---
title: "Short note: Means of bandwidth utilization"
subject: "Data Communication"
chapter: 6
key: "semester_5/data_communication:bandwidth-utilization-means"
source: https://www.bctengineer.com/q/semester_5/data_communication/bandwidth-utilization-means
site: BCT Engineering
---

# Short note: Means of bandwidth utilization

Data Communication · Chapter 6: Multiplexing and Spreading

- Asked in: 2074 Chaitra, 5 marks
- Video: [Bandwidth Utilization and Multiplexing](https://www.youtube.com/watch?v=tIFofKWSN2c) — FARAH DIYANA BT. ABDUL RAHMAN
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/bandwidth-utilization-means
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-6

## Question

Write a short note on means of bandwidth utilization.

## Short answer

Bandwidth utilization is achieved by multiplexing (FDM, TDM, WDM) to efficiently share a link when its capacity exceeds signal bandwidth, and by spread-spectrum techniques (FHSS, DSSS) that deliberately widen bandwidth for security and jamming resistance. Multiplexing aims for efficiency; spreading aims for protection.

## Answer

**Bandwidth utilization** means making the best use of the available bandwidth of a link, which can be done in two ways: **multiplexing** and **spreading**.

#### Multiplexing
Several signals share one link efficiently when the link bandwidth is larger than each signal needs.
- **FDM**: each signal gets its own frequency band (analog; radio, TV).
- **TDM**: each signal gets its own time slot (digital; telephone). May be synchronous or statistical.
- **WDM**: different light wavelengths carry different signals in an optical fibre (a form of FDM for light). DWDM packs many wavelengths.

```text
 FDM: bands side by side  | f1 | f2 | f3 |
 TDM: slots in turn       |A|B|C|A|B|C|
```

#### Spreading (spread spectrum)
The bandwidth of a signal is widened for **security and anti-jamming**, not for efficiency.
- **FHSS**: carrier hops among frequencies in a PN pattern.
- **DSSS**: each bit is replaced by many chips, so the signal occupies a larger band.

#### Comparison of purpose
- Multiplexing: efficiency, link bandwidth > signal bandwidth.
- Spreading: protection against eavesdropping and jamming, signal bandwidth is deliberately increased.

CDMA uses spreading for sharing the same band.

## Check yourself

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

1. What are the two means of bandwidth utilization?
   A. Modulation and demodulation
   B. Multiplexing and spreading
   C. Sampling and quantisation
   D. Coding and decoding
   Answer: B. Bandwidth is utilised by multiplexing and by spreading. (Key point: Two ways)

2. What is the purpose of multiplexing?
   A. Increase security against jamming
   B. Efficient sharing of a link when link bandwidth exceeds each signal's need
   C. Deliberately widen each signal's bandwidth
   D. Reduce signal power
   Answer: B. Multiplexing targets efficiency: several signals share one link of larger bandwidth. (Key point: Purpose of multiplexing)

3. Why is the bandwidth of a signal deliberately widened in spreading?
   A. To carry more users at higher efficiency
   B. To lower the cost of the link
   C. For security and anti-jamming, not efficiency
   D. To remove the need for a carrier
   Answer: C. Spreading increases signal bandwidth for protection against eavesdropping and jamming. (Key point: Purpose of spreading)

4. What does WDM do?
   A. Gives each signal a time slot on copper
   B. Spreads bits with chips
   C. Hops carrier frequencies
   D. Carries different signals on different light wavelengths in a fibre
   Answer: D. WDM is FDM for light: each signal gets its own wavelength. (Key point: WDM)

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