---
title: "Multiplexing techniques; analog one explained"
subject: "Data Communication"
chapter: 6
key: "semester_5/data_communication:list-mux-techniques"
source: https://www.bctengineer.com/q/semester_5/data_communication/list-mux-techniques
site: BCT Engineering
---

# Multiplexing techniques; analog one explained

Data Communication · Chapter 6: Multiplexing and Spreading

- Asked in: 2069 Asar, 3 marks
- Video: [Types of Multiplexing | FDM TDM WDM | Analog Digital | Computer Networks](https://www.youtube.com/watch?v=WXof7bg_Zys) — Dr. Ankit Verma
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/list-mux-techniques
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-6

## Question

List three main multiplexing techniques and briefly explain any one of the analog multiplexing technique.

## Short answer

The three main multiplexing techniques are Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), and Wavelength Division Multiplexing (WDM). FDM divides the link bandwidth into non-overlapping frequency bands; each signal modulates a different carrier and all are transmitted simultaneously with guard bands to prevent interference. At the receiver, band-pass filters and demodulators separate the signals.

## Answer

#### Three main techniques
1. **Frequency division multiplexing (FDM)**: analog, each signal has its own frequency band.
2. **Time division multiplexing (TDM)**: digital, each signal has its own time slot.
3. **Wavelength division multiplexing (WDM)**: optical, each signal has its own light wavelength.

#### FDM (analog) explained
In FDM the link bandwidth is divided into non-overlapping bands. Each input signal modulates a different carrier (*f1, f2, f3*), moving it to its own band. The modulated signals are added and sent together at the same time. Guard bands prevent overlap. At the receiver, band-pass filters separate the bands and demodulators recover the signals.

```text
 m1 -> [Mod f1] m2 -> [Mod f2]-> [ + ] === link === [BPFs + Demods] -> m1,m2,m3
 m3 -> [Mod f3]/
```

Example: radio and TV broadcast stations; telephone voice channels of 4 kHz each in a group of 12 (60–108 kHz).

## Check yourself

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

1. Which are the three main multiplexing techniques?
   A. ASK, FSK, PSK
   B. FDM, TDM, WDM
   C. PCM, DM, ADM
   D. CSMA, TDMA, CDMA
   Answer: B. FDM, TDM and WDM. (Key point: Three techniques)

2. How does FDM combine signals?
   A. Each signal modulates a different carrier, and the results are added
   B. Signals are sent in turn in time slots
   C. Signals are XOR-ed with chips
   D. Signals are sent on different wavelengths
   Answer: A. Each signal modulates its own carrier f1, f2, f3 and all are added and sent together. (Key point: FDM working)

3. What do receiver band-pass filters and guard bands do in FDM?
   A. Increase data rate
   B. Create time slots
   C. Separate the bands and prevent overlap
   D. Generate carriers
   Answer: C. BPFs separate bands, while guard bands prevent overlap. (Key point: Receiver and guard bands)

## Related in Data Communication

- [Time division multiplexing explained](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Atdm-explain) — Data Communication, chapter 6, asked 3×
- [Frequency division multiplexing explained](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Afdm-explain) — Data Communication, chapter 6, asked 3×
- [Short note: Analog vs digital mux hierarchy](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aanalog-vs-digital-mux-hierarchy) — Data Communication, chapter 6
- [Digital vs analog spread spectrum](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aspread-spectrum-digital-vs-analog) — Data Communication, chapter 6

## Related in other subjects

- [Analog vs digital multiplexing; 24-channel system](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aanalog-digital-mux-24-channel) — Telecommunications, chapter 3
- [Multiplexing techniques and TDM standards](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Amultiplexing-techniques-tdm-standards) — Telecommunications, chapter 3
- [Digital carrier system and multiplexing techniques](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Adigital-carrier-multiplexing) — Telecommunications, chapter 3
- [Compare multiplexing techniques](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Acompare-multiplexing-techniques) — Telecommunications, chapter 3