Which multiplexing technique used to transmit digital signals?

Digital signals can be transmitted using several multiplexing techniques. The choice of technique depends on various factors, including the nature of the transmission medium, the required data rate, and the cost-effectiveness for the application in question. Some of the primary multiplexing methods used for transmitting digital signals include:

1. Time Division Multiplexing (TDM): This technique involves sharing the transmission channel among several signals by allocating a different time slot for the transmission of each signal. It’s like taking turns, where each signal gets a brief period to use the entire channel, one after the other. TDM can be further divided into Synchronous TDM and Asynchronous TDM (also known as Statistical TDM).

2. Frequency Division Multiplexing (FDM): Although FDM is traditionally associated with analog signals, it can also be adapted for digital signals through the allocation of different frequency bands to different signals within the same medium. Each signal modulates a carrier at a unique frequency, allowing multiple signals to be transmitted simultaneously over a single communication channel.

3. Code Division Multiplexing (CDM), also known as Code Division Multiple Access (CDMA): This technique assigns a unique code to each signal to allow multiple signals to be transmitted over the same frequency band simultaneously. CDMA spreads the signals over a wide spectrum, and the receiver uses a matching code to isolate and recover the original signal from among the mix.

4. **Orthogonal Frequency-Division Multip