---
title: "Short note: Analog vs digital mux hierarchy"
subject: "Data Communication"
chapter: 6
key: "semester_5/data_communication:analog-vs-digital-mux-hierarchy"
source: https://www.bctengineer.com/q/semester_5/data_communication/analog-vs-digital-mux-hierarchy
site: BCT Engineering
---

# Short note: Analog vs digital mux hierarchy

Data Communication · Chapter 6: Multiplexing and Spreading

- Asked in: 2076 Asoj, 4 marks
- Video: [Analog hierarchy VS Digital hierarchy](https://www.youtube.com/watch?v=eUAJd_yoN1Y) — Current Tutorials
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/analog-vs-digital-mux-hierarchy
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-6

## Question

Write a short note on analog versus digital multiplexing hierarchy.

## Short answer

Analog FDM hierarchy: 12 voice channels form a group (48 kHz), 5 groups a supergroup (240 kHz), 10 supergroups a master group. Digital TDM hierarchy: DS-0 (64 kbps), DS-1/T1 24 channels 1.544 Mbps, up to DS-4 4032 channels. Digital regenerates signal, avoiding noise accumulation.

## Answer

Telephone networks multiplex many 4 kHz voice channels in stages, which form a hierarchy.

#### Analog hierarchy (FDM)
- **Group**: 12 voice channels, 48 kHz, occupying 60–108 kHz.
- **Supergroup**: 5 groups = 60 channels, 240 kHz (312–552 kHz).
- **Master group**: 10 supergroups = 600 channels, about 2.52 MHz.
- **Jumbo group**: 6 master groups = 3600 channels, about 16.98 MHz.

Each level shifts signals by carriers and uses SSB modulation and guard bands.

#### Digital hierarchy (TDM)
Voice is digitised by PCM at 64 kbps (DS0), and then time-multiplexed:
- DS-1 (T1): 24 channels, 1.544 Mbps
- DS-2 (T2): 96 channels, 6.312 Mbps
- DS-3 (T3): 672 channels, 44.736 Mbps
- DS-4 (T4): 4032 channels, 274.176 Mbps

(E-hierarchy: E1 2.048 Mbps, E2 8.448, E3 34.368, E4 139.264 Mbps.)

| Point | Analog | Digital |
|---|---|---|
| Method | FDM | TDM |
| Signal | Analog voice | PCM digital |
| Noise | Accumulates over repeaters | Regenerated, little noise |
| Quality / flexibility | Lower | Higher; can carry data |
| Trend | Obsolete | Standard today |

## Check yourself

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

1. How many voice channels in an analog group?
   A. 5
   B. 12
   C. 60
   D. 600
   Answer: B. A group has 12 channels, 48 kHz. (Key point: Group)

2. DS-1 (T1) has?
   A. 24 channels, 1.544 Mbps
   B. 30 channels, 2.048 Mbps
   C. 96 channels, 6.312 Mbps
   D. 672 channels
   Answer: A. T1 is 24 channels at 1.544 Mbps. (Key point: T1)

3. Why is digital better for noise?
   A. Signals are regenerated at repeaters
   B. Noise accumulates
   C. It uses FDM
   D. Higher power
   Answer: A. Analog noise accumulates over repeaters; digital is regenerated. (Key point: Noise)

4. A master group contains?
   A. 10 supergroups = 600 channels
   B. 5 groups
   C. 6 master groups
   D. 12 channels
   Answer: A. 10 supergroups = 600 channels. (Key point: Master group)

## Related in Data Communication

- [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
- [Multiplexing techniques; analog one explained](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Alist-mux-techniques) — Data Communication, chapter 6
- [Data representation; analog vs digital system](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adata-representation-analog-digital) — Data Communication, chapter 1
- [Digital hierarchy of T-carriers](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3At-carriers-hierarchy) — Data Communication, chapter 6
- [Advantages of digital over analog systems](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adigital-vs-analog-advantages) — Data Communication, chapter 1, asked 5×
- [Compare analog and digital communication](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adigital-vs-analog-comparison) — Data Communication, chapter 1, asked 4×

## 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
- [Analog versus digital measurement system](https://www.bctengineer.com/question.md?key=semester_4%2Finstrumentation_i%3Aanalog-vs-digital-measurement) — Instrumentation I, chapter 1
- [Digital transmission system; analog vs digital](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aanalog-digital-transmission-compare) — Instrumentation II, chapter 5
- [Digital vs analog modulation; GMSK](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Adigital-modulation-gmsk) — Wireless Communication, chapter 4