---
title: "TDMA versus FDMA"
subject: "Wireless Communication"
chapter: 7
key: "semester_7/wireless_communication:tdma-vs-fdma"
source: https://www.bctengineer.com/q/semester_7/wireless_communication/tdma-vs-fdma
site: BCT Engineering
---

# TDMA versus FDMA

Wireless Communication · Chapter 7: Multiple Access in Wireless Communication

- Asked in: 2081 Baisakh, 4 marks
- Video: [Multiple Access #3. Time (TDMA), Freq (FDMA), Code (CDMA), Orthogonal (OFDMA), Spatial (SDMA)](https://www.youtube.com/watch?v=-Nux72R5W24) — Technologies Discussion
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/wireless_communication/tdma-vs-fdma
- Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-7

## Question

Compare and contrast between TDMA and FDMA.

## Answer

**FDMA** gives each user a separate frequency channel for the whole call, while **TDMA** gives each user the whole carrier (shared with others) for a separate, repeating **time slot**.

| Point | FDMA | TDMA |
|---|---|---|
| Resource shared | Frequency bands | Time slots on a carrier |
| Transmission | Continuous | Burst (discontinuous) |
| Users per carrier | One | Several (e.g. 8 in GSM) |
| Bandwidth per channel | Narrow (e.g. 30 kHz AMPS) | Wider (e.g. 200 kHz GSM) |
| ISI / equalization | Little ISI, no equalizer needed | High rate, needs adaptive equalizer |
| Synchronisation | Not critical | Strict time sync and guard times |
| Duplexer | Needed (FDD) | Not needed if TDD/offset slots |
| Overhead | Guard bands | Guard times, sync and training bits |
| Handoff | Hard, needs interruption | Simpler (MAHO in idle slots) |
| Hardware at BS | One transceiver per channel | One transceiver serves several users |
| Example | AMPS, NMT | GSM, IS-136 |

**Similarities:** both are narrowband, orthogonal (non-interfering in the ideal case) and channel-based, and they are usually combined (GSM is FDMA/TDMA).

**Further TDMA advantages:** TDMA allows a variable data rate by giving a user more slots, and it saves battery because the transmitter is off between bursts.

## Check yourself

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

1. What does each scheme give a user?
   A. FDMA a separate frequency channel; TDMA a repeating time slot on a shared carrier
   B. FDMA a time slot; TDMA a frequency
   C. Both a code
   D. Both the whole band
   Answer: A. FDMA divides frequency, TDMA divides time on a carrier. (Key point: Basic difference)

2. Which needs an adaptive equalizer?
   A. TDMA, because of high rate and ISI
   B. FDMA, because of narrow band
   C. Neither
   D. Both equally
   Answer: A. TDMA's higher channel rate causes ISI; FDMA narrowband channels have little ISI. (Key point: Equalization)

3. Which statement is correct?
   A. FDMA needs strict time sync and guard times
   B. TDMA needs strict time sync and guard times; FDMA does not
   C. Neither needs sync
   D. Both need only guard bands
   Answer: B. TDMA overhead includes guard times, sync and training bits; FDMA overhead is guard bands. (Key point: Synchronisation)

4. What is an advantage of TDMA?
   A. Transmitter is off between bursts, saving battery, and one BS transceiver serves several users
   B. Continuous transmission
   C. One transceiver per user at BS
   D. Needs a duplexer always
   Answer: A. Burst transmission saves power and shares hardware among slots. (Key point: Battery and hardware)

## Related in Wireless Communication

- [FDMA vs TDMA; operation of FHMA](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Afdma-tdma-fhma) — Wireless Communication, chapter 7
- [Advantages and disadvantages of FDMA, TDMA, CDMA](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Afdma-tdma-cdma-pros-cons) — Wireless Communication, chapter 7
- [Advantages of TDMA over FDMA](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Atdma-advantages-over-fdma) — Wireless Communication, chapter 7
- [Spread spectrum multiple access; FDMA vs CDMA](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Aspread-spectrum-ma-fdma-cdma) — Wireless Communication, chapter 7
- [Multiple access; FDMA vs CDMA](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Amultiple-access-fdma-vs-cdma) — Wireless Communication, chapter 7

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