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Wireless Networking Communications Intel

Has 2.4 GHz Reached Maximum Capacity? 250

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?"
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Has 2.4 GHz Reached Maximum Capacity?

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  • by Goalie_Ca ( 584234 ) on Wednesday January 27, 2010 @05:12PM (#30924712)
    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.
  • Re:Apartment Wifi (Score:3, Interesting)

    by Sir_Lewk ( 967686 ) <> on Wednesday January 27, 2010 @05:20PM (#30924864)

    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.

  • Re:Channel 14 (Score:3, Interesting)

    by dattaway ( 3088 ) * on Wednesday January 27, 2010 @05:59PM (#30925650) Homepage Journal

    The Atheros wifi card in my Acer One can cover 2.1-2.8GHz, in 58 channels with a simple config. But I won't do it, because all kinds of things in the sky use slices of those frequencies.

  • by Anonymous Coward on Wednesday January 27, 2010 @06:13PM (#30925946)

    Wifi Troubleshooting with an analyzer tool. [] []

    The first is 6 minutes introducing the app. The second shows some waveform stuff.

  • Re:Apartment Wifi (Score:1, Interesting)

    by Anonymous Coward on Wednesday January 27, 2010 @06:15PM (#30925972)

    Take a small linux box, add 4 wireless adapters to it, and wire all your other computers to it.
    Map all the wifi hotspots in your building and crack the keys. Divide that into 4 lists.
    Assign each adapter to a list of available routers, so if one goes down it will swap to the next in the list.

    Load balance across the 4 adapters and leech more bandwidth than you'd ever need.

  • Re:aircrack (Score:1, Interesting)

    by Anonymous Coward on Wednesday January 27, 2010 @06:23PM (#30926120)

    If you see a 2wire* network available you have free internet.

    Not always. My network is called 2WIRE*, but it isn't really one. If you assume my hex key is 0-9 only, you'll never crack it. If you do crack it, you'll find other problems getting access or even sniffing traffic. But yes, normal 2WIRE* routers are fairly insecure.

  • by poopdeville ( 841677 ) on Wednesday January 27, 2010 @06:39PM (#30926424)

    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'.

  • by cdrguru ( 88047 ) on Wednesday January 27, 2010 @06:43PM (#30926502) Homepage

    You are missing the fact that inherently there can only be one transmitter on at a time within a given physical space.

    You might be able to expand the physical space beyond the transmitter's range and call that having two transmitters in the same space - but that isn't the point.

    There are some tricks with polarization that can be used, but these are not currently being done and are basically incompatible with the omnidirectional nature of most uses of the 2.4Ghz frequency.

    Anything beyond one transmitter at a time is just a collision and nobody gets their message through. Current 2.4Ghz uses account for this and accomodate it - by retransmitting. Sooner or later you are going to run into the situation where there are enough "talkers" there are no more open time slots for a new transmitter to move into. Once this happens you get higher and higher percentages of collisions

  • Re:The problem (Score:3, Interesting)

    by SQLGuru ( 980662 ) on Wednesday January 27, 2010 @07:08PM (#30926976) Journal

    I had been using wireless and just wired my house so that I didn't have to worry about neighbors blasting my signal any's not hard. Lifehacker had a pretty good write-up back in Nov/Dec time frame.

  • Re:Ad Hoc Networks (Score:3, Interesting)

    by Bigjeff5 ( 1143585 ) on Wednesday January 27, 2010 @07:16PM (#30927082)

    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.

  • by AB3A ( 192265 ) on Wednesday January 27, 2010 @08:18PM (#30927804) Homepage Journal

    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.

Neutrinos have bad breadth.