What is the difference between TDM and FDM?
Multiplexing
Multiplexing is the process of combining several communication signals and converting them into one signal for data transmission.
Types of multiplexing
We can divide multiplexing into analog and digital signal types. We can further divide these into Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM).
The figure below illustrates this:
Time Division Multiplexing (TDM)
Time Division Multiplexing (TDM) transmits and receives digital and analog signals over a shared communication channel by dividing the data frames into different time slots.
Working
The following three processes have the same frequencies, but are divided into different time slots for transmitting signals.
Frequency Division Multiplexing (FDM)
Frequency Division Multiplexing (FDM) transmits and receives combined signals over a shared communication channel in a series of non-overlapping frequencies.
Working
The following three processes have distinct frequency bands for transmitting the signals concurrently.
Difference between TDM and FDM
The difference between TDM and FDM is as follows:
Difference
Attributes | TDM | FDM |
Signals used | Digital and analog signals | Analog signals |
Working principle | Time-sharing | Frequency-sharing |
Requirement | Syncronization pulse | Guard band |
Circuit orientation | Simple | Complex |
Crosstalk | Not prominent | Prominent |
Interference | Low and negligible | High |
Propagation delay | Yes | No |
Efficiency | High | Low |
Cost | Low | High |
Applications | Internet service providers, ISDN, PSTN, and telephone communication | Optical fiber communication, radio and television broadcasting |
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