---
title: "Short note: WiMAX"
subject: "Wireless Communication"
chapter: 8
key: "semester_7/wireless_communication:wimax-short-note"
source: https://www.bctengineer.com/q/semester_7/wireless_communication/wimax-short-note
site: BCT Engineering
---

# Short note: WiMAX

Wireless Communication · Chapter 8: Wireless Systems and Standards

- Asked in: 2078 Chaitra, 4 marks; 2073 Magh, 5 marks; 2072 Asoj, 3 marks (asked 3 times)
- Video: [Wireless Technology | WiMAX (IEEE 802.16a)](https://www.youtube.com/watch?v=ysgm55eG3EI) — RANJI RAJ
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/wireless_communication/wimax-short-note
- Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-8

## Question

Write a short note on WiMAX.

## Short answer

WiMAX, based on IEEE 802.16, provides broadband wireless access for metropolitan areas. It employs OFDM/OFDMA, adaptive modulation (BPSK to 64-QAM), MIMO, and operates in 2–11 GHz bands with ranges up to 50 km. Standards include fixed (802.16d) and mobile (802.16e) versions with QoS classes, PKM security, and both TDD and FDD duplexing.

## Answer

**WiMAX (Worldwide Interoperability for Microwave Access)** is a broadband wireless access technology based on the **IEEE 802.16** standard. It provides high-speed data over metropolitan areas (WMAN) as a wireless alternative to cable and DSL, for "last mile" access.

**Key features**
- **Standards**: 802.16d (2004) for fixed access; 802.16e (2005) "Mobile WiMAX" with handoff; 802.16m (WiMAX 2) aimed at 4G.
- **Physical layer**: OFDM (fixed) and **OFDMA** (mobile, scalable FFT 128–2048); adaptive modulation and coding (BPSK, QPSK, 16-QAM, 64-QAM).
- **Spectrum**: 2–11 GHz for non-line-of-sight; 10–66 GHz for line-of-sight. Common bands 2.3, 2.5, 3.5 GHz; channel widths 1.25–20 MHz.
- **Range and rate**: up to about 50 km (fixed, LOS) and typically 5–10 km NLOS; data rates up to ~70 Mbps shared (802.16e), ~1 Gbps target in 802.16m.
- **Duplexing**: TDD and FDD.
- **MIMO and smart antennas** for capacity and coverage.
- **QoS classes**: UGS, rtPS, nrtPS, ertPS and best effort; connection-oriented MAC with scheduling by the base station.
- **Security**: PKM authentication, AES encryption.

```text
 Internet--[WiMAX BS]~~~~~~~~[CPE]--home LAN
               ~~~~~~~~~~[laptop/mobile]
               ~~~~[relay]~~~[remote user]
```

**Applications**: broadband in rural areas, backhaul for Wi-Fi hotspots and cell sites, mobile broadband. WiMAX lost the 4G market to LTE, but is still used for fixed wireless access in some places.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. WiMAX is based on which IEEE standard?
   A. IEEE 802.11
   B. IEEE 802.15
   C. IEEE 802.16
   D. IEEE 802.3
   Answer: C. WiMAX is the broadband wireless access technology built on IEEE 802.16 (802.11 is Wi-Fi). (Key point: Standard)

2. Which physical layer technique does Mobile WiMAX (802.16e) use, with scalable FFT size 128-2048?
   A. DSSS
   B. OFDMA
   C. FHSS only
   D. GMSK
   Answer: B. Mobile WiMAX uses scalable OFDMA; fixed WiMAX uses OFDM. (Key point: Mobile WiMAX PHY)

3. Which band is used for non-line-of-sight WiMAX operation?
   A. 10-66 GHz
   B. Below 1 GHz only
   C. 60 GHz only
   D. 2-11 GHz
   Answer: D. 2-11 GHz supports NLOS; 10-66 GHz is for line-of-sight links. (Key point: Spectrum and LOS)

4. Which set lists WiMAX MAC QoS service classes?
   A. UGS, rtPS, nrtPS, ertPS, best effort
   B. TCH, SDCCH, FACCH, PCH
   C. AF, EF, DF, CS
   D. CBR, VBR, ABR, UBR only
   Answer: A. WiMAX defines UGS, rtPS, nrtPS, ertPS and best effort, scheduled by the base station. (Key point: QoS classes)