Data communication
Data communication, including data transmission and data reception, is the transfer of
signal.Analog transmission is a method of conveying voice, data, image, signal or video information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that of a variable. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying waveforms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation is carried out by modem equipment.
Digital communications, including digital transmission and digital reception, is the transfer of either a
Courses and textbooks in the field of data transmission[1] as well as digital transmission[2][3] and digital communications[4][5] have similar content.
Digital transmission or data transmission traditionally belongs to
In most textbooks, the term
The theoretical aspects of data transmission are covered by information theory and coding theory.
Protocol layers and sub-topics
OSI model by layer |
---|
Courses and textbooks in the field of data transmission typically deal with the following OSI model protocol layers and topics:
- Layer 1, the physical layer:
- Channel codingincluding
- Digital modulationschemes
- Line codingschemes
- Forward error correction(FEC) codes
- Bit synchronization
- Multiplexing
- Equalization
- Channel models
- Layer 2, the data link layer:
- media access control(MAC)
- Packet mode communication and Frame synchronization
- Error detection and automatic repeat request(ARQ)
- Flow control
- Layer 6, the presentation layer:
- Source coding(digitization and data compression), and information theory.
- Cryptography (may occur at any layer)
It is also common to deal with the cross-layer design of those three layers.[7]
Applications and history
Data (mainly but not exclusively
Data transmission is utilized in
In telephone networks, digital communication is utilized for transferring many phone calls over the same copper cable or fiber cable by means of
Transmitting analog signals digitally allows for greater signal processing capability. The ability to process a communications signal means that errors caused by random processes can be detected and corrected. Digital signals can also be sampled instead of continuously monitored. The multiplexing of multiple digital signals is much simpler compared to the multiplexing of analog signals. Because of all these advantages, because of the vast demand to transmit computer data and the ability of digital communications to do so and because recent advances in wideband communication channels and solid-state electronics have allowed engineers to realize these advantages fully, digital communications have grown quickly.
The digital revolution has also resulted in many digital telecommunication applications where the principles of data transmission are applied. Examples include
Data transmission, digital transmission or digital communications is the transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels include copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data are represented as an
While analog transmission is the transfer of a continuously varying analog signal over an analog channel, digital communication is the transfer of discrete messages over a digital or an analog channel. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment. According to the most common definition of a digital signal, both baseband and passband signals representing bit-streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital-to-analog conversion.[citation needed]
Data transmitted may be digital messages originating from a data source, for example a computer or a keyboard. It may also be an analog signal such as a phone call or a video signal, digitized into a bit-stream for example using pulse-code modulation (PCM) or more advanced source coding (analog-to-digital conversion and data compression) schemes. This source coding and decoding is carried out by codec equipment.
Serial and parallel transmission
In telecommunications,
Parallel transmission is the simultaneous transmission of related signal elements over two or more separate paths. Multiple electrical wires are used which can transmit multiple bits simultaneously, which allows for higher data transfer rates than can be achieved with serial transmission. This method is typically used internally within the computer, for example, the internal buses, and sometimes externally for such things as printers.
Communication channels
Some communications channel types include:
- Data transmission circuit
- Full-duplex
- Half-duplex
- Simplex
- Multi-drop:
- Bus network
- Mesh network
- Ring network
- Star network
- Wireless network
- Point-to-point
Asynchronous and synchronous data transmission
Asynchronous serial communication uses start and stop bits to signify the beginning and end of transmission.[9] This method of transmission is used when data are sent intermittently as opposed to in a solid stream.
See also
- Internetworking
- Media (communication)
- Network security
- Node-to-node data transfer
- Transmission (disambiguation)
References
- ^ a b c A. P. Clark, "Principles of Digital Data Transmission", Published by Wiley, 1983
- ISBN 1-4020-7587-1. See table-of-contents.
- ISBN 978-0-306-45753-1. See table-of-contents
- ISBN 978-0-471-62947-4. See table-of-contents.
- ISBN 0-07-232111-3. See table-of-contents.
- ^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.
- ^ F. Foukalas et al., "Cross-layer design proposals for wireless mobile networks: a survey and taxonomy "
- ^ Barker, RH (1953). Group Synchronisation of Binary Digital Systems. Communication Theory: Butterworth. pp. 273–287.
- ^ "What is Asynchronous Transmission? - Definition from Techopedia". Techopedia.com. Retrieved 2017-12-08.