In computing and telecommunications, communication is the exchange of data between computers through a connection. In order for computers to understand each other there must be a common «language» called protocols.
For more information I suggest reading the articles:
– Telecommunications and telecommunications network
– Data transfer
– data transmission speed
Communication as data transmission
Data transmission (also data communication or digital communications) is the transfer of data (a digital bit stream or a digitized analog signal) over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper cables, fiber optics, wireless communication channels, storage media, and computer buses. The data is represented as an electromagnetic signal, such as an electrical voltage, a radio wave, a microwave, or an infrared signal.
Analog transmission is a method of transmitting voice, data, images, signals, or video information that uses a continuous signal that varies in amplitude, phase, or other property in proportion to that of a variable. Messages are represented by a sequence of pulses using a line code (baseband transmission) or by a limited set of continuously varying waveforms (passband transmission), using a digital modulation method. Bandpass modulation and corresponding demodulation is carried out by modem equipment. Under the most common definition of a digital signal, both baseband and passband signals representing binary streams are considered digital transmission, while an alternative definition considers only the baseband signal to be digital, and the passband transmission as digital. of digital data as a form of digital-to-analog conversion.
The transmitted data may be digital messages from a data source, eg, a computer or keyboard. It can also be an analog signal, such as a telephone call or a video signal, digitized into a bit stream, for example, using pulse code modulation (PCM) or more advanced source coding schemes (analog-to-digital conversion and compression). of data). This encoding and decoding of the source is done by a team of codecs.
History of data transmission and applications
Data (mainly, but not exclusively informational) has been sent by non-electronic means (eg optical, acoustic, mechanical) since the arrival of the communication. The analog signal data has been sent electronically since the arrival of the telephone. However, the first applications of electromagnetic data transmission in the modern era were telegraphy (1809) and teletypes (1906), which are digital signals. The seminal theoretical work in data transmission and information theory by Harry Nyquist, Ralph Hartley, Claude Shannon, and others during the early years of the 20th century was done with these applications in mind.
Data transmission is used in computers on computer buses and for communication with peripheral equipment through parallel ports and serial ports such as RS-232 (1969), Firewire (1995), and USB (1996). The principles of data transmission have also been used in storage media for error detection and correction since 1951.
Data transmission is used in computer networking equipment such as modems (1940), local area network (LAN) adapters (1964), repeaters, repeater hubs, microwave links, wireless network access points (1997), etc.
In telephone networks, digital communication is used to transfer many telephone calls over the same copper or fiber cable using pulse code modulation (PCM), that is, sampling and digitizing, in combination with time division multiplexing (PCM). TDM) (1962). Telephone exchanges have become digital and are controlled by software, which facilitates many value-added services. For example, the first AX telephone exchange was introduced in 1976. Since the late 1980s, digital communication with the end user has been possible thanks to Integrated Services Digital Network (ISDN) services. Since the late 1990s, broadband access techniques such as ADSL, cable modems, fiber to the building (FTTB), and fiber to the home (FTTH) have spread to small offices and homes. The current trend is to replace traditional telecommunications services with packet mode communication, such as IP telephony and IPTV.
Digital transmission of analog signals allows for greater signal processing capabilities. 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. Multiplexing multiple digital signals is much easier than multiplexing analog signals.
Because of all these advantages, and because recent advances in broadband communication channels and solid-state electronics have enabled scientists to realize these advantages, digital communications has grown rapidly. Digital communications is rapidly moving away from analog communication due to the high demand for computer data transmission and the ability of digital communications to do so.
The digital revolution has also given rise to many digital telecommunications applications where the principles of data transmission are applied. Examples of this are the second generation or 2G (1991) and subsequent cell phones, videoconferences, digital television (1998), digital radio (1999), telemetry, etc.
Data transmission, digital transmission, or digital communications is the physical transfer of data (a digital bit stream or a digitized analog signal) over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper cables, fiber optics, wireless communication channels, storage media, and computer buses. The data is represented as an electromagnetic signal, such as an electrical voltage, a radio wave, a microwave, or an infrared signal.
While analog transmission is the transfer of a continuously varying analog signal over an analog channel, digital communications is the transfer of discrete messages over a digital or analog channel. Messages are represented by a sequence of pulses using a line code (baseband transmission) or by a limited set of continuously varying waveforms (passband transmission), using a digital modulation method. Bandpass modulation and corresponding demodulation (also known as detection) is performed by modem equipment. Under the most common definition of a digital signal, both baseband and passband signals representing binary streams are considered digital transmission, while an alternative definition considers only the baseband signal to be digital, and the passband transmission as digital. of digital data as a form of digital-to-analog conversion.
The transmitted data may be digital messages from a data source, eg, a computer or keyboard. It can also be an analog signal, such as a telephone call or a video signal, digitized into a bit stream, for example, using pulse code modulation (PCM) or more advanced source coding schemes (analog-to-digital conversion). and data compression). This encoding and decoding of the source is done by a team of codecs.
Serial or parallel communication
In telecommunications, serial transmission is the sequential transmission of signal elements from a group that represent a character or other data entity. Digital serial transmissions are bits that are sent down a single wire, frequency, or optical path sequentially. Because it requires less signal processing and less chance of error than parallel transmission, the transfer speed of each individual path can be faster. This can be used over longer distances, as a check digit or parity bit can easily be sent along it.
In telecommunications, parallel transmission is the simultaneous transmission of the signal elements of a character or other data entity. In digital communications, parallel transmission is the simultaneous transmission of related signal elements over two or more separate paths. Multiple electrical wires are used that can transmit multiple bits simultaneously, allowing higher data transfer rates than can be achieved with serial transmission. This method is used internally within the computer, for example the internal buses, and sometimes externally for things like printers. The biggest problem with this is «bias» because the wires in parallel data transmission have slightly different properties (unintentionally), so some bits may arrive before others, which can corrupt the message. A parity bit can help reduce this. However, parallel data transmission over electrical cable is therefore less reliable over long distances, as corrupt transmissions are much more likely.
Synchronous and asynchronous communication
Asynchronous start-stop transmission uses start and stop bits to indicate the beginning and end of transmission. This transmission method is used when data is sent intermittently rather than in a solid stream.
Synchronous transmission synchronizes the transmission rates at both the receiving and sending ends of the transmission using clock signals. The clock can be a separate signal or embedded in the data. A continuous stream of data is then sent between the two nodes. Since there are no start and stop bits, the data transfer rate is more efficient.
Sources:
– communication
– Communication
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