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Advantages and disadvantages of Radio and Infrared communications

Posted on 2007-04-03
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What is the Advantages and disadvantages of Radio Frequency communications  vs. Infrared communications.  For example Bandwidth, FCC Regulation, Interference and eavesdropping
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Question by:pgagnon1960
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jamiejolliffe earned 168 total points
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The FCC does not have any regulations regarding Infrared communications, unless the IR device also emits radio energy. Refernence: http://www.electrical.bureauveritas.com/fcc-faq.html
Radio Frequency devices, however, need to be operated in accordance with the FCC.

Bandwidth would depend on the actual IR/RF devices being used.

Interference could be an issue with either technology, IR mainly due to ambient light or any obstruction in the light path, RF due to other RF emitting devices.

Eavesdropping would likely be more difficult with IR as one  would need to be in the actual light path to have a signal.  RF, however, can use technologies such as spread spectrum (aka. frequency hopping) to make eavesdropping more difficult, as well as to protect against interference.
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by:cyberpranav
cyberpranav earned 166 total points
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1. Practically the bandwidth for RF communications is more than in IR.

2. There are no FCC regulations for IR, until the device may cause any noticable interference to RF
    devices in the vicinity. There are FCC regulations for RF communications and you will find those if
    you do a google search.

3. There may be interference in RF communications, but its difficult in IR.

4. Eavesdropping is possible in RF communications, but very difficult in IR.

::Pranav::
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by:fwecoadmin
fwecoadmin earned 166 total points
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RF can go through most walls and is less susceptible to interference by physical obstructions.  NOTE: If your wall is a bank vault, an elevator or made of copper mesh, all bets are off.  I’m talking about standard drywall or your average brick wall.

Given an equal amount of power the RF seems to achieve control at further distances.  Though this is based purely on observation and I have no empirical data to back this up.  If anyone takes issue with it I can respect their opinion and may even be swayed to change my view on this.

However RF may be affected by other items that may be transmitting at the same RF such as a phone on 931.8125 MHz and a garage door opener at the same freq.  Another example is the proliferation of cordless on the 2.4 G and many WiFi devices on the same 2.4 G frequency.  This can cause noticeable audio interference on calls and latency (delay) on your WiFi network due to packet loss… “if there are any other devices operating on the same channel, as interference will cause packet loss” http://www.smartbridges.com/support/faq_ab.asp


There are also limits as to how high your Db level can be set.  I recall the limit being 30Db gain for 2.4G with a 12 DBi antenna going point to point on a backhaul for a WISP. Whatever the exact numbers, you get the idea.  The FCC has regulations in the USA and you can’t just put a 12 foot parabolic with a ludicrous Db and cook your neighbors.  See the following for a chart: http://www.dailywireless.org/2005/07/31/new-wifi-record-125-miles/

Obviously IR is not affected by any other RF devices within your house or office.  However it does seem to require a good line of sight with few or no obstructions and seems to work less effectively when working on greater angles.  You can’t change channels from the basement to the living room and it seems to pose a problem for those Sales guys giving presentations on a screen and insist on pointing at the image instead of the projector about 25 ft in the opposite direction.  However this can be rectified by reflecting the IR with mirrors. Yes mirrors will do it.  Some people state that extremely bright daylight will affect a difference and I have noticed that if you are trying to change something behind smoked glass it will also have a detrimental effect.

Eavesdroping on WiFi? Are you kidding me?  Man you can sniff out, spoof and use anyone’s WiFi given enough time and tools.  Without going into much detail, WEP encryption ain’t no thang.  Although some of the new standards of encryption that we are seeing in off the shelf WiFi routers are getting harder.  Legions of kids are pirating their neighbors WiFi internet and with the right tools they can intercept and decrypt the contents of what is being sent.

Regarding IR eavesdropping I will quote the following:  “infrared is generally considered to be more secure to eavesdropping, because IR transmissions require absolute line-of-sight links.”  From http://nislab.bu.edu/sc546/sc546Fall2002/NS80211/howto.html
However I’ve not known a single person to hack their neighbors IR connection while they were changing the channels to HBO.  Though this could prove useful in changing the TV channels at the local Pub you may frequent.  Also see: http://www.niksula.cs.hut.fi/~jpmyyry/tlark/05/index.html.  Known Vulnerabilities in Wireless LAN Security.  This is an old paper but gives a brief answer to this in part 2 Means Of Comunications.


I don’t know much about the wavelength ranges of IR but I would recommend the simple chart on Wikipedia: http://en.wikipedia.org/wiki/Infrared

Bottom line is I prefer RF over IR and have replaced most controls with to favor RF wherever possible.
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