CyberCertPrepNetwork FundamentalsWireless BasicsEASYFree question
What RF interference source operates in the same 2.4 GHz ISM band as Wi-Fi and is commonly found in consumer IoT deployments near wireless access points?
- A.ZigBee IoT devices exclusively use 915 MHz and do not interfere with 2.4 GHz Wi-Fi
- B.Baby monitors using the 5.8 GHz DECT standard interfere with 5 GHz Wi-Fi channels only
- C.Bluetooth devices (phones, speakers, headsets) use the 2.4 GHz ISM band (2.402-2.480 GHz) with frequency hopping spread spectrum (FHSS); while Bluetooth uses adaptive hopping that avoids occupied Wi-Fi channels, high density of Bluetooth devices can still degrade 2.4 GHz Wi-Fi performance
- D.Smart lighting systems using Z-Wave operate at 2.4 GHz and are the primary interference source in IoT environments
Why C is correct
Bluetooth (IEEE 802.15.1) uses the 2.4 GHz ISM band with 79 channels at 1 MHz spacing, using FHSS to hop 1600 times per second. Bluetooth 2.0+ uses AFH (Adaptive Frequency Hopping) to detect and avoid active Wi-Fi channels. However, very high Bluetooth density can still impact 2.4 GHz Wi-Fi. Other 2.4 GHz ISM band users: ZigBee (2.4 GHz, 16 channels), analog baby monitors (non-DECT), microwave ovens, and wireless video cameras. Z-Wave uses 908.42 MHz (US) not 2.4 GHz.
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