Introduction to Communication Systems

History of Communication

In the past, message have been carried by:

• Runners
• Carrier pigeons
• Drum beats  & torches.

These schemes were adequate for the short distances ranges.

Nowadays, they are replaced by electrical communication systems which can transmit signals over much longer distances at the speed of light.

Advantages: Reliable and economical, alleviate energy crisis e.g., teleconferencing, teleshopping, telebanking. (electronic communication & electronic news service).

• Samuel S.B. Morse sent the first telegraph message over a 16km line in 1838.
• A new era was born –  the era of electrical communication.
• Long distance circuits span the globe carrying text, data, voice and image.
• Computers talk to computers via intercontinental networks.
• Electronic communication system is the transmission, reception and processing of information between two or more entities located at different places using electrical/electronic circuits.

Significance of Human Communication

Methods of communication:

1.Face to face

2.Signals

3.Written word (letters)

4.Electrical innovations:

• Telegraph
• Telephone
• Radio
• Television
• Internet (computer)

Elements of Electronic communication systems

Main purpose of electronic communication is to transfer information from a source to a recipient via a channel or medium.

Basic components of electronic communication are:

• Transmitter
• Channel or medium
• Receiver

Noise degrades or interferes with transmitted information.

General block diagram of communication system is shown below.

The source originates a message such as:

• Human voice
• A television picture or (Video) , Music
• Data, E-mail

Input transducer converts the data from the source in to electrical signal (baseband signal or  message signal).

Transmitter modifies the baseband signal for efficient transmission.

The channel is a medium (coaxial cable, a waveguide, an optical fiber or radio link) through which transmitter output is sent.

The receiver reprocesses the signal received from the channel by undoing the signal modification made at the transmitter and the channel.

The Output transducer converts the electrical signal back to its original form (the message).

The destination the unit to which the message is communicated, e.g. person, (loud) speaker, Computer

The channel-attenuate the signal and distorts the signal.

Contaminated by  undesirable signal (noise). Noise is random, undesirable electronic energy that enters the communication system via the communicating medium and interferes with the transmitted message.

The signal strength decreases  while the noise increases along the path.