Fundamentals of computer networks: Wi-Fi

The idea

Wi-Fi is the family of wireless local area network technologies that lets a device join a network without a physical cable. A wireless access point, usually connected to a wired network, broadcasts a radio signal over a small area such as a home, school or café. A device with a wireless network interface card detects the network, authenticates (often with a password such as WPA2), and then exchanges data using radio waves on agreed frequency bands. Because the medium is shared, nearby devices contend for airtime, and signal strength falls with distance and with obstructions such as walls. Security matters: an open network lets others join, so encryption and a strong passphrase protect traffic. Wi-Fi is convenient and cheap to install but can suffer interference and has a shorter range than wired Ethernet.

What earns the marks

• Wi-Fi is a wireless technology used to connect devices to a local area network without cables.
• A wireless access point broadcasts the signal, and devices use a wireless network interface card to connect.
• Wi-Fi uses radio waves and typically has a limited range, affected by distance and obstructions.
• Security is provided by authentication and encryption, for example a password and WPA2.
• Wi-Fi is convenient but can suffer interference and is generally slower or less reliable than a wired connection.

Common mistakes and how to put them right

• Confusing Wi-Fi with mobile/cellular data.

  Put it right by naming the access point and local range.

• Thinking Wi-Fi needs no security.

  Put it right by stating that encryption and a passphrase protect it.

• Assuming Wi-Fi has unlimited range.

  Put it right by describing the limited local coverage.

Exam tips

• Read the option carefully and match it to the defining feature: wireless, local area, radio waves, access point.
• Eliminate options that describe wired Ethernet or cellular data, which are different technologies.
• Link Wi-Fi to its practical trade-offs (convenience versus interference and range) to justify your choice.