Greetings Mr. Enno:
As the name suggests, adjacent channel power is the amount of power a transmitter allows to "bleed" into the channel just above and below it. Lower ACPs are always better, because it means you are not as likely to interfere with a co-existing system trying to operate in the same frequency space.
Here is an illustration that uses co-existence of Zigbee with WiFi. Bluetooth could also be added to the picture because like ZigBee, it uses a frequency-hopping spread spectrum scheme.http://www.xbow.com/Products/Product_pd ... erence.pdf
- Kirt Blattenberger