The 2.4 GHz band is an RF range from approximately 2.4 to 2.495 GHz used by wireless LANs. Its lower frequency penetrates obstacles better than 5 GHz and 6 GHz, but shared use by Bluetooth, microwave ovens, cordless telephones, and other technologies can create congestion and interference. section 18.2.2
The band contains 14 channels, normally 20 MHz wide. Transmitting and receiving devices must use the same channel, and overlapping channels make careful channel selection essential for neighboring access points. section 18.2.2 section 18.5
Use these exam-relevant channel-planning facts:
- Prefer non-overlapping channel patterns 1-6-11 or 1-5-9-13 for adjacent access points. section 18.2.3
- Check local regulations because not every channel is available in every country. section 18.2.2 section 18.5
- Associate 802.11b and 802.11g with 2.4 GHz; 802.11a and 802.11ac use 5 GHz. section 18.2.3
Exam scenario
When asked which standards require careful channel selection because of overlapping 2.4 GHz channels, select 802.11b and 802.11g. section 18.2.3
Figure 18.9 Channels in the 2.4 GHz band. There are 14 channels in total. Because many channels in the 2.4 GHz band overlap, channels 1, 6, and 11 should be used to avoid interference.
Use the channel-layout figure to visualize overlap and the recommended 1, 6, and 11 plan. section 18.2.2
