Analog signal data has been sent electronically since the advent of the telephone. optical, acoustic, mechanical) means since the advent of communication.
Applications and history ĭata (mainly but not exclusively informational) has been sent via non-electronic (e.g. It is also common to deal with the cross-layer design of those three layers.
Source coding (digitization and data compression), and information theory.Error detection and automatic repeat request (ARQ).Packet mode communication and Frame synchronization.Channel access schemes, media access control (MAC).Protocol layers and sub-topics OSI modelĬourses and textbooks in the field of data transmission typically deal with the following OSI model protocol layers and topics: The theoretical aspects of data transmission are covered by information theory and coding theory. Note that these methods are covered in textbooks named digital transmission or data transmission, for example. In a few books within the computer networking tradition, analog transmission also refers to passband transmission of bit-streams using digital modulation methods such as FSK, PSK and ASK. It may also include analog-over-analog pulse modulatated baseband signals such as pulse-width modulation. In most textbooks, the term analog transmission only refers to the transmission of an analog message signal (without digitization) by means of an analog signal, either as a non-modulated baseband signal or as a passband signal using an analog modulation method such as AM or FM. 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. 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. 6 Asynchronous and synchronous data transmissionĭistinction between related subjects Ĭourses and textbooks in the field of data transmission as well as digital transmission and digital communications have similar content.ĭigital transmission or data transmission traditionally belongs to telecommunications and electrical engineering.This source coding and decoding is carried out by codec equipment. 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 or more advanced source coding schemes. According to the most common definition of 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.ĭata transmitted may be digital messages originating from a data source, for example, a computer or a keyboard. The passband modulation and corresponding demodulation is carried out by modem equipment.
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 data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.Īnalog 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. Examples of such channels are copper wires, optical fibers, wireless communication using radio spectrum, storage media and computer buses. For broader coverage of this topic, see Communication.ĭata transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal over a point-to-point or point-to-multipoint communication channel.