Bluetooth vs. Infrared

Most of the modern cell phones are equipped with both “Bluetooth” and “Infrared”. “Bluetooth” is extremely popular these days. But “Infrared” also has its use. The other day I was reminded of this.

My brother and I were in the car on the highway between Paphos and Limassol. I was driving at about 140 km/h. My brother was occupied copying ringtones from my SonyEricsson P800 onto his SonyEricsson P910. “Bluetooth” connection wasn’t working at all. When I slowed down to about 80 km/h it managed to connect, but was very slow and unstable. “Infrared” on the other hand, worked like a charm.

I suspect that this was because “Bluetooth” is a point-to-multipoint connection. Basically, it is like a small radio transmitter. It sends waves to about 10 meters around it. Because the car was moving so fast, it was getting out of the 10 meters radius pretty fast. “Infrared” on the other hand is a point-to-point connection. As long as it can “see” the other end, the connection will work perfectly.

21 thoughts on “Bluetooth vs. Infrared”

  1. Wow :) Even if the light speed was as little as you car’s speed, the radio waves from your phone would have the same along-the-road speed component as your car because they were emitted from the moving object – the phone in the car. One of the phones was stationary in relation to the other, and so the speed your car was moving at could not have any impact.
    If you threw a ball at your brother, he would catch it whatever speed you are driving at :)

    In addition, the light speed was 128482 times higher than your car’s so even if the theory above wasn’t right, your car’s speed wouldn’t have any impact on the connection quality either.

    The phenomenon you described was probably a co-incidence.

  2. 1. If I through the ball at my brother, that would be a point-to-point connection.

    2. What does the speed of light has to do with radio waves? :)

    3. Why does Bluetooth connection works perfectly between the same two phones in a stationary car?

  3. 1) Forget about your notion of p2p versus broadcast, it has no value here. It does not matter in what direction the phone emits bluetooth electromagnetic waves or infrared electromagnetic waves or anything else as long as this direction includes the recipient.
    2) You really should have listened to your teacher of physics at school. Both light and radio waves are same electromagnetic waves, just of a different frequency. Hence, radio waves travel at a speed of light.
    3) My version is that was a coincidence. Try again before making scientific conclusions.

  4. A realistic yet unlikely explanation would be that the phone was trying to connect to other bluetooth phones in cars nearby, but because they were disappearing from the 10m radius quickly, the phone was retrying for some time, and probably this was affecting the connection quality to the nearby stationary peer.

    Read this page about the light as an electromagnetic wave:

    Red light : 428 570 GHz
    Infrared : 3000…400000 GHz
    Bluetooth : 2.45 Ghz

  5. No, I don’t think so. First of all, it was the intercity highway, so the number of cars on the road wasn’t so large. Plus, I was passing them pretty fast, as I was driving at 140+ km/h. Plus, Bluetooth, although popular, is not that widely used yet.

    There must be another explanation… :)

  6. LOL it’s really funny guys :D


    How you got 128482 times faster? The light speed should be 7 714 285 times faster than Leonid’s car.
    light ~ 1080 Mkm/h, car ~ 140 km/h


    I always like your car, now especially. :D

  7. Let’s flame begun! :D

    Alexey, I don’t know, I calculate like:

    84 [km] / 300000 [km/sec] = 0.00028 [sec]

    But actually, it doesn’t matter after that kind acceleration. Poor, poor Leonid and his car, we will never find them. Poor people of the earth, we will never see them again, after annihilation ~ 2 tons of matter. God forgive us :D

  8. Long live the flood!

    Yes, the light would get to Nicosia in 84km / 299792.458kms = 0.00028s. But we were talking about Leonid’s car which I erroneously declared as running 128482 times slower than the light, while in reality it is 7708949 times slower. My error accelerated Leonid and his brother so that they were able to get to Nicosia in 84km / 140kmh / 60 = 36s. Thirty six seconds. Which is not bad anyway for a used Mitsubishi Galant.

  9. Just wondering which connection speed is faster?

    Bluetooth or Infrared?

    And it was instances whould u want to use bluetooth and not infrared and vice versa?


  10. there was a weak connecton on the highway because the radio waves were not able to propogate well enough(lack of objects). as the bluetooth device works on the principal of radio waves hence it was not able to connect properly(lack of signals).

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