Basic Components of data communication are:
Source: It is the transmitter of data. Examples are: Terminal, Computer, Mainframe etc.
Medium: The communications stream through which the data is being transmitted. Examples are: Cabling, Microwave, Fiber optics, Radio Frequencies (RF), Infrared Wireless etc.
Receiver: The receiver of the data transmitted. Examples are: Printer, Terminal, Mainframe, and Computer.
Above figure shows the basic block diagram of a typical data communication system. This can further be broken down to three; the source system, transmission system and destination system.
The source generates the information or data that will be transmitted to the destination. Popular forms of information include text, numbers, pictures, audio, video or a combination of any of these.
Information are put together in analog or digital form and broken into group or segment of data called packets. Each packet consists of the following:
- the actual data being sent
- information about the type of data
- where the data came from
- where it is going, and
- how it should be reassembled so the message is clear and in order when it arrives at the destination.
The transmitter a device used to convert the data as per the destination requirement.
For example a modem, converts the analog (telephonic) signal to digital (computer) signals and alternatively digital to analog.
3. Transmission medium
The transmission medium is the physical path by which data travels from transmitter to receiver.
For Example of such channels is copper wires, optical fibers and wireless communication channels etc.
This receives the signals from the transmission medium and converts it into a form that is suitable to the destination device.
For example, a modem accepts analog signal from a transmission channel and transforms it into digital bit stream which is acceptable by computer system.
It is simply a device for which source device sends the data.
Data Communication Criteria
The effectiveness of data communications system depends on four fundamental characteristics:
The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.
The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.
The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real – time transmission and this occurs in a real – time system.
Jitter refers to the variation in the packet arrival time. It is the uneven delay of delivery of audio or video packets.
For example, let us assume that video packets are sent every 20ms. If some of the packets arrive with 20ms delay and others with 30ms delay, an uneven quality in the video is the result.