Editing Node-to-node data transfer

{{more citations needed|date=July 2022}}
In [[telecommunications]], '''node-to-node data transfer'''<ref>{{Cite web |title=Node-to-Node Data Transfers |url=https://www.intel.com/content/www/us/en/develop/documentation/application-snapshot-user-guide/top/detailed-analyses/mpi-analyses/analysis-charts/node-to-node-data-transfers.html |access-date=2022-07-22 |website=Intel |language=en}}</ref> is the movement of data from one [[node (networking)|node]] of a [[Telecommunications network|network]] to the next. In the [[OSI model]] it is handled by the lowest two layers, the [[data link layer]] and the [[physical layer]].

In most communication systems, the transmitting point applies [[source coding]],<ref>{{Cite web |title=Information and Communication Theory Source Coding Techniques -PART -II Handbook on Source Coding Techniques -Part II |url=https://www.researchgate.net/publication/358285643}}</ref> followed by [[channel coding]], and lastly, [[line coding]]. This produces the [[baseband]] signal. The presence of filters may perform [[pulse shaping]]. Some systems then use [[modulation]] to multiplex many baseband signals into a [[broadband]] signal. The receiver un-does these transformations in reverse order: demodulation, trellis decoding, error detection and correction, decompression.

Some communication systems omit one or more of these steps, or use techniques that combine several of these steps together. For example, a [[Morse code]] transmitter combines source coding, channel coding, and line coding into one step, typically followed by an [[amplitude modulation]] step. [[Barcode]]s, on the other hand, add a checksum digit during channel coding, then translate each digit into a barcode symbol during line coding, omitting modulation.

==Source coding==
:''See main article [[Data compression]]''

Source coding is the elimination of redundancy to make efficient use of storage space and/or transmission channels.{{citation needed|date=July 2022}}

Examples of '''source coding''' are: 
*[[Huffman coding]]
*[[Morse code]]
*[[Binary coding]]

==Channel coding==
:''See main article [[Error correction and detection]].''

In [[Digital data|digital]] [[telecommunications]], '''channel coding'''<ref>{{Cite journal |title=Comparison between Different Channel Coding Techniques for IEEE 802.11be within Factory Automation Scenarios |year=2021 |pmc=8587646 |last1=Fanari |first1=L. |last2=Iradier |first2=E. |last3=Bilbao |first3=I. |last4=Cabrera |first4=R. |last5=Montalban |first5=J. |last6=Angueira |first6=P. |journal=Sensors (Basel, Switzerland) |volume=21 |issue=21 |page=7209 |doi=10.3390/s21217209 |pmid=34770516 |bibcode=2021Senso..21.7209F |doi-access=free }}</ref> is a pre-transmission mapping applied to a [[Digital signal (signal processing)|digital signal]] or data file, usually designed to make error-correction (or at least [[Error-detecting code|error detection]]) possible.

Error correction is implemented by using more [[numerical digit|digit]]s ([[bit]]s in cases of binary channel) than the number strictly necessary for the samples and having the receiver compute the most likely valid message that could have resulted in the received one.

Types of '''channel coding''' include:
*[[Parity check]]s
*[[Hamming code]]
*[[Reed-Muller code]] 
*[[Reed-Solomon code]] 
*[[Turbo coding]]

==Line coding==
:''See main article [[Line code]]''

'''Line coding''' consists of representing the [[Digital signal (electronics)|digital signal]] to be transported, by an amplitude- and time-discrete signal, that is optimally tuned for the specific properties of the physical channel (and of the receiving equipment). The [[waveform]] pattern of voltage or current used to represent the 1s and 0s of a digital signal on a transmission link is called '''''line encoding'''''. 
After line coding, the signal can directly be put on a transmission line, in the form of variations of the current. The common types of line encoding are [[Unipolar encoding|unipolar]], [[Polar encoding|polar]], [[Bipolar encoding|bipolar]] and [[Manchester encoding]].

Line coding should make it possible for the receiver to synchronise itself to the [[phase (waves)|phase]] of the received signal. It is also preferred for the line code to have a structure that will enable error detection.

Examples of '''line coding''' include:
''(see main article [[line code]])''
*[[B8ZS]]
*[[HDB3]]
*[[2B1Q]]
*[[Alternate Mark Inversion|AMI]]
*[[Gray coding]]

==Modulation==
{{main|Modulation}}

'''Modulation''' is the process of varying a ''[[carrier signal]]'', typically a [[sine wave]] to use that signal to convey [[information]]. One of the three key characteristics of a signal are usually modulated: its [[phase (waves)|phase]], [[frequency]] or [[amplitude]].

In [[Digital data|digital]] modulation, the changes in the signal are chosen from a fixed list (the '''modulation alphabet''') each entry of which conveys a different possible piece of information (a symbol). In [[analog signal|analogue]] modulation, the change is applied continuously in response to the data signal.

Modulation is generally performed to overcome signal transmission issues such as to allow
* Easy (low loss, low dispersion) [[Wave propagation|propagation]] as [[electromagnetic wave]]s
* [[Multiplexing]], the transmission of multiple data signals in one frequency band, on different [[Carrier signal|carrier]] frequencies.
* Smaller, more [[directional antenna]]s

Carrier signals are usually high frequency electromagnetic waves.

Examples of '''modulation''' include:
*[[amplitude modulation]]
*[[frequency modulation]]
*[[Phase-shift keying]]

==See also==
* [[Communication channel]]
* [[Data link]]
* [[Data transmission]]
* [[Point-to-point (telecommunications)]]

==References==
{{Reflist}}

[[Category:Data transmission]]