2/3 Forward Error Correction
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(Discuss) Proposed since January 2015. In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding[1] is a technique used for forward error correction 3/4 controlling errors in data transmission over unreliable or noisy communication channels. The
Forward Error Correction Tutorial
central idea is the sender encodes the message in a redundant way by using an error-correcting code forward error correction ppt (ECC). The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first error-correcting code in 1950: the Hamming (7,4) code.[2] The redundancy allows the receiver forward error correction algorithm 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 at the cost of a fixed, higher forward channel bandwidth. FEC is therefore applied in
Forward Error Correction Rate
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 level. Some advanced FEC systems come very close to the theoretical maximum. The maximum fractions of errors or of missing bits that can be corrected is determined by the design
orbit positions EbNo measurement and EbNo Calculator Symbol Rate This page, as an example, refers to the outlink multi-Mbit/s carrier, from the hub, which is shared amongst all VSAT users to download internet web pages etc. The carrier is similar to a DVB-S or DVB-S2 carrier which carries several MPEG TV forward error correction ethernet and audio programmes. The carrier on the satellite is made up of a sequence of joined forward error correction library together pulses to make a continuous signal. Each pulse is a symbol. According to the modulation method each symbol represents 1, 2 or 3 etc
Forward Error Correction Pdf
bits of transmission rate data. In phase shift keying (PSK) modulation each pulse is a burst of carrier signal with its sinewave zero crossing point timing adjusted forwards or backwards in time to constitute a phase shift. Phase shifts of 180 deg https://en.wikipedia.org/wiki/Forward_error_correction apply in BPSK, 90 deg in QPSK etc. A phase shift of 90 deg represents a time shift of 1/4 of a full cycle of the sinewave. The closer the spacing of the phase shifts, the more difficult it is to distinguish between them at the receive end, so for for each higher order PSK schemes more carrier to noise ratio is required.In 16-QAM modulation the amplitude and the phase are changes from symbol to symbol, making a matrix pattern with the dots http://www.satsig.net/symbol01.htm even closer together, and thuis requiring even higher C/N ratio. As a general rule if you have bandwidth to spare, then use a lower order modulation or a higher rate FEC (like 1/2 or 2/3) to spread the signal out. If you have power to spare then use a higher order modulation and/or lower rate FEC (like 3/4 or 7/8). Ideally you want to use all of both the available bandwidth and power simultaneously to obtain the highest user information rate. If you use larger receive dishes you will always be able to increase the system capacity. If you are doing a point to point link it is well worth using larger dishes - spend more on the antennas and used advanced modulation technique modems, like Comtech Vipersat CDM-570L, to save on the space segment costs. If you have thousands of receive dishes then the aggregate cost of these is significant and you will want to allow smaller receive dish sizes even though this reduces system capacity and increases space segment costs. Forward error correction Forward error correction is applied to the customer's information data at the transmit end. so transmission data rate = customer information ratex 1/ (FEC rate). FEC rate is typically in the range 1/2 to 7/8 so thetransmission data rate is always significantly more than thecustomer information rate. This page provides a key formula: SR = Symbol Rate DR = Data Rate =the information rate. This is the same as the customer i
Technology April 2009 Reed-Solomon Forward Error Correction (FEC) Schemes Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and https://tools.ietf.org/html/rfc5510 suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and forward error the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The forward error correction person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Lacan, et al. Standards Track [Page 1] RFC 5510 Reed-Solomon Forward Error Correction April 2009 Abstract This document describes a Fully-Specified Forward Error Correction (FEC) Scheme for the Reed-Solomon FEC codes over GF(2^^m), where m is in {2..16}, and its application to the reliable delivery of data objects on the packet erasure channel (i.e., a communication path where packets are either received without any corruption or discarded during transmission). This document also describes a Fully-Specified FEC Scheme for the special case of Reed-Solomon codes over GF(2
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