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Short note: Analog vs digital mux 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.

Write a short note on analog versus digital multiplexing hierarchy.

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.)

PointAnalogDigital
MethodFDMTDM
SignalAnalog voicePCM digital
NoiseAccumulates over repeatersRegenerated, little noise
Quality / flexibilityLowerHigher; can carry data
TrendObsoleteStandard today

✓ Answer checked by Claude Sonnet 5.5

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