Multiplexing (FDM, TDM, CDM)
Multiplexing is a technique used in telecommunications and signal transmission to combine multiple signals over a single communication channel. Frequency Division Multiplexing (FDM) assigns each signal a unique frequency band, Time Division Multiplexing (TDM) allocates distinct time slots to each signal, and Code Division Multiplexing (CDM) uses unique codes for each channel. These methods enhance channel efficiency, allowing simultaneous transmission of multiple data streams in telecom, signals, and power systems.
Multiplexing (FDM, TDM, CDM)
Multiplexing is a technique used in telecommunications and signal transmission to combine multiple signals over a single communication channel. Frequency Division Multiplexing (FDM) assigns each signal a unique frequency band, Time Division Multiplexing (TDM) allocates distinct time slots to each signal, and Code Division Multiplexing (CDM) uses unique codes for each channel. These methods enhance channel efficiency, allowing simultaneous transmission of multiple data streams in telecom, signals, and power systems.
💡 Key Takeaways
- Explain how FDM, TDM, and CDM allocate resources (frequency bands, time slots, and codes) to carry multiple signals in one channel.
- Identify typical use cases for each method, such as FDM in analog channels, TDM in digital telephony, and CDM in code-based wireless systems.
- Evaluate the trade-offs of each technique, including spectral efficiency, complexity, latency, and synchronization requirements.
- Describe how demultiplexing separates signals at the receiver and why guard bands or code orthogonality are essential to minimize interference.
❓ Frequently Asked Questions
What is multiplexing?
Multiplexing is a technique to combine several signals into one shared transmission medium, allowing efficient use of bandwidth by separating them at the destination.
What is FDM (Frequency-Division Multiplexing) and how does it work?
FDM divides the available bandwidth into separate frequency bands; each signal modulates its own band, so all signals travel simultaneously without interference.
What is TDM (Time-Division Multiplexing) and how does it work?
TDM assigns distinct time slots to different signals on a shared channel; each signal transmits in its slot, one after another.
What is CDM/CDMA (Code Division Multiplexing) and how does it work?
CDM uses unique codes to spread each signal across the same frequency band; receivers use the corresponding code to extract their signal, enabling multiple signals to share the channel.
When should you use FDM, TDM, or CDM?
Use FDM for analog, continuous streams with sufficient bandwidth; use TDM for digital, time-sliced transmission with synchronization; use CDM when sharing the same spectrum with spread-spectrum benefits, noting higher processing and code management requirements.