Question

The TDM, FDM, and CDM are different multiplexing techniques used by the physical layer. • Mention the pros (at least one with explanation) and the cons (at least one with explanation) of each of these techniques.

Answer 1

1. TDM - Time division multiplexing

       Pros:

• Time division multiplexing systems are more flexible than frequency division multiplexing.
• Time division multiplexing circuitry is not complex.
• Problem of cross talk is not severe.
• Full available channel bandwidth can be utilized for each channel.

      Cons:

• Synchronization is required in time division multiplexing.
• Complex to implement.
• Due to slow narrowband fading, all the TDM channels may get wiped out.

      2. FDM :

      Pros:

• The frequency division multiplexing does not need synchronization between its transmitter and receiver for proper operation.
• A large number of signals (channels) can be transmitted simultaneously.
• Due to slow narrow band fading only a single channel gets affected.
• The Demodulation process of frequency division multiplexing is easy.

      Cons:   

• All the frequency division multiplexing channels get affected due to wideband fading.
• A large number of modulators and filters are required.
• The communication channel must have a very large bandwidth.
• The frequency division multiplexing suffers from the problem of crosstalk. v lntermodulation distortion takes place

      3.CDM : Code-division multiplexing

    Pros:

• The CDM does not require any synchronization.
• It has more number of users can share the same bandwidth.
• It is well-matched with other cellular technologies.
• Due to codeword allocated to each user, interference is reduced.
• Efficient practical utilization of fixed frequency spectrum.

    Cons:   

• The system is more complicated.
• Guard band and guard time both are required to be provided.
• As the number of users increases, the overall quality of services decreases.