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Bluetooth & X-Bee Distance Considerations — Parallax Forums

Bluetooth & X-Bee Distance Considerations

Bruce BatesBruce Bates Posts: 3,045
edited 2007-05-22 15:23 in General Discussion
Folks -

Would any of you fine·people who have had experience with Bluetooth and/or X-Bee care to comment on the distances one can expect from such systems?

Do general RF considerations apply as far as interference, and best transmission practices, or are there any special or unique considerations?

Are multiple channels available with either system?

The planned application needs a bi-directional (half duplex) wireless connection, and I'm trying to avoid the cost of cellular if I possibly can. It may or may not require multiple channels.

Thanks in advance.

Regards,

Bruce Bates


Post Edited (Bruce Bates) : 5/16/2007 8:18:37 PM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-05-16 18:18
    xBee is rated for about 300 feet line of sight range. If you go to an xBee-PRO, they're rated for about a mile. They have the same interference issues as other 2.4GHz devices. There are a lot of them around and there are a lot of microwave ovens. Bluetooth is very similar although it's normally rated for even less range since it is intended to replace wired low speed serial peripherals. They're normally rated for about 100 feet maximum and you can get slightly higher power devices that have a bit more range. I would expect at best 1/3 of the outdoor range if indoors and probably less. It depends so much on what's in the walls. If there's a lot of metal or water, you'll lose a lot of signal. People, tree leaves, etc. all absorb the signal. A lot depends on the type and size of the antenna. If you're really concerned about range, you might have to go with WiFi. Some WiFi links, with a good external antenna, can get ranges of several miles line of sight. They take a lot of power relative to xBee or Bluetooth, but that's the way it needs to be. Any of these (xBee, Bluetooth, or WiFi) will get you a reliable (with error checking and retries) bidirectional link if the range is appropriate for the power, antenna, and interference level.
  • DgswanerDgswaner Posts: 795
    edited 2007-05-16 19:22
    Blue tooth has the same limitations as any RF product. Most USB BT adapters come in 10 meter or 100 meter ranges. The 100m of coarse costs more. you can gain or lose range based on interference. I can wonder around my house with my computer in the basement and make it almost to my 2nd level with the 10 meter (listening to music) the 100 meter works great as far as signal strength.

    I'm a little frustrated with bluetooth. it's a little buggy still. If I use my usb adapter on another computer or switch from my 10m to 100m I basically have to reinstall the whole setup to get it to work. that being said, it was pretty cool to setup a peer to peer network over bluetooth it took all of 2 minutes to configure and have it up and running. Bluetooth looks very promising but I feel it needs a few wrinkles worked out.

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  • Mike GreenMike Green Posts: 23,101
    edited 2007-05-16 20:08
    Sorry, Dgswaner has the Bluetooth ranges right. I think I got confused since I have a mixed 10m/100m range setup at home where a couple of devices have the higher power, but most do not.

    I use a Mac and a Palm with built-in Bluetooth for some things and have never had problems. This is with two Bluetooth keyboards and two Bluetooth mice, two Macs, the Palm, a printer with a Bluetooth adapter, and occasional use of a Bluetooth dialup modem.
  • Aaqil KhanAaqil Khan Posts: 60
    edited 2007-05-22 15:04
    Hi Mike,

    Correct me if I'm wrong, but you mentioned that, "Bluetooth is ... intended to replace wired low speed serial peripherals."

    But, isn't the Bluetooth a replacement for high speed serial peripherals. Zigbee, on the other hand·is used for low speed data rates.



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  • Mike GreenMike Green Posts: 23,101
    edited 2007-05-22 15:23
    Consider that WiFi was intended to provide a wireless replacement for Ethernet, originally with data rates on the order of 1 megaBaud, now 50 megaBaud and higher. The Ethernet was used for multiple high speed (and low speed) communications channels.

    When Bluetooth was proposed, it was to replace multiple conventional low to medium speed serial channels typical of mice, keyboards, modem links, and compressed or moderate fidelity audio. Data rates were expected to be in the 20-50 kiloBaud range or lower, occasionally higher. Range was to be fairly short, typical for the "rat's nest" of wiring associated with a desktop computer, perhaps 10 meters. Later the extended distance / higher power Bluetooth standard was added allowing for up to 30 meters' range.

    ZigBee was an attempt to combine both worlds by using an Ethernet-like protocol with addressible packets, yet using a moderate data rate to keep power consumption low, yet allowing for an intermediate range (between Bluetooth and WiFi) when enough power was available. The data rate is about 250 kiloBaud.

    The WikiPedia has some good articles on the three standards and their histories.

    Post Edited (Mike Green) : 5/22/2007 3:30:22 PM GMT
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