Wi-Fi Impact on 802.15.4 Radios#

Globally, Wi-Fi operates in the 2.4 GHz ISM band and uses up to 14 overlapping channels, each with a bandwidth of 20 MHz or 22 MHz. It supports transmit power levels up to +30 dBm. In contrast, IEEE 802.15.4 defines 16 non-overlapping channels with 2 MHz bandwidth and 5 MHz spacing, and supports transmit power levels up to +20 dBm. The channel mappings for Wi-Fi and IEEE 802.15.4 are illustrated in the following figure.

Wi-Fi channel availability depends on regional regulations. In the United States, only channels 1 through 11 are permitted. Zigbee supports channels 11 through 26, although channels 25 and 26 must operate at reduced transmit power to comply with FCC regulations.