Example Forward Error Correction Tutorial
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(Discuss) Proposed since January 2015. In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel how forward error correction works coding[1] is a technique used for controlling errors in data what is forward error correction used for transmission over unreliable or noisy communication channels. The central idea is the sender encodes the message forward error control in a redundant way by using an error-correcting code (ECC). The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first forward error control coding error-correcting code in 1950: the Hamming (7,4) code.[2] The redundancy allows the receiver to detect a limited number of errors that may occur anywhere in the message, and often to correct these errors without retransmission. FEC gives the receiver the ability to correct errors without needing a reverse channel to request
Fec Signal
retransmission of data, but at the cost of a fixed, higher forward channel bandwidth. FEC is therefore applied in situations where retransmissions are costly or impossible, such as one-way communication links and when transmitting to multiple receivers in multicast. FEC information is usually added to mass storage devices to enable recovery of corrupted data, and is widely used in modems. FEC processing in a receiver may be applied to a digital bit stream or in the demodulation of a digitally modulated carrier. For the latter, FEC is an integral part of the initial analog-to-digital conversion in the receiver. The Viterbi decoder implements a soft-decision algorithm to demodulate digital data from an analog signal corrupted by noise. Many FEC coders can also generate a bit-error rate (BER) signal which can be used as feedback to fine-tune the analog receiving electronics. The noisy-channel coding theorem establishes bounds on the theoretical maximum information transfer r
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Fec And Ecc
machen Schließen Dieses Video ist nicht verfügbar. WiedergabelisteWarteschlangeWiedergabelisteWarteschlange Alle entfernenBeenden Wird forward error correction ppt geladen... Wiedergabeliste Warteschlange __count__/__total__ Forward error correction WikiAudio AbonnierenAbonniertAbo beenden2.0392 Tsd. Wird geladen... Wird geladen... Wird verarbeitet... forward error correction 3/4 Hinzufügen Möchtest du dieses Video später noch einmal ansehen? Wenn du bei YouTube angemeldet bist, kannst du dieses Video zu einer Playlist hinzufügen. Anmelden Teilen Mehr Melden Möchtest https://en.wikipedia.org/wiki/Forward_error_correction du dieses Video melden? Melde dich an, um unangemessene Inhalte zu melden. Anmelden Transkript Statistik 1.009 Aufrufe 0 Dieses Video gefällt dir? Melde dich bei YouTube an, damit dein Feedback gezählt wird. Anmelden 1 8 Dieses Video gefällt dir nicht? Melde dich bei YouTube an, damit dein Feedback gezählt wird. Anmelden 9 Wird geladen... Wird geladen... https://www.youtube.com/watch?v=8VhAnTlQuPE Transkript Das interaktive Transkript konnte nicht geladen werden. Wird geladen... Wird geladen... Die Bewertungsfunktion ist nach Ausleihen des Videos verfügbar. Diese Funktion ist zurzeit nicht verfügbar. Bitte versuche es später erneut. Veröffentlicht am 22.01.2016Forward error correction In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels.The central idea is the sender encodes the message in a redundant way by using an error-correcting code (ECC).-Video is targeted to blind usersAttribution:Article text available under CC-BY-SAimage source in videohttps://www.youtube.com/watch?v=8VhAn... Kategorie Bildung Lizenz Standard-YouTube-Lizenz Mehr anzeigen Weniger anzeigen Wird geladen... Anzeige Autoplay Wenn Autoplay aktiviert ist, wird die Wiedergabe automatisch mit einem der aktuellen Videovorschläge fortgesetzt. Nächstes Video Error Detection and Correction 3: Forward Error Correction - Dauer: 13:28 Jacob Schrum 854 Aufrufe 13:28 How do error correction codes work? (Hamming coding) - Dauer: 5:25 Art of the Problem 25.712 Aufrufe 5:25 Optical communication systems with soft-decision FEC: r
of Block code is BCH code. As other block code, BCH encodes k data bits into n code bits by adding n-k parity checking bits for the purpose of detecting and checking the errors. Given the length of the codes is for http://www.ecs.umass.edu/ece/koren/FaultTolerantSystems/simulator/BCH/FEC.htm any integer m3, we will have t (where t<), is the bound of the error correction. http://www.tech-faq.com/forward-error-correction-fec.html That is, BCH can correct any combination of errors (burst or separate) fewer than t in the n-bit-codes. The number of parity checking bits is n-kmt. An important concept for BCH is Galois Fields (GF), which is a finite set of elements on which two binary addition and multiplication can be defined. For any prime number p there is GF(p) and GF(is forward error called extended field of GF(p). We often use GF(in BCH code. A GF can be constructed over a primitive polynomial such as (The construction and arithmetic of GF are in Error Control Coding, by Shu Lin). Usually, GF table records all the variables, including expressions for the elements, minimal polynomial, and generator polynomial. By referring to the table, we can locate a proper generator polynomial for encoder. For example, when (n, k, t)=(15, 7, 2), a possible generator is forward error correction . If we have a data stream, the codeword would be and have the style of . The decoder of BCH is complicated because it has to locate and correct the errors. Suppose we have a received codeword, then , where, v(x) is correct codeword and e(x) is the error. First, we must compute a syndrome vector s=, which can be achieved by calculating, where, H is parity-check matrix and can be defined as: . Here,is the element of the GF field and can be located in the GF table. With syndrome, error-location polynomial can be determined. Berkekamps iterative algorithm is one of solutions to calculate the error-location polynomial. By finding roots of, the location numbers for the errors will be achieved. Usage The program is developed with Java applet. Basically, the implementation involves three steps: Encoder, Error adding, Decoder. Encoder m and t are available for adjusting. As mentioned above, the codeword length will be. t is the bound of error correction. With m and t being settled, the length of data bits is k=n-mt. Although the program itself has no boundary for m, considering the display limitation, m will be set between 3 and 7. The range checking for m and t are available, if m and t are set to unreasonable values, a red color will be filled input area and program wil
need for retransmission. How Forward Error Correction Works FEC works by adding “check bits” to the outgoing data stream. Adding more check bits reduces the amount of available bandwidth by increasing the overall block size of the outgoing data, but also enables the receiver to correct for more errors without receiving any additional transmitted data. This dynamic makes FEC ideal when bandwidth is plentiful, but retransmission is costly or impossible. The “check bits,” or redundant bits, that the sender adds to the data stream are coded into the data in a very specific way, which allows for efficient error correction by the receiving device. Many different types of FEC coding have been developed. A simplistic example would be a triple redundancy code, also known as (3,1) repetition code, where each bit of data is simply transmitted 3 times. The results of each triplet are averaged together to account for noise in the transmission, and a corrected result is decided on. Other more advanced coding systems that are in use today include Reed-Solomon coding, a customizable coding scheme that is often used in DVB. Applications of Forward Error Correction Reed-Solomon coding is notable for its use in CD, DVD, and hard disk drives. Although these drives are not transmitting data in the traditional sense, FEC coding allows for error correction on bits that become corrupted through damage to the physical medium of the drive. Many types of multicast transmissions also make use of FEC. Forward Error Correction is particularly well suited for satellite transmissions, both for consumer and space exploration applications, where bandwidth is reasonable but latency is significant. Forward Error Correction vs. Backward Error Correction Forward Error Correction protocols impose a greater bandwidth overhead than backward error correction protocols, but are able to recover from errors more quickly and with significantly fewer retransmissions. Forward Error Correction also places a higher computational demand on the receiving device because the redundant information in the transmission must be interpreted according to a predetermined algorithm. Overall,