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Actually, no, it isn't logical at all . . . if the channel is busy, transmitting anyhow will be useless. |
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Not necessarily. What you (and many others) forget is that the noise levels seen by the receiver and those seen by the transmitter may be significantly different (perhaps because of another transmitter on the flight-line, a blue-tooth mobile or whatever).
Although the transmitter may see a very high noise level on its chosen channel, the receiver may not see the same noise. So, if the transmitter sends a packet, the receiver may still get it, even though the noise level at the transmitter end is very high.
HOWEVER -- since the Zigbee/XBee networking protocol relies on CSMA to avoid collisions, JD's claims of 120 concurrent users may be less than accurate since he has disabled this critical feature.
Without CSMA the chances of packet collisions between mutliple XPS systems increases significantly and may become an issue if you've got more than 2-3 users per operating channel. Not an issue at most fields -- but something to consider if you are under the illusion that 120 XPS systems can operate concurrently without problems.
It's also worth nothing that regardless of the CSMA setting on the XBeePro modules, there is never any CSMA for the ACK packets.