Data communication

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"Data transfer" redirects here. For sharing data between different programs or schemas, see Data exchange.
"Digital communication" redirects here. For the sociological aspects, see Computer-mediated communication.
For broader coverage of this topic, see Communication.

Data communication, including data transmission and data reception, is the transfer of

radiowave, microwave, or infrared
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

digital-to-analog conversion
.

Distinction between related subjects

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

telecommunications and electrical engineering. Basic principles of data transmission may also be covered within the computer science or computer engineering topic of data communications, which also includes computer networking applications and communication protocols, for example routing, switching and inter-process communication. Although the Transmission Control Protocol
(TCP) involves transmission, TCP and other transport layer protocols are covered in computer networking but not discussed in a textbook or course about data transmission.

In most textbooks, the term

digital modulation methods such as FSK, PSK and ASK. Note that these methods are covered in textbooks named digital transmission or data transmission, for example.[1]

The theoretical aspects of data transmission are covered by information theory and coding theory.

Protocol layers and sub-topics

OSI model
by layer
7.  Application layer
6.  Presentation layer
5.  Session layer
4.  Transport layer
3.  Network layer
2.  Data link layer
1.  Physical layer

Courses and textbooks in the field of data transmission typically deal with the following OSI model protocol layers and topics:

It is also common to deal with the cross-layer design of those three layers.[7]

Applications and history

Data (mainly but not exclusively

digital signals. The fundamental theoretical work in data transmission and information theory by Harry Nyquist, Ralph Hartley, Claude Shannon
and others during the early 20th century, was done with these applications in mind.

Data transmission is utilized in

microwave links, wireless network access points
(1997), etc.

In telephone networks, digital communication is utilized for transferring many phone calls over the same copper cable or fiber cable by means of

IPTV
.

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

digital TV (1998), digital radio (1999), and telemetry
.

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

electromagnetic signal
, such as an electrical voltage, radiowave, microwave, or infrared light.

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,

transfer rate of each individual path may be faster. This can be used over longer distances and a check digit or parity bit
can be sent along with the data easily.

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.

Timing skew
can be a significant issue in these systems because the wires in parallel data transmission unavoidably have slightly different properties so some bits may arrive before others, which may corrupt the message. This issue tends to worsen with distance making parallel data transmission less reliable for long distances.

Communication channels

Main article: Communication channel

Some communications channel types include:

Asynchronous and synchronous data transmission

Main article: Comparison of synchronous and asynchronous signalling

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.

Synchronous transmission synchronizes transmission speeds at both the receiving and sending end of the transmission using clock signals. The clock may be a separate signal or embedded in the data
. A continual stream of data is then sent between the two nodes. Due to there being no start and stop bits, the data transfer rate may be more efficient.

See also

References

  1. ^ a b c A. P. Clark, "Principles of Digital Data Transmission", Published by Wiley, 1983
  2. ISBN 1-4020-7587-1. See table-of-contents
    .
  3. ISBN 978-0-306-45753-1. See table-of-contents
  4. ISBN 978-0-471-62947-4. See table-of-contents
    .
  5. ISBN 0-07-232111-3. See table-of-contents
    .
  6. ^ "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.
  7. ^ F. Foukalas et al., "Cross-layer design proposals for wireless mobile networks: a survey and taxonomy "
  8. ^ Barker, RH (1953). Group Synchronisation of Binary Digital Systems. Communication Theory: Butterworth. pp. 273–287.
  9. ^ "What is Asynchronous Transmission? - Definition from Techopedia". Techopedia.com. Retrieved 2017-12-08.
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