Hi, Ray - Would you accept input from a non-expert?
'I wonder if any of our wireless experts would care to chime in on the issue of BER in the ISM bands'
The 2.4 GHz ISM band is going to get pretty busy. It's scary. I recently used some wireless handsets from MOT that work at 2.4 GHz. Bluetooth will work at 2.4 GHz, as will 802.11a and 802.11b. We traded some thoughts about this on the WIN thread, and I am convinced that Bluetooth, with its frequency-hopping technology, offers the strong possibility of packet header collisions, and therefore, re-transmissions, when 802.11 is in use.
I am not familiar with all 802.11 implementations, but in general, the detection of a clear channel for transmission is likely to be defeated by a frequency-hopping technology that does not, itself utilize collision detection/avoidance mechanisms.
Moreover, I note with alarm that there are extensions to the Bluetooth spec that allow for increased transmit power and range, in some circumstances.
Carrier Sense Multiple Access/Collision Detection (CSMA/CD) is a means of avoiding collisions on a LAN, but my uneducated interpretation is that this mechanism is meant to defeat relatively steady-state phenomena.
In the 5 GHz band, I do not expect the problem to be as bad, however the potential difficulties you refer to apply to all standards, IEEE 802.11a and b, and HiperLAN1 and 2.
Yeah. No doubt about it. Could be trouble.
Best regards,
Jim |
