RF4CE radios share the 2.4-GHz frequency band with WiFi, Bluetooth, and ZigBee communications, which might cause interference and lost packets. But the manufacturers of wireless chips have figured out how to avoid that possibility. The IEEE 802.15.4 radio technology answers many potential problems before engineers even get to a protocol stack or their application code. "The radios use a a protocol based on CSMA/CA, or carrier-sense multiple-access with collision avoidance," said Tim Dry of Renesas. "So a radio avoids interfering with other transmissions from the start. Suppose a radio transmits on a given frequency and another radio wants to use the same frequency. The waiting radio will detect this transmission and continues to wait for a random period before it tries again. Most RF4CE applications can tolerate a slight delay, so your TV might take a second or two longer to turn on if you have a lot of other wireless signals in the 2.4-GHz band simultaneously."The RF4CE stack is designed to use channels 15, 20 and 25 which are not used by 802.11b/g thereby avoiding interference with WiFi.
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