The IEEE 802.15.4 standard, upon which ZigBee is based, specifies the 2.4 GHz Industrial, Scientific, and Medical (ISM) band for worldwide operation. This band is also heavily utilized by IEEE 802.11 (Wi-Fi) networks, leading to significant potential for co-channel and adjacent-channel interference. The most effective method to mitigate this interference is to ensure the two technologies operate in completely separate, non-overlapping frequency bands. By moving all 802.11 communications to the 5 GHz band, the ZigBee network can operate in the 2.4 GHz band without contention from Wi-Fi signals, thus providing the most comprehensive interference minimization.

A. ZigBee is not defined by the IEEE 802.15.4 standard to operate in the 6 GHz band.

C. ZigBee is not defined by the IEEE 802.15.4 standard to operate in the 5 GHz band.

D. This action would force both networks to compete for the same 2.4 GHz spectrum, maximizing interference rather than minimizing it.

1. IEEE Std 802.15.4™-2020, IEEE Standard for Low-Rate Wireless Networks. Clause 10, "2450 MHz PHY," specifies the physical layer parameters for operation in the 2400–2483.5 MHz band, which is the worldwide band for ZigBee.

2. IEEE Std 802.11™-2020, IEEE Standard for Information Technology...Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Annex E, "Channel numbering across regulatory domains," details the channelization for 802.11 operation in both the 2.4 GHz and 5 GHz bands.

3. Sikora, A., & Groza, V. F. (2005). Coexistence of IEEE 802.15.4 with other systems in the 2.4 GHz-ISM-Band. IEEE Instrumentation and Measurement Technology Conference Proceedings. Section IV, "Coexistence Improvement," discusses frequency separation as a primary mitigation strategy, stating, "The most obvious but also most effective method is to use different frequency bands for the different systems (e.g. IEEE 802.11a in the 5 GHz band)." DOI: 10.1109/IMTC.2005.1604455