues we did when we stopped using dialup and moved to broadband?

We're having the same problem we had before we moved away from sparkgap transmitters.

Hmmm (4, Insightful)

Colin Smith (2679) | more than 5 years ago | (#24808323)

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.

Re:Hmmm (4, Insightful)

thompson.ash (1346829) | more than 5 years ago | (#24808369)

Surely dedicating a segment of that spectrum would cause problems ensuring equality of access?

At the moment it seems that the more people you have on, the lower your bandwidth - stands to reason.

Surely allocating fixed bandwidth on a first come first served basis would mean eventually you would run out of bandwidth to allocate and people would be denied access?

Re:Hmmm (4, Interesting)

nuintari (47926) | more than 5 years ago | (#24809951)

802.11 clients can send and receive pretty much whenever they want to, the access point is expected to work it out, and clients are all expected to behave themselves. 802.11 also makes the assumption that all the clients can see each other, they frequently cannot, which is called the blind neighbor problem. Individual clients will badger the access point like mad, and if they cannot see each other, which is basically how they are supposed to know when to stop transmitting briefly, the AP becomes a single waiter in a huge restaurant, and everyone is ordering at the same time. Stuff gets dropped. The more clients you add, the worse it gets. As the load on an access point increases as a linear function, the performance for each individual station drops exponentially.

The solution is to give the access point all the control over who sends, who receives, and when. Take it one step further, sync all the access point clocks to the same timing system, most non 802.11 alternatives use the GPS timing pulse for this, and now you can reuse frequencies on access points in relatively close proximity.

One of these days, someone is going to realize that 802.11, common as it may be, and as universal as it may be, is not the way to go.

Re:Hmmm (1)

evilviper (135110) | more than 5 years ago | (#24813041)

The solution is to give the access point all the control over who sends, who receives, and when.

Ah yes, "token ring" WiFi... I like it.

Re:Hmmm (1)

nuintari (47926) | more than 5 years ago | (#24815301)

Your analogy is rather lacking, and I encourage you to explore several real world non-802.11 wifi implementations that deploy this concept, all with much more success than your average 802.11 shithole.

Suggested reading: dragonwave, canopy, trango

Re:Hmmm (1)

WhiteHorse-The Origi (1147665) | more than 5 years ago | (#24827065)

How does a linear function of load cause an exponential drop of performance?

Re:Hmmm (1)

cbiltcliffe (186293) | more than 5 years ago | (#24829615)

If you have an AP with one client connected, there are no conflicts.
If you have an AP with two clients, you have conflicts between clients A+B.
With three clients, you have conflicts between A+B, A+C, and B+C.
With four clients, conflicts between A+B, A+C, A+D, B+C, B+D, and C+D.

See how it's jacking up pretty quickly?

Re:Hmmm (1)

WhiteHorse-The Origi (1147665) | more than 5 years ago | (#24830221)

So A has conflicts with n clients, B has conflicts with n clients, then you have nx(n-1) conflicts, or n^2-n conflicts. However, not all clients can conflict at the same same time, so there must be (n-m)x(n-1) conflicts. Both of these are non-linear, but not exponential.

Re:Hmmm (1)

Colin Smith (2679) | more than 5 years ago | (#24811991)

Surely allocating fixed bandwidth on a first come first served basis would mean eventually you would run out of bandwidth to allocate and people would be denied access?

You mean like running out of ... ports ... in a hub or a switch?


Hmmm-Shannon (0)

Anonymous Coward | more than 5 years ago | (#24808387)

"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.

Re:Hmmm (4, Interesting)

Tony Hoyle (11698) | more than 5 years ago | (#24808465)

Technically bits of wire (beyond the first hub anyway) are shared as well.. they just have a much higher bandwidth so you don't notice.

This article could have been written 5 years ago.. don't see what's new - everyone knows wifi doesn't really scale, which is why you keep it to small defined areas like a room per AP (and keep your important infrastructure wired as far as possible). If that's news to an admin then they probably skipped a few classes...

Re:Hmmm (5, Interesting)

mikael_j (106439) | more than 5 years ago | (#24808547)

I suspect you'd be amazed by the number of supposedly technically proficent individuals who don't understand that with WiFi you have to essentially share bandwidth with every other computer and AP using WiFi nearby.

I used to do first and second line tech support for a line of wireless APs, more than half the calls were from people (who in a lot of cases should've known better) who were pissed at their AP for not letting them connect while there were at least ten other APs nearby...

Unfortunately a lot of people see WiFi as either a necessity or some kind of "solution" to their cable "problem", and lord have mercy on any fool who suggests that they connect their home NAS using a regular wired network and simply hide the cables, no no no, they NEEEEEEEEEEED WiFi for their home NAS.


Re:Hmmm (2, Funny)

thompson.ash (1346829) | more than 5 years ago | (#24808645)

I'm the first to admit my knowledge on this is limited...

I read /. in the vain attempt to learn stuff that my piss-poor university neglected to teach me!

Congrats guys, you're all honourary lecturers!

Now keep talking, I'm trying to take notes here!

Re:Hmmm (5, Insightful)

walt-sjc (145127) | more than 5 years ago | (#24808731)

You will find a large number of those individuals right here on /.

About a year or so ago there was a discussion about WiFi, and I mentioned that I wired my entire house with the standard 2 RG6U, 2 Cat5e, 2 fiber to every room, sometimes two drops in a room. I have jacks EVERYWHERE. People said I was nuts. I said I was future-proofing - they claimed wireless would get faster too. And the response is Of course it will get faster, but so will physical cable as we have seen.

The bottom line is that wireless can not and will not replace physical cable. It can only supplement. Primary connectivity should always be planned to be wired. Yes it's more expensive. A LOT more expensive. But you need it.

Wireless by nature is flaky. I can have a laptop 10 feet from an AP and it can drop connection (and I don't care what brand of laptop or AP you have - it happens.) Why? Because the primary wireless frequency, 2.4Ghz, is a cesspool. I find it highly obnoxious that the FCC refused to allocate a band specifically and ONLY for WiFi - especially considering how extremely important connectivity is in this modern world. But Alas, they are only concerned about how much money they can bring in via auctioning off a PUBLIC resource, selling it to a corporate entity which in return lets the public use that band for insane prices.

Re:Hmmm (2, Insightful)

Anonymous Coward | more than 5 years ago | (#24808955)

You have heard about that other part of WiFi - "A"
which is where the N feature is used effectively and due to the multiple portions of spectrum used by "A" you should really have less issues.
Toss in MIMO and you have a winner.


Re:Hmmm (2)

rukcus (1261492) | more than 5 years ago | (#24812217)

Mod parent up.

802.11b/g really is overcrowded. It doesn't help that you have to pay a premium on laptops that offer 802.11a/b/g(/n). Additionally, APs cannot offer full 11MB/s for B and 54MB/s for G in all zones. This is, afterall, a radio device, and follows radius-squared laws for intensity of signal. The farther you move away from the AP, the less signal you will receive and slower throughput.

Re:Hmmm (1)

walt-sjc (145127) | more than 5 years ago | (#24828779)

Of course - while the 5Ghz band is much less crowded, it has other issues - the higher you go in frequency, the less ability you have to go through walls. You trade one problem for another.

Re:Hmmm (4, Funny)

Anonymous Coward | more than 5 years ago | (#24809277)

Yes. Get the hell out of my 2.4 range.
      ~ HAM Radio guy

  (those astrofolks enjoyed it as well).

Re:Hmmm (4, Insightful)

Migraineman (632203) | more than 5 years ago | (#24810067)

802.11whatever is an access point solution. Folks who expect it to be a backhaul or backbone solution are ... not well versed in network architectures. I find it amusing that folks think an ad-hoc mesh of 802.11 nodes will *ever* have performance comparable to wired/fibered connections. Just the "shared medium" aspect should be enough to indicate performance will degrade as more connections are added. Shoveling more nodes into the mesh won't magically improve performance.

Eh, it doesn't surprise me. Evidence of this logical disassociation is everywhere - digital cameras, cars, appliances, computers, tools ... Listen carefully and you'll hear the cries of the oppressed - "I don't want to know how it works, I just want to [do blah]."

Re:Hmmm (4, Interesting)

adolf (21054) | more than 5 years ago | (#24810219)

And don't forget microwave ovens. It's likely that everyone reading this has a 2.4GHz radio, of power levels ranging from several hundred Watts to over a kiloWatt, in the form of a small microwave oven in a nearby kitchen. Yeah, sure, it's shielded and lead screened and whatnot. But it doesn't take much leakage to completely trash the signal from a common Linksys WRT54G, which only has a 28milliWatt transmitter.

Further, at these high frequencies, RF can act a little strange -- my own microwave didn't cause any noticeable interference, until I moved to a different house. After the move, with the same microwave, the same access point, the same laptop, and similar SNR, everything ground to a halt whenever the microwave was in use. Both houses have modern wiring and good grounding. The only real difference is that the microwave is now rotated 180 degrees relative to the portions of the house where there is WiFi gear, which seems to indicate that the oven leaks more in some directions than in others. Switching channels seems to have worked around this issue.

For reasons like this, as part of the ongoing remodel and rewire, every room gets at least two Cat5e, at least one RG6, and a polyester pull string to some accessible area. (I'd have run some multimode fiber, but currently don't have anything which needs it, don't have any problems which can be solved with it, and don't have any experience terminating it. The pull string should make it easy to install later if the need ever arises.) The wiring, including coax, terminates at a couple of ICC keystone patch panels in an otherwise-useless alcove next to the basement steps, which is also where the switch, routers, and cable modem live.

Some rooms have more drops than others, like the game room and the library. The office has about a dozen RJ45 jacks, mounted both along the baseboard at regular outlet height and midway on the wall (just above the height of a monitor on a desk) for plugging all manner of things in temporarily for servicing or toying or whatever.

People think I'm nuts, too, but I'll have more bandwidth available to more independent points than any wireless technology will be able to provide for the foreseeable future. I can plug in new gaming systems, or analog/IP telephones, whatever audio or video gear, or about anything else, wherever I want, without worrying about coverage issues, while keeping my WiFi spectrum clean for those tasks that need it, like listening to Pandora way out in the back yard next to the fire ring with an iPod Touch.

Structured cabling isn't a problem which needs solved, but a solution for all manner of things which need connected.

Re:Hmmm (2, Informative)

Belial6 (794905) | more than 5 years ago | (#24811301)

I don't recommend running cable to every place that you MIGHT need it. When I do remodeling, I run 'smurf tubing' down the wall in every room. It isn't really any more expensive than running 'just in case' wire. The benefit is that you don't have to worry about what kind of cable you might need in the future. I did this on my last house. When I remodeled each room, I put in a 2" tube from the attic to a face plate in the wall. I didn't pull a single wire until the place was done. After the house was done, I just fed the coax, phone and cat 5e cable to each of the places I needed it.

Re:Hmmm (1)

adolf (21054) | more than 5 years ago | (#24813759)

That's nice, and all. But:

Needs arise at odd times. I don't want want to worry about climbing around in the attic with a 2-man pulling crew just because I've picked up a uPnP media player for the bedroom, or whatever -- I want it to plug in and work. I'd also like my patch panels to be nice, neat, and obvious in their layout; these goals range from difficult to impossible when cabling only happens on an as-needed basis. Further, given a choice, I'd really prefer to only visit each location one time, instead of at least two times. And, given a choice, I'd always rather spend less money than spend more money. And if/when new needs arise they are easily solved with the installed pull string.

It helps my situation in that the wiring was free -- I've been collecting short boxes of Berk-Tek Cat5e from work that were on their way to the dumpster.

For me, I don't really see the purpose of smurf tube or any other conduit when it comes to low-voltage cabling. It doesn't make the wire work any better, and it doesn't save any time. I'd still have avoided the smurf tube method even if I'd had to pay for all that copper. The pull string, on the other hand, is positively a no-brainer -- it's cheap, and comes in a bucket that is bloody easy to feed out of. Just tape the string into the bundle of wires, and pull the whole bundle (2 or 3 Cat5, one coax, one string) from the basement to the wall plate.

Really, the only time I can see using smurf tube smurf tube is in the event that the walls are insulated with batting. At my place, the walls are empty for now, which makes cabling a breeze. Later on, they'll be stuffed with blow-in, but the pull string will still work just fine afterward.

To each his own, I guess.

That sounds like a project... (0)

Anonymous Coward | more than 5 years ago | (#24811765)

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.

Re:Hmmm (0)

Anonymous Coward | more than 5 years ago | (#24808735)

That's not quite the described problem. A university campus network team typically has control over the arrangement of access points (except perhaps in dorm areas). Bad channel and SSID choices are not causing the congestion. One thing which cellphone networks do better than wireless LANs is the handover: Most access points allow clients to slow down when the signal is too bad for high speeds. Slowing down means that the client uses up bigger time slots for the same amount of data. The same happens with old 802.11b clients on 802.11g access points. Combined with the shared medium and the lack of a proper handover mechanism, the slow clients jam the network. Another problem with wireless LANs is the access protocol: Similarly to unswitched ethernet, the clients send when they want and back off when there is a collision. This works well with low to medium loads, but causes lots of overhead with high loads. This problem is amplified when clients are on opposite sides of the access point and can't see their client-client collisions because they are too far apart from eachother.

Re:Hmmm (0)

Anonymous Coward | more than 5 years ago | (#24809905)

The thing is many do neeeeed wifi for their home, myself included. I have a fully wired network in my home, cables going under carpet to every room with a hub in every room. It works perfectly for all of my actual computers, but the moment you get a laptop it becomes a problem. There's only so many places you can hide cables, and often I'm doing work that requires a constant network connection but with me migrating between rooms. When you're running tests on your laptop lasting several hours it is incredibly inconvenient to be forced to stay put. One other fact is that I live on the third floor with a shared garden. I often go sit in the garden as it's nice, however running a network cable from my bedroom window to the garden is just silly and incredibly inconvenient, although it does work.. My wireless reaches down to the garden so I can carry on with my work outside. Wireless is rapidly becoming a NEEEED, just to provide the required flexibility of living normally.

Re:Hmmm (1)

mikael_j (106439) | more than 5 years ago | (#24811131)

Excuse me? Being able to access the net from your garden is something you need in order to live a normal life? Maybe I'm a bit old-fashioned (After all, I am 26 years old) but since when is "broadband connection in garden" something that is needed to live a normal life?

Admittedly I do have a wireless AP myself but it's only there for convenience and I don't rely on it (unlike all those people I mentioned who, in most cases, don't even have any network cables available to plug their computers in with should the wireless fail due to circumstances beyond their or my control).

There's a difference between admitting that a notoriously fickle and troublesome technology being useful and convenient when it works and relying on it for anything that is "mission critical" regardless of if it's for your personal life or for work.


Re:Hmmm (0)

Anonymous Coward | more than 5 years ago | (#24811775)

Ok, so wireless in the garden is not a need as such, that was just a convenience point. What I meant is that it causes an awful lot more hassle and inconvenience to have to deal with cables on a laptop, and with that hassle, people start turning it into a need because it can make their lives so much easier. If however, they're people using a pc not a laptop, and they insist on using wireless then yes, they're muppets for speed and reliability reasons, but somebody with a laptop in their flat it is very easy to understand the need. It shouldn't be completely relied upon and a cabled network will always be faster, stable and more private, but in many circumstances this is actually an inconvenience and a last resort.

I think I may have read your post too fast earlier and missed the point of it (sorry), but wireless is a need for many many people.

Re:Hmmm (2)

rukcus (1261492) | more than 5 years ago | (#24812181)

And then you realize that routing wires in false-ceiling environments actually IS more expensive than setting up AP from ceiling mounts. You essentially reduce the total amount of cables by a factor of 10.

Ever heard of Cisco's Unified Wireless Architecture?
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps430/prod_brochure09186a0080184925_ns337_Networking_Solution_Solution_Overview.html [cisco.com]

Let's remind ourselves here for a moment: large networks are not easy to set up. You run into a number of problems including backend, connectivity, and end user access. The CUWN makes it easier by allowing you to control the AP (Lightweight AP's really - they only work in conjunction with a controller) from a central hook, and you can set the entire scope's settings. It also has guest access features which the article mentions.

Sometimes Wired networks aren't the most straightforward to get a building network access.

An additional feature is being able to seamlessly migrate from AP to AP based on radio signal to noise ratios. This allows the network to authenticate the most appropriate AP to the clients based on load.

You're exactly right, very few people understand (3, Informative)

George_Ou (849225) | more than 5 years ago | (#24812709)

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.

Re:You're exactly right, very few people understan (1)

badkarmadayaccount (1346167) | more than 5 years ago | (#24817395)

APs arent five for a dime ya know...

There is no free lunch (1)

George_Ou (849225) | more than 5 years ago | (#24824263)

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.

Re:There is no free lunch (1)

badkarmadayaccount (1346167) | more than 5 years ago | (#24856193)

OR, you could allocate more spectrum, and have each AP client on a separet chanell. 'course, the goverment and big ISPs would never allow it.

Re:There is no free lunch (1)

George_Ou (849225) | more than 5 years ago | (#24859851)

Huh, what are you talking about? I said you need to build a lot more Access Points in to your infrastructure. I did not say you need a separate channel for each access point.

Designing a proper wireless network means you need to put nearby APs on a separate channel with sufficient isolation. You do not need a separate channel for each AP. There's 80 MHz of spectrum in the 2.4 GHz range and 480 MHz of spectrum in the 5 GHz range. Even the largest cell phone providers only have around 100 MHz of spectrum they purchased from the FCC and they make do with it.

P.S. You could run your stuff through a free spell checker in Mozilla Firefox or something.

Re:Hmmm (1)

nuintari (47926) | more than 5 years ago | (#24809859)

And the switch they all plug into is a shared resource. Its a network, everything comes down to a shared resource eventually. The questions are, how much is there to share, and how well is it being shared?

Spectrum can be doled out in a very fair and efficient manner for everyone, unfortunately 802.11 doesn't even try to accomplish this. 802.11 is a colossal failure from a design standpoint. The clients can overwhelm an AP not because spectrum is finite, it is, but that isn't the problem, but rather because the protocol is so bloody awful.

Look at some of the alternatives available, Canopy, Trango, Dragonwave.... Those are the three I have the most experience with, there are many more. They all deliver what they promise, and they all scale very, very well. You ever seen even a lightly loaded 802.11 access point actually deliver anywhere close to what the box claims it will do?

If you had to choose (-1, Troll)

Anonymous Coward | more than 5 years ago | (#24808413)

If you had to choose between being a nigger and being a faggot, which would it be?

Re:If you had to choose (-1, Flamebait)

Anonymous Coward | more than 5 years ago | (#24808425)

i'd choose your nigger cock loving mother, obviously

Re:If you had to choose (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#24808601)

How about both, I've always wanted to join the GNAA.

Well duh (0, Offtopic)

banbeans (122547) | more than 5 years ago | (#24808447)

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

Re:Well duh (0)

Anonymous Coward | more than 5 years ago | (#24808897)

When did people start eBaying 6-digit UIDs?

Re:Well duh (1)

MadnessASAP (1052274) | more than 5 years ago | (#24813691)

(PPP==PPP) = Does Piss Poor Planning result in Piss Poor Performance?

(PPP=PPP) = Piss Poor Planning results in Piss Poor Performace.

Minus 5 geekpoints for you!

Directional access points (2, Interesting)

MichaelSmith (789609) | more than 5 years ago | (#24808577)

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.

Re:Directional access points (3, Insightful)

atomico (162710) | more than 5 years ago | (#24808959)

Access network planning and optimization is a big expense for mobile network operators: selecting sites, anntenas and channel allocation, base stations, base station controllers... lots of complexity which has to be handled carefully to obtain a decent quality of service without breaking the bank. It is a full-grown discipline with its specialized training, books, professionals, etc.

Don't expect that WLAN can work magically without a similar effort.

Re:Directional access points (1)

coryking (104614) | more than 5 years ago | (#24810901)

Dont forget their protocols are optimized for this kind of thing whereas 802.11 is not.

Further dont forget that cell phone calls are like a really long running, slow speed transmission whereas web traffic is high bandwidth transmissions in short bursts.

On top of that, dont forget TCP/IP *hates* mesh networks and *hates* you hopping around on one. All the wireless protocols either have to deal with you moving from access point to access point or they just ignore the problem and not let you roam.

Don't expect that WLAN can work magically without a similar effort.

People pull it off, but it ain't with 802.11 for starters. It is with much more expensive proprietary gear that deals (er, hacks around) the shortcommings of TCP/IP. Even then your link will never be as reliable or as fast as a wired one.

You got that backwards (1)

George_Ou (849225) | more than 5 years ago | (#24812799)

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.

Re:Directional access points (1)

ploxiln (1114367) | more than 5 years ago | (#24826623)

I interned for a company named "Xirrus" this past summer; their primary product is similar to what you describe. It's an "Array" of directional access points in a radial pattern, each access point running on a different channel in the 5GHz band (802.11a). These things are pretty expensive and mostly sold to universities, airports, etc, but they work pretty well... Actually I just noticed that Xirrus was mentioned in TFA. Anyway, if you want a look at the inside of one of these things, see here: http://xirrus.com/products/arrays.php [xirrus.com]

Article in latest ;login: (2, Interesting)

erikdalen (99500) | more than 5 years ago | (#24808633)

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 [usenix.org]

Re:Article in latest ;login: (0)

Anonymous Coward | more than 5 years ago | (#24809057)

I started the read on this - don't really see what is "unique" here.
In Cisco parlance you are talking about LWAPP with RRM.
I know Meru does the same thing too as does Avaya

Just throw a bunch of APs up with non-overlapping channels in the A band and set maximum number of clients per AP ..

I have 699 radios at my work ( just waiting to break 700 :) ) and we typically put 6 APs in a rectangular area 75 feet wide by 175 long ) or about 2100 square feet per AP. That is a radius
of about 26 feet. The 802.11B/G we can't really help channel-wise but 802.11A .. wow, we can overlap those puppies like the dickens and not have co-channel interference.
So we try to get Medical Devices to use "A" and weird devices to use B or G if they can.

WHAT? (0)

Anonymous Coward | more than 5 years ago | (#24808677)

Who uses Wifi but other than....oh wait....

The reason of the sourge (1)

eiapoce (1049910) | more than 5 years ago | (#24808817)

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.

man'kind' facing huge challenge to survival (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#24808909)

it's not the 'weather' (which is going to be challenging enough), it's more about failing to disempower the fauxking life0cidal corepirate nazi execrable, who have placed themselves above/in charge of, us. fear is unprecedented evile's primary weapon. that, along with deception & coercion, helps most of us remain (unwittingly?) dependent on its' greed/fear/ego based hired goons' agenda. Most of yOUR dwindling resources are being squandered on the 'war', & continuation of the billionerrors stock markup FraUD/pyramid scheme. nobody ever mentions the real long term costs of those debacles in both life & the notion of prosperity, not to mention the abuse of the consciences of those of us who still have one. see you on the other side of it. the lights are coming up all over now. conspiracy theorists are being vindicated. some might choose a tin umbrella to go with their hats. the fairytail is winding down now. let your conscience be yOUR guide. you can be more helpful than you might have imagined. there are still some choices. if they do not suit you, consider the likely results of continuing to follow the corepirate nazi hypenosys story LIEn, whereas anything of relevance is replaced almost instantly with pr ?firm? scriptdead mindphuking propaganda or 'celebrity' trivia 'foam'. meanwhile; don't forget to get a little more oxygen on yOUR brain, & look up in the sky from time to time, starting early in the day. there's lots going on up there.


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corepirate nazi execrable costs outweigh benefits
(Score:-)mynuts won, the king is a fink)
by ourselves on everyday 24/7

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& pretending that it isn't happening here;

all is not lost/forgotten/forgiven

(yOUR elected) president al gore (deciding not to wait for the much anticipated 'lonesome al answers yOUR questions' interview here on /.) continues to attempt to shed some light on yOUR foibles. talk about reverse polarity;


The real issue here is this. (3, Interesting)

jskline (301574) | more than 5 years ago | (#24809095)

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.

Re:The real issue here is this. (0)

Anonymous Coward | more than 5 years ago | (#24809265)

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.

That is incorrect. 802.11g uses exactly the same bands as 802.11b. The increased throughput is the result of a more computationally intensive encoding which uses the spectrum more efficiently.

Re:The real issue here is this. (1)

coryking (104614) | more than 5 years ago | (#24810951)

This might sound like a dumb question... but these improvements to the protocol (er encoding) were basically the result of improvements to the speed of the hardware? In other words, then 802.11b came out, they could have use the same kind of encoding as 802.11g but it would have cost too much? Or did some smart dudes sit around and dream up a more efficient way to use the same spectrum using basically the same hardware as before?

Re:The real issue here is this. (1)

sn00ker (172521) | more than 5 years ago | (#24817779)

Or did some smart dudes sit around and dream up a more efficient way to use the same spectrum using basically the same hardware as before?

Yeah, pretty much. As someone else said, b uses a different modulation to g. The change from DSSS [wikipedia.org] to OFDM [wikipedia.org] was mostly about more-efficient use of spectrum, without utilising more of the spectrum.

Re:The real issue here is this. (1)

coryking (104614) | more than 5 years ago | (#24811003)

Oh, and one more question since one of you know the answer. When I was trying to get my Sage Media Extender (SageTV = MythTV only better, Media Extender = a standalone client for your TV), it could do 802.11g but their manual and wikipedia clamied that once my 802.11b laptop got on the same access point, the access point would degrade everything to 802.11b. Is this true? ... I gave up trying and just ran Cat5e to the box though. 802.11 anything just doesn't like it when you skip around MPEG streams. You'd get all kinds of compression artifacts for a second or two after skipping because the box couldn't fill its buffer fast enough.

Re:The real issue here is this. (0)

Anonymous Coward | more than 5 years ago | (#24812393)

802.11g access points usually operate in a compatibility mode which allows 802.11b clients to participate in the network. That compatibility mode extends the duration of certain signals so that the slower cards can recognize when the channel is in use. This mode is therefore slightly slower than the 802.11g-only mode. An additional slowdown occurs when 802.11b clients send or receive data, because the transmission takes more time at the slower rate of that client. In the time in which an 802.11b client can send or receive one packet, an 802.11g client could send or receive about four packets. As long as the network isn't saturated, neither effect is problematic.

Re:The real issue here is this. (1)

louarnkoz (805588) | more than 5 years ago | (#24810629)

Actually, the progress from B to G and then N correspond to specific improvements in the radio. B uses "direct sequence" modulation; G (and A) use OFDM, which is more efficient and allows for greater throughput; N uses MIMO, which roughly multiplies the bandwidth of the channel by adding antennas and radios, in the same band.

Well duh... (2, Insightful)

BlueParrot (965239) | more than 5 years ago | (#24809387)

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.

Re:Well duh... (1)

drwho (4190) | more than 5 years ago | (#24810557)

When you say frequency, I believe you mean spectrum, or bandwidth.

Re:Well duh... (1)

zippthorne (748122) | more than 5 years ago | (#24811495)

No, he means the carrier frequency. or perhaps just band.

If your bandwidth is 10% of your carrier frequency (quite a lot, actually, and the bigger the percent, the less gain you're gonna get on your antenna), then a 60hz carrier will be like 6 baud. Not a very high data rate, even with quadrature.

a 6Ghz carrier however...

They say use text instead of voice (0, Offtopic)

alta (1263) | more than 5 years ago | (#24809897)

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.

Need more spectrum! (1)

drwho (4190) | more than 5 years ago | (#24810533)

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.

traffic shaping / bandwidth throttling (1)

NynexNinja (379583) | more than 5 years ago | (#24810677)

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.

abandon slower rates (2)

drwho (4190) | more than 5 years ago | (#24810875)

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.

Larger spectrum and adaptive software... (1)

PCMeister (837482) | more than 5 years ago | (#24811905)

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...

Not enough coffee... (1)

Rick Genter (315800) | more than 5 years ago | (#24812033)

I saw the headline and thought "What? Wireless LANs and face-huggers? Huh?"

Definitely need more coffee...

Scaleable Wireless LANs (1)

agrisea (877522) | more than 5 years ago | (#24816127)

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.
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