- 2076 Bhadra · 5 marks
Short note: WiFi
Short answer
Wi-Fi is IEEE 802.11 WLAN technology in unlicensed ISM bands. Versions range from 802.11b at 11 Mbps to 802.11ax at about 9.6 Gbps, using OFDM, MIMO and OFDMA. MAC uses CSMA/CA with RTS/CTS and ACKs; security is WPA2/WPA3.
Write a short note on WiFi.
Wi-Fi is the trade name (Wi-Fi Alliance) for wireless local area networks based on the IEEE 802.11 standards. It connects laptops, phones and other devices to each other and to the Internet over short range (about 30–100 m) using unlicensed ISM bands.
Versions
| Standard | Year | Band | Max rate | PHY |
|---|---|---|---|---|
| 802.11b | 1999 | 2.4 GHz | 11 Mbps | DSSS/CCK |
| 802.11a | 1999 | 5 GHz | 54 Mbps | OFDM |
| 802.11g | 2003 | 2.4 GHz | 54 Mbps | OFDM |
| 802.11n (Wi-Fi 4) | 2009 | 2.4/5 GHz | 600 Mbps | OFDM + MIMO |
| 802.11ac (Wi-Fi 5) | 2013 | 5 GHz | ~6.9 Gbps | MU-MIMO, 256-QAM |
| 802.11ax (Wi-Fi 6) | 2019 | 2.4/5/6 GHz | ~9.6 Gbps | OFDMA |
Architecture
[STA]~~\
[STA]~~~[Access Point]---Ethernet---Internet
[STA]~~/ (BSS)
Ad hoc: [STA]~~~[STA] (IBSS, no AP)
- Infrastructure mode: stations connect through an access point (AP); several APs linked by a distribution system form an ESS.
- Ad hoc mode: stations talk directly.
MAC: CSMA/CA (carrier sense multiple access with collision avoidance) with optional RTS/CTS to solve the hidden-terminal problem; acknowledgements for each frame.
Security: WEP (weak, obsolete) → WPA → WPA2 (AES-CCMP) → WPA3.
Advantages: no cabling, mobility, cheap, high data rates. Limitations: short range, interference in the crowded 2.4 GHz band, shared capacity, security concerns.
Applications: home and office networks, public hotspots, campus networks, offloading mobile data, IoT devices.
✓ Answer checked by Claude Opus 5.5 (high effort)