The electromagnetic spectrum is the complete range of electromagnetic radiation. Radio frequency (RF) occupies approximately 20 kHz to 300 GHz, and wireless LANs use the 2.4 GHz, 5 GHz, and 6 GHz bands. Choosing among these bands requires balancing speed, interference, obstacle penetration, and coverage. section 18.5 section 18.2.1
Use frequency and channel behavior to assess wireless LAN options:
- Measure frequency in hertz, or oscillations per second: kHz equals 1,000 Hz, MHz equals 1,000,000 Hz, GHz equals 1,000,000,000 Hz, and THz equals 1,000,000,000,000 Hz. section 18.2.1 section 18.5
- Expect higher frequencies to support higher data rates and encounter less wireless crowding, but experience greater absorption by obstacles. section 18.2.1
- Expect lower frequencies to penetrate obstacles more effectively and cover larger distances, but provide lower typical rates and more crowding. section 18.2.1
- Treat 2.4 GHz as an overlapping-channel band, 5 GHz as a mostly non-overlapping 20 MHz channel band, and 6 GHz as the newest band with more non-overlapping channels. section 18.5
Channel planning example
For adjacent access points using 2.4 GHz, select non-overlapping channel plans such as 1–6–11 or 1–5–9–13. In 5 GHz, standard 20 MHz channels do not overlap; combining channels into 40, 80, or 160 MHz widths can increase rates but leaves fewer channels. section 18.5
Period is the time required for one complete oscillation. A 4 Hz wave completes four oscillations per second, so each oscillation has a 0.25-second period. section 18.2.1 section 18.5
