WiFi is a wireless networking technology based on the IEEE 802.11 family of standards. It uses radio waves to transmit data between devices and a Wireless Access Point (WAP) or router.
| Standard | Max speed | Frequency | Notes |
|---|---|---|---|
| 802.11b | 11 Mbps | 2.4 GHz | Old; long range but slow |
| 802.11g | 54 Mbps | 2.4 GHz | Improved speed; same range issues |
| 802.11n | 600 Mbps | 2.4 / 5 GHz | Dual-band; widely used |
| 802.11ac (WiFi 5) | ~3.5 Gbps | 5 GHz | Fast; shorter range |
| 802.11ax (WiFi 6) | ~9.6 Gbps | 2.4 / 5 / 6 GHz | Current standard; very efficient |
2.4 GHz: longer range, better wall penetration, but more congested (shared with microwaves, Bluetooth). 5 GHz: faster, less congested, but shorter range and weaker through walls.
Wireless networks use CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to manage access to the shared wireless medium (the air).
Unlike wired Ethernet (which uses CSMA/CD — collision detection), wireless networks cannot detect collisions while transmitting (because a device cannot transmit and listen simultaneously). Instead, they avoid collisions:
The RTS/CTS mechanism is particularly important because it solves the hidden node problem: two devices that cannot hear each other but can both hear the WAP — without RTS/CTS, they might transmit simultaneously and collide at the WAP.
Wireless networks are inherently less secure than wired ones — anyone within range can detect the signal. Encryption is essential:
| Protocol | Algorithm | Status |
|---|---|---|
| WEP (Wired Equivalent Privacy) | RC4 stream cipher | 🔴 Broken — do not use. Key can be cracked in minutes. |
| WPA (WiFi Protected Access) | TKIP | 🟡 Deprecated — known vulnerabilities. |
| WPA2 | AES-CCMP | 🟢 Current standard — secure if using AES. |
| WPA3 | AES-GCMP + SAE | 🟢 Newest — uses SAE for stronger handshake; protects against offline dictionary attacks. |
SSID (Service Set Identifier): the name of a WiFi network (e.g. "HomeNetwork"). Hiding the SSID provides minimal security — devices still broadcast probe requests for known networks. Strong passwords and WPA2/WPA3 are essential.
Bluetooth is a short-range wireless technology using the 2.4 GHz ISM band for communication within a PAN (Personal Area Network). Typical range: 10–100 m depending on class.
Bluetooth uses frequency hopping spread spectrum (FHSS) — it rapidly switches between 79 channels 1,600 times per second. This makes it resistant to interference and eavesdropping.
A piconet is a Bluetooth network: one master device and up to 7 active slave devices. Bluetooth is used for: headsets, keyboards, mice, file transfer, smartwatches, IoT sensors.
Bluetooth versions: Bluetooth 5.0+ offers up to 2 Mbps, range up to 400 m (theoretically), low energy (BLE) mode for IoT/sensors.
Uses radio waves to identify and track objects. An RFID tag (attached to an object) communicates with an RFID reader. Tags can be passive (no battery — powered by the reader's radio field) or active (have their own battery). Used in: contactless payments, passport chips, stock tracking, library book systems, access cards.
Very short range (up to 4 cm), derived from RFID. Used for contactless payments (phone or card tapped to terminal), pairing devices, and smart tags. Operates at 13.56 MHz.
Very short range, requires line of sight (no obstacles). Used in TV remote controls, some older file transfer. Now largely replaced by Bluetooth for device communication.
Low-power, low-data-rate wireless protocol designed for IoT (Internet of Things). Used in smart home devices (smart bulbs, thermostats), industrial sensors. Operates on 2.4 GHz. Supports mesh networking — devices can relay signals for each other, extending range.
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