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Non Line of Sight Broadband

Posted by CmdrTaco on from the wouldn't-it-be-nice dept.

gfilion writes "IEEE Spectrum has an article about nifty wireless adapters that don't require LOS. At first, NLOS wireless may not sound like a big deal. After all, ordinary radios and cellphones are non-line-of-sight devices. But they don't carry broadband data. What makes the latest generation of NLOS wireless technology worth talking about and having is that it delivers data at high rates over substantial distances."

8 of 168 comments (clear)

  1. ordinary radios ...are non line of sight by wiredog · · Score: 2, Informative

    Actually, FM radio is line of sight.

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    1. Re:ordinary radios ...are non line of sight by Salden · · Score: 2, Informative

      Really? Then how come I can receive FM radio in my basement behind cinder block?

    2. Re:ordinary radios ...are non line of sight by Lumpy · · Score: 5, Informative

      Not. not by a long shot.

      FM is Frequency Modulation. it is a mode of transmitting. what you are talinkg about FM or the 88-108Megahertz broadcast band, is not line of sight. that low of a frequency has both ground waves and sky-waves. this is how in west michigan I can recieve WLUP Chicago on 97.9MHZ easily by swinging a directional gain antenna in that direction. Also, Frequencies from 88MHZ up past 450MHZ also can take advantage of tropospheric ducting.

      Line of sight doesn't start until past 1.2 GHZ 802.11 equipment at 2.4ghz act like line of sight outside because of water vapro and water bearing items (leaves, squirrels, children) suck up large amounts of signal..

      so NO FM is not line of sight. not in the correct term nor in your definition.

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    3. Re:ordinary radios ...are non line of sight by Muad'Dave · · Score: 3, Informative

      Modulation schemes have nothing to do with whether a particular transmission is line-of-sight or not. Carrier frequency does. I assume by "FM radio" you mean commercial broadcast FM as in 88-108 MHz. Why then was I receiving 96.5 WFLB (which is in Fayetteville, NC) in Richmond, VA the other morning (which has a 96.5 of its own)? Hint - Tropospheric Ducting (or tropo-ducto, as I call it, since it's nearly indistinguishable from magic - presto-chango and all that).

      In general, as frequency increases, so does the line-of-sight nature of the RF. Light, being extremely high frequency RF, is very much line-of-sight. AM Radio, being between 540 kHz and 1600 kHz, can span the globe because of groundwave bending and ionospheric ducting. Amateur radio operators deal with lots of different propagation modes all the time.

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    4. Re:ordinary radios ...are non line of sight by client32 · · Score: 2, Informative

      When "line of sight" is used for FM stations it means that the signal can only carry to the horizon. Meaning your radio station would can only broadcast as far as you can see from the transmitter. This has to do with the type of wave, the fact that the earth is round, and the atmosphere. There are several website that discuss this. Search google for it.

      I hope that this clears up some confusion.

    5. Re:ordinary radios ...are non line of sight by Cmdr+Taco+(luser) · · Score: 2, Informative

      The best way of saying it...

      FM radio is more line-of-sight than is AM radio. But of course line-of-sightedness is a characteristic that has absolutely nothing to do with the modulation method but everything to do with carrier frequency. The higher the frequency, the more line-of-sight it is. Consider light, which is very line-of-sight.

      FM = Frequency Modulation in which information is encoded by varying (modulating) the frequency of the carrier.

      AM = Amplitude Modulation in which information is encoded by varying the amplitude of the carrier.

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  2. Mod this up by metatruk · · Score: 2, Informative

    Wiredog's right.
    FM broadcast radio, as well as cell phones, and broadcast television work in the VHF and UHF bands.
    Because of the frequency of the carrier wave, these bands propagate using line of sight which means that the signal's means of propagation are not by reflecting off of something such as the ground or sky.
    Lower frequencies, such as local AM broadcast use ground wave propagation, because the signal reflects off of the ground.
    Short wave radio tends to propagate using sky wave propagation, because the radio signal bounces off of the earth's ionosphere. This is often refered to as "skip" and can cause signals to travel across the globe.

  3. Re:Noone wants broadband? by scott1853 · · Score: 3, Informative

    I work for an ISP in a rural area. People call up all the time because they signed up for AOL and then they got their first phone bill and... you know the rest. But quite a few actually insist on keeping their AOL service even though we provide the same thing but without the flashy software with the "you got mail" WAV file. So they're will to pay us $18/month and whatever AOL is charging for an outside ISP account now ($10?).