The spectrum is the complete set of frequencies available to create a link, and a channel or band is a small set of frequencies within the spectrum. Figure 8-7 shows a breakdown of the radio frequency spectrum.

Figure 8-7 Radio Frequency Spectrum

Each range of frequencies in the spectrum is used for several different classes of applications, from navigation to satellite communications. Within each band, smaller sets of frequencies are set aside for specific applications.

Wi-Fi
Wi-Fi—alternately WiFi or Wireless LAN—is ubiquitous in homes, businesses, and offices. This technology is (most likely) the most widely used technology for connecting to a network in the world.

Note
Chapter 11, “Basic Network Hardware,” considers Wi-Fi configuration in a home network.

Wi-Fi Etymology

Wi-Fi is a marketing takeoff on Hi-Fi, which stands for High Fidelity. Radio systems sporting the Hi-Fi designation reproduce a wider range of the audio spectrum, allowing them to produce more accurate renditions of music regardless of the source. Wi-Fi evokes a highly reliable wireless system.

Wi-Fi is a group of standards ratified and supported by the Institute of Electrical and Electronics Engineers (IEEE) within the 802.11 working group. A letter is added after 802.11 to differentiate between the standards, as shown in Table 8-2.

Table 8-2 802.11 Wi-Fi Standards

There are specific channels within the frequencies given within each country. Table 8-3 shows the channels and their corresponding frequencies used by the 802.11b, g, n, and ax standards in the 2.4 GHz range.

Table 8-3 2.4 GHz Channels and Frequencies for 802.11 Wi-Fi

Table 8-4 shows some channels and their corresponding frequencies for the 802.11a, h, j, n, ac, and ax standards in the 5 GHz range. Some countries require Transmitter Power Control (TPC) to operate devices on these frequencies.

Table 8-4 5 GHz Channels and Frequencies for 802.11 Wi-Fi

Because regulations vary widely, different versions of Wi-Fi devices may be sold in each country. The study guide is at
https://www.acedexam.com/500-425-caaa-cisco-appdynamics-associate-administrator/

Table 8-3 and Table 8-4 note some frequencies can be used only if TPC is used. TPC is a method for Wi-Fi transmitters to detect other transmitters in the area and the strength of their connection, and reduce their transmission power to the minimum power necessary to operate correctly.