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Has 2.4 GHz Reached Maximum Capacity?
An anonymous reader writes "There's been a lot of talk lately about the concept of Personal Area Networks. At CES Intel and Connectify both released software that turns Windows laptops into Access Points for file transfers, wirelessly syncing pictures from cameras, and Internet sharing. This is good, maybe great, if you're a road warrior, but what about the rest of us holed up in apartment buildings and small neighborhoods? We already have to deal with the wireless chatter of the 50 or so other Linksys routers in the vicinity. What will happen when every laptop also acts as a software router? To add fuel to the fire, Intel and Netgear also announced the Push2TV device that allows you to stream your display, including Netflix videos straight to your television. Isn't this going to kill lower powered 2.4 GHz devices, like Bluetooth mice and headsets? When does the 2.4 GHz band collapse completely? Why can't we push all this short range, high bandwidth stuff onto 5 GHz?"
Pretty much every manufacturer sets the default power output levels to FUCKING LOUD. This means that I can get a clean signal from your router 100m away. Worse yet, most channels have overlapping frequencies with one or two of their neighbours on either side.
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Go canucks, habs, and sens!
God help you if you want to use your microwave. You'll kill the connection to every device in your house.
"Tell me doctor, with all of your defenses, are there any provisions for an attack by killer bees?"
Tip: Verizon also defaults their routers to using WEP. I would really consider not paying for internet if I were you... Think of it this way, it will be one less AP being used which makes it more pleasant for everyone involved.
"linux is just DOS with a UNIX like syntax" -- Galactic Dominator (944134)
If you're in a place with too much WiFi noise, try using the Japanese-only channel 14 - it doesn't overlap with any other channels, and you're pretty much guaranteed to be the only person using it. DD-WRT and other alternative firmwares will broadcast on 14, and Windows just requires a simple registry hack to receive on 14. Macs, I believe, can connect without hassle. It's technically illegal, but the likelihood of being caught is pretty much nil. I've still never found an explanation for what this frequency is used for in the US, if anything.
Router? I never ever met 'er.
Since I _don't_ deal with a lot of Windows PCs, I _am_ running everything on 5.0 GHz. Well, OK, there's a "guest WiFi" at 2.4 GHz for friends, but I don't care if that's broken.
Most PCs I've seen with 802.11n only have the 2.4GHz support, and same with a lot of add-on cards and access points. The dual-band stuff is starting to be a little easier to get, though still a bit of a price-premium. Of course, since my machines are either Macs on Wi-Fi or Linux on gigabit copper, I'm already used to a price premium.
However, there's a good side effect of this: a certain eggy on-line store had a whole bunch of refurbished Netgear 5.0 GHz _only_ access points/bridges on for less than $40. So the couple of devices I have that don't do WAP and/or don't do 5.0 GHz are now using those things. Similarly, I set up a friend's office to use one so his Macs aren't drowned out by all the 2.4 GHz chatter in the area. (Downtown, right beside a condo and hotel, across the road from an office building... and almost everyone on channel 1, too.)
Heck, $40 is less than the price of a USB 802.11n adapter. So I bought a couple extra just in case.
So, if everyone else would just _stay off_ 5.0 GHz, I'll be very happy.
Yup, none of the access points are actually smart enough to switch channels and optimize frequency/power usage. So you end-up with the problem I encountered this December, when a neighbor across the way got a wireless router, and suddenly my internet stopped working. You couldn't even *see* my access point anymore, it was just overpowered.
My access point configuration was set to "Auto," but this just meant it kept trying to use channel 1 like an idiot. So I forced it to use channel 6, and the problem was solved.
But this isn't how things should be. The devices and the protocol should be smart enough to optimize spectrum, both by analyzing the noise at various frequencies and choosing the band with the least automatically, and by playing nice with other devices and dialing-down the power to that needed by the connected device furthest from the access point.
Too bad the above is just a pipe dream. I can't imagine how bad it is living in dense residential/apartments, where these users still don't know how to configure things, but there are 2 dozen within range instead of 5.
Man is the animal that laughs.
And occasionally whores for Karma.
Ah yes, the quaint wire: Your own personal air domain, a veritable Ether network. Copper's getting scarce and we'll never run out of glass, but optical transceivers are still thousands of dollars. It's getting cramped on this little planet!
slashdot: where everyone yells sarcastic metaphors to themselves to understand the issue
Boom! Headshot.
Yup, none of the access points are actually smart enough to switch channels and optimize frequency/power usage. So you end-up with the problem I encountered this December, when a neighbor across the way got a wireless router, and suddenly my internet stopped working. You couldn't even *see* my access point anymore, it was just overpowered.
My access point configuration was set to "Auto," but this just meant it kept trying to use channel 1 like an idiot. So I forced it to use channel 6, and the problem was solved.
But this isn't how things should be. The devices and the protocol should be smart enough to optimize spectrum, both by analyzing the noise at various frequencies and choosing the band with the least automatically, and by playing nice with other devices and dialing-down the power to that needed by the connected device furthest from the access point.
Too bad the above is just a pipe dream. I can't imagine how bad it is living in dense residential/apartments, where these users still don't know how to configure things, but there are 2 dozen within range instead of 5.
That all works in my favor. Nearly everyone in my complex has their router set to channel 6 or something. I set mine to channel 1 and I've got all the reception I could ask for!
-Taylor
Worldwide Military budgets: $2100 billion. Worldwide Space Exploration budgets: $38 billion. Really, world? Really?
It is fun to watch a spectrum analyzer when someone fires up a microwave. Old cordless phones are entertaining too. One is a multi-megaton nuke, the other a tac-nuke.
Doesn't 802.11n come with the option of being in 5GHz
You'll be comforted to know that ZigBee devices, and other devices that conform to the IEEE 802.15.4 standard, do this today, and have done so since 2003.
The second part of your wish, that devices dial-down their power to the minimum needed, is certainly possible, but requires that the receiving device send an RSSI (Received Signal Strength Indication) or, better, an RQI (Received Quality Indication) value back to the transmitting device (perhaps as part of the ACK), and that the transmitting device be capable of lowering its transmit power in the first place (it's an extra expense). I don't know of any protocol that does this (other than CDMA protocols, for a different reason), although I expect newer protocols will -- but to save power (extend battery life), not to reduce spectral pollution.
The problem is dumb receivers, not lack of spectrum.
Channel capacity is determined by the MIMO form of Shannon's Theorem. Add more antennas and smarter processing in the receivers, and the capacity in a channel with lots of multipath (eg. in an apartment) increases approximately linearly.
The problem is that most hardware is a decade (or more) behind state of the art, and that people aren't prepared to pay for a more complex, and costly receiver.
Wifi Troubleshooting with an analyzer tool.
http://www.youtube.com/watch?v=8eOByjhx2oY
http://www.youtube.com/watch?v=MG48woHjzko
The first is 6 minutes introducing the app. The second shows some waveform stuff.
The theoretical max for wireless G is 27.4 Mbps. Reading a DVD at 1X is 10.5 Mbps. As I understand it, when you are transmitting from one wireless device to another, you are talking to the AP which then retransmits to the other device, effectively doubling your data.
So, starting with 10.5Mbps then doubling the data and adding overhead, you are dangerously close to the theoretical 27.4Mbps max.
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http://en.wikipedia.org/wiki/IEEE_802.11n-2009
Coupling MIMO architecture with wider bandwidth channels offers increased physical transfer rate over 802.11a (5 GHz) and 802.11g (2.4 GHz).
Besides the FCC specs that WiFi devices meet (which are really a fairly bare minimum to avoid really crappy interference), manufacturers take some time to make sure their devices behave. You can be certain Cisco pays attention, and other well-regarded makers, because they intend for their enterprise clients to deploy these in a mesh and will definitely suffer if they are out of spec.
Now, there are plenty of shady outfits, but since everyone pretty much uses the same few radio chipsets, the makers of those chips do their work and produce decent product. No one wants to take back a few thousand routers because they suck so bad they can't live with anything. Besides, does anyone buy D-Link routers any more after their NNTP fiasco? Well, actually, we have short memories, and there is fresh meat being minted every day.
Claiming this is a technical failure by the manufacturers is bogus. More likely, the WiFi spec doesn't really accomodate an infestation of routers. There just aren't enough channel spacing options to solve this in WiFi, and I doubt there is a fix beyond a new spec.
Hey, that's it, call IEEE! We need a new 5GHz or higher spec, dudes. We can wait 4 or 5 years. get on it, ok?
Not that going to higher bandwidth will solve range problems. It's a morass of options and expectations.
deleting the extra space after periods so i can stay relevant, yeah.
Anyone can get your WEP key with just a handful of minutes and a tiny bit of know-how. If someone knows enought to try changing its settings to make it better suit their needs, you can be sure they can crack your WEP key. Cracking WEP networks is particularly easy, and useful if you live next to the network in question.
Seriously people, stop using WEP unless you actually understand the consequences and can make an informed decision to ignore them.
Also, ethernet and wifi are significantly different beasts (though DVD quality probably shouldn't be an issue.)
"linux is just DOS with a UNIX like syntax" -- Galactic Dominator (944134)
Well, not quite all of them. One of the main benefits with tinkering with DD-WRT on Linksys b/g hardware is being able to boost the output from the rather puny(but effective for most) factory 28mW to well over 200mW. Makes for some pretty expansive WDS setups, and a HELL of a lot cheaper than the higher end commercial hardware.../i.
DD-WRT's power settings are great. For setting the power level lower...
Don't use them to set the power levels higher than the chipset's specs. The signal to noise ratio drops. You're just sending out the same data, louder, but with a correspondingly increased amount of background noise. You're not improving your connection, and damaging everybody elses'.
After all, I am strangely colored.
"Why can't we push all this short range, high bandwidth stuff onto 5GHz?"
I really wish you wouldn't. I prefer to keep the 5GHz band wide-open for the unimpeded use of my own 5GHz devices. I bought them specifically to avoid 2.4GHz clutter!
...And currently, it's 2.4 GHz.
Before that, it was the 900 MHz band -- until it filled up with cordless crap.
As others have posted, 5 GHz is still pretty clean, so use it while you can. In our residential area, 2.4 GHz is full (even 14 is in use), but there's little activity on 5 GHz, so that's where our macbooks connect.
Same at work -- dual mode phones, bluetooth, microwave ovens, old laptops and more all on 2.4, with the newer equipment connecting on 5 GHz.
I had been using wireless and just wired my house so that I didn't have to worry about neighbors blasting my signal any more.....it's not hard. Lifehacker had a pretty good write-up back in Nov/Dec time frame.
A laptop that sits on a desk 24/7 (like most of them do) isn't being used as a portable device and doesn't need wireless in the home. If you can plug in a power connector you can certainly plug in an ethernet cable too. Heck, a docking station even takes care of that for you.
Personal Area Network describes the relative distance between each device on the network as it relates to the individuals or groups it is connecting. It does not refer to how those devices actually connect in any way. A PAN is basically a network of one individual's personal devices, which is kept distinct from wider area networks like a LAN or a WAN. The term itself has no relation to any particular technology, it's just a designation for a type of network.
A PAN is one step more intimate than a LAN, which is in turn one step more intimate than a WAN. You can and do have PANs with wired connections instead of wireless. Any time you connect a personal organizer or smartphone to your laptop, for example, you've created a PAN.
As we use more and more of these devices and as more of them use wireless technologies of various kinds, it makes sense to make the "hub", which is usually an ordinary PC, act as a router among among the different personal devices.
An ad-hoc wireless network refers to setting up a peer-to-peer wireless LAN, which by definition is not a PAN.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
Look, I get it and all, if you were the next ridge over and pointed your Pringle can Yaggi antenna directly at my house and then decided to start cracking my WEP key you will gain access to my pron and all my base would belong to you! congrats :)
It's my freaking home DSL connection, with two iPod Touches a laptop and my torrent/media box. BTW the crappy VZ DSL router does do MAC filtering so you'd need my WEP key and spoof a MAC... and if you're ever out this way, just knock and I'll let you in, have some tea and you can use my wifi.
http://teasphere.wordpress.com - A little spot of tea
The IEEE-802.15.4 specification defines a way to reduce power, but it does not enshrine this at the MAC layer of this protocol. Perhaps Zigbee may do this, but it isn't in '15.4 as far as I have read.
The feature you're talking about is called Clear Channel Assessment (CCA) and it is part of ,most of the wireless specifications. The problem with CCA is that the threshold is shockingly low. And what you hear at the transmitting end isn't necessarily what the receiver hears. In other words, the receiver could be trashed by another signal too far away for you to hear. I need to remind everyone here, this is not a coaxial cable or a fiber system. It is radio. Radios wave systems are not perfect hubs or trunk lines. There are signals on the air that one side may hear that the other doesn't.
Another issue you might not realize is that it takes at least as much power to run an 802.15.4 receiver as it does the transmitter. In most cases, the the transmitter is the local oscillator as well. There isn't much power to be saved.
So why reduce power? To reduce the chance that a signal can be received by others with nefarious intent, and to reduce interference as you said.
I suggest people consider using different channels. Even though the 802.11 channel passband is over 22 MHz wide, and there are really only three channels that don't overlap, you can still choose an adjacent channel and use the despreading to your advantage.
I find that the default channel for most of 802.11b/g routers is channel 6. Use anything but that and you'll probably do OK. Those who can remember the heyday of CB radio, may remember that most of the kiddie walkie talkies used to be on CB channel 14. That was the one channel you didn't want to be on. It is interesting that we still haven't learned that lesson even today.
Nearly fifty percent of all graduates come from the bottom half of the class!
Most people don't have ethernet in every room though. Since the router often has to be in a certain place (i.e. where the phone line comes in) wifi to the office/bedroom makes sense. In fact that is supposed to be one of the biggest benefits of wifi.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
As you get to the end of the range noise is generally dominated by receiver noise, interference etc not by transmitter noise (which don't forget is attenuated as much as the signal)
So I would expect cranking up the power to increase range unless the transmitter gets so noisy that even a close-by receiver is having trouble.
Still use it wisely and watch out for the FCC ;)
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register