Hertz (Hz, MHz, GHz) in Wireless Communications

In wireless communications, the abbreviation Hz — which stands for hertz, after the 19th-century scientist Heinrich Hertz — refers to the transmission frequency of radio signals in cycles per second:

• 1 Hz equals one cycle per second.
• 1 MHz (megahertz) equals 1 million cycles per second (or 1 million Hz).
• 1 GHz (gigahertz) equals 1 billion cycles per second (or 1000 MHz).

Wireless computer networks operate at different transmission frequencies, depending on the technology they use. Wireless networks also operate over a range of frequencies (called bands) rather than one exact frequency.

A network that uses higher-frequency wireless radio communication does not necessarily offer faster speeds than lower-frequency wireless networks.

Hz in Wi-Fi Networking

Wi-Fi networks operate in either 2.4 GHz or 5 GHz bands. These are ranges of radio frequency open for public communication (i.e., unregulated) in most countries.

The 2.4 GHz Wi-Fi bands range from 2.412 GHz on the low end to 2.472 GHz on the high end (with one additional band enjoying limited support in Japan). Starting with 802.11b and up to the latest 802.11ac, 2.4 GHz Wi-Fi networks all share these same signal bands and are compatible with each other.

Wi-Fi began using 5 GHz radios starting with 802.11a, although their mainstream use in homes started only with 802.11n. The 5 GHz Wi-Fi bands range from 5.170 to 5.825 GHz, with some additional lower bands supported in Japan only.

Other Types of Wireless Signaling Measured in Hz

Beyond Wi-Fi, consider these other examples of wireless communications:

• Cordless phones operate in a 900 MHz range, as does the newer 802.11ah standard
• Bluetooth network connections use 2.4 GHz signaling, similar to Wi-FI, but Bluetooth and Wi-Fi are incompatible.
• Several 60 GHz wireless network protocols have been developed for special applications that involve very large amounts of data traveling over very short distances.

Why so many different variations? For one, different types of communications must use separate frequencies to avoid colliding with each other. In addition, higher-frequency signals such as 5 GHz can carry larger amounts of data (but, in return, have greater restrictions on distance and require more power to penetrate obstructions).