Automatic Repeat Request Vs Forward Error Correction
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Arq Vs Fec
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- Once Detected, an error must be corrected.
- Two basic approaches to error correction are available, which are:
- Automatic-repeat-request (ARQ):
- Forward error correction (FEC): 3. 4.2.3 Error Correction
- Automatic-repeat request (ARQ):
- ARQ procedures require the transmitter to resend the portions of the exchange in which error have been detected.
- Forward error correction (FEC):
- FEC techni
(Discuss) Proposed since January 2015. In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding[1]
Error Detection And Correction Using Hamming Code Example
is a technique used for controlling errors in data transmission over difference between forward error correction and automatic repeat request unreliable or noisy communication channels. The central idea is the sender encodes the message in forward error correction techniques 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 error-correcting code http://www.slideshare.net/leopk01/error-correction-arq-fec 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 retransmission of data, but https://en.wikipedia.org/wiki/Forward_error_correction 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 rate of a channel with some given noise
Hardware Configuration -- 8250 UART -- DOS -- MAX232 Driver/Receiver Family -- TAPI Communications In Windows -- Linux and Unix -- Java -- Hayes-compatible Modems and AT Commands -- Universal Serial Bus (USB) -- Forming Data Packets -- Error Correction Methods -- Two Way Communication -- https://en.wikibooks.org/wiki/Serial_Programming/Error_Correction_Methods Packet Recovery Methods -- Serial Data Networks -- Practical Application Development -- IP Over Serial Connections http://www.google.com/patents/US7904779 Contents 1 Introduction 2 ACK-NAK 2.1 How does the receiver know it's good? 2.2 How does the sender know it wasn't good? 2.3 "Stop-and-wait ARQ" 2.4 streaming ARQ 2.5 Selective Repeat ARQ 3 FEC 4 Pretend It Never Happened 5 combination 6 further reading 7 further reading Introduction[edit] There are 3 main types of handling errors: acknowledge or retry (ACK-NAK). "Forward Error Correction" error correction (FEC) Pretend It Never Happened ACK-NAK[edit] Each packet is checked by the receiver to make sure it is "good". If it *is* good, the receiver (eventually) tells the sender that it came through OK -- it acknowledges (ACK) the packet. All versions of ACK-NAK absolutely require Two Way Communication . How does the receiver know it's good?[edit] The sender calculates a checksum or CRC for the entire packet (except for the footer), then appends it to the end of forward error correction the packet (in the footer/trailer). The typical CRC is 32 bits, often a Fletcher-32 checksum. Aside: Note that the checksum or CRC are forms of hashing, ie, irreversibly shrinking data. Checksums and CRCs are weaker algorithms than "cryptographically strong" message authentication code algorithms such as MD5 or SHA variants. Cryptographically strong algorithms can detect errors better than checksums or CRCs, but they take more time to calculate. Whenever the receiver receives a packet, the receiver calculates exactly the same checksum or CRC, then compares it to the one in the footer/trailer. If they match, the entire packet is (almost certainly) good, so the receiver sends an ACK. When there's even the slightest question that the packet has any sort of error (which could be *either* in the actual data *or* in the header *or* in the checksum bits -- there's no way for the receiver to tell), the receiver discards it completely and (in most cases) pretends it never saw it. If it's not good, the sender sends it again. How does the sender know it wasn't good?[edit] It never got the ACK. (So either the packet was corrupted, *or* the ACK was corrupted -- there's no way for the sender to know). "Stop-and-wait ARQ"[edit] The simplest version of ACK-NAK is "Stop-and-wait ARQ". The sender sends a packet, then waits a little for an ACK. As soon as it gets the ACK, it immediately sends t
a communication signal. Joint operation of forward error correction (FEC) techniques and automatic repeat request (ARQ) techniques are conducted above a physical layer of a communication network. Forward error correction is applied if the number...http://www.google.com/patents/US7904779?utm_source=gb-gplus-sharePatent US7904779 - Forward error correction and automatic repeat request joint operation for a data link layerAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7904779 B2Publication typeGrantApplication numberUS 11/576,296PCT numberPCT/RU2004/000535Publication dateMar 8, 2011Filing dateDec 29, 2004Priority dateDec 29, 2004Fee statusPaidAlso published asCN101091347A, CN101091347B, DE112004003036T5, US20080022181, WO2006073323A1Publication number11576296, 576296, PCT/2004/535, PCT/RU/2004/000535, PCT/RU/2004/00535, PCT/RU/4/000535, PCT/RU/4/00535, PCT/RU2004/000535, PCT/RU2004/00535, PCT/RU2004000535, PCT/RU200400535, PCT/RU4/000535, PCT/RU4/00535, PCT/RU4000535, PCT/RU400535, US 7904779 B2, US 7904779B2, US-B2-7904779, US7904779 B2, US7904779B2InventorsAndrey Vladimirovich Belogolovy, Evguenii Avramovich KroukOriginal AssigneeIntel CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (6), Non-Patent Citations (4), Referenced by (9), Classifications (10), Legal Events (2) External Links:USPTO, USPTO Assignment, EspacenetForward error correction and automatic repeat request joint operation for a data link layer US 7904779 B2Abstract A method and apparatus are provided for error correction of a communication signal. Joint operation of forward error correction (FEC) techniques and automatic repeat request (ARQ) techniques are conducted above a physical layer of a communication network. Forward error correction is applied if the number of errors is equal to or less than an error threshold. Automatic repeat request techniques are applied if errors remain in the data decoding using the forward error correction or if an
- FEC techni
- Forward error correction (FEC):
- ARQ procedures require the transmitter to resend the portions of the exchange in which error have been detected.
- Automatic-repeat request (ARQ):
- Forward error correction (FEC): 3. 4.2.3 Error Correction
- Automatic-repeat-request (ARQ):
- Two basic approaches to error correction are available, which are: