The IEEE 802.15.4 protocol operates in the unlicensed spectrum in three different radio frequency bands: 868 MHz, 915 MHz, and 2400 MHz. The intent is to have as wide a geographical footprint as possible, which implies three different bands and multiple modulation techniques. While the lower frequencies allow 802.15 to have fewer issues with RF interference or range, the 2.4 GHz band is by far the most often used 802.15.4 band worldwide. The higher frequency band has gained its popularity because the higher speed allows for shorter duty cycles on transmitting and receiving, thus conserving power.
The other factor that has made the 2.4 GHz band popular is its acceptance in the market due to the popularity of Bluetooth. ...
