- 2081 Baisakh · 4 marks
TDMA versus FDMA
Compare and contrast between TDMA and FDMA.
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.
✓ Answer checked by Claude Opus 5.5 (high effort)
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