What is baseband transmission in computer networks?

Digital Modulation is the process of converting between bits and signals.

Transmission Mechanisms

The various modulation schemes result in various transmission mechanisms which are as follows −

  • Baseband transmission.
  • Passband transmission.

Multiplexing Techniques

Sharing of a transmission channel by various signals is called multiplexing. The different multiplexing techniques are as follows −

  • Time division multiplexing.
  • Frequency division multiplexing.
  • Code division multiplexing.

Now, let us discuss one of the digital modulation schemes.

Baseband Transmission

Baseband transmission is transmission of the encoded signal using its own baseband frequencies i.e. without any shift to higher frequency ranges. It is used for short distances.

Steps in Baseband Transmission

Let us understand the baseband transmission step by step.

Step 1 − The most straightforward form of digital modulation is to use a positive voltage which represents ‘1’ and negative voltage represents ‘0’.

Step 2 − For an optical signal the presence of light may represent ‘1’ and absence of light represent ‘0’. This scheme is called NRZ (Non-Return-to-Zero).

Step 3 − Once sent, the NRZ signal propagates down the wire.

Step 4 − At the other end, the receiver converts it into bits by sampling the signal at regular intervals of time.

Step 5 − This signal will not look exactly like the signal that was sent.

Step 6 − It will be attenuated and distorted by the channel and noise at the receiver.

Step 7 − To decode the bits, the receiver maps the signal samples to the closest symbols.

Step 8 − For NRZ, a positive voltage will be taken to indicate that ‘1’ was sent and negative voltage will be taken to indicate that ‘0’ was sent.

Step 9 − NRZ is a good starting point for studies because it is simple.

Step 10 − In practice, it is rarely used by itself.

Step 11 − More complex schemes can convert bits to signals that better meet engineering considerations.

Step 12 − These schemes are called line codes.

Step 13 − Line codes help with −

  • Bandwidth efficiency.
  • Clock recovery.
  • DC balance.

The baseband transmission is pictorially represented as follows −