The provided text offers a comprehensive overview of Wi-Fi, covering its technical aspects, standards, applications, and historical context. Here are some key points highlighted in the text:

1. Definition and Standards:

   • Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 standards.
   • IEEE 802.11 standards are widely used for local area networking of devices and internet access.

2. Global Usage:

   • Wi-Fi is the most widely used computer network globally, connecting devices in homes, small offices, and public places like coffee shops, hotels, libraries, and airports.

3. Wi-Fi Alliance and Certification:

   • Wi-Fi is a trademark of the Wi-Fi Alliance, and products must pass interoperability certification testing to be labeled "Wi-Fi Certified."
   • Non-compliant hardware is referred to as WLAN and may or may not work with "Wi-Fi Certified" devices.

4. Industry Involvement:

   • The Wi-Fi Alliance consists of more than 800 companies from around the world (as of 2017).

5. Device Shipments:

   • Over 3.05 billion Wi-Fi-enabled devices are shipped globally each year (as of 2019).

6. Compatibility and Interoperability:

   • Wi-Fi is designed to work seamlessly with its wired sibling, Ethernet.
   • Compatible devices can network through wireless access points with each other and with wired devices and the internet.

7. Frequency Bands and Channels:

   • Wi-Fi commonly uses the 2.4 GHz UHF and 5 GHz SHF radio bands, with multiple channels in each band.
   • Channels can be shared between networks, but only one transmitter can transmit on a channel within range at a time.

8. Radio Band Performance:

   • Wi-Fi's radio bands work best for line-of-sight use.
   • Common obstructions, like walls and home appliances, may reduce range but help minimize interference in crowded environments.

9. Range and Coverage:

   • The range of an access point is approximately 20 m indoors, with some claiming up to a 150 m range outdoors.
   • Hotspot coverage can vary from a single room to many square kilometers with overlapping access points and roaming permitted.

10. Speed and Spectral Efficiency:

    • Over time, the speed and spectral efficiency of Wi-Fi have increased.
    • As of 2019, some Wi-Fi versions, with suitable hardware at close range, can achieve speeds of up to 9.6 Gbit/s.