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CRC + FEC = Error Detection and Correction (anglais seulement) |
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Most Power line Carrier systems and technologies offer some kind of error detection technique, (like Cyclic Redundancy Check or CRC) so that erroneous packets are not interpreted. For example, the CEBus PLC Standard includes an excellent CRC-based error detection algorithm for PL medium, but has no forward error correction. To further enhance the possibility of reliable communication in hostile environments requires appropriate signaling schemes and error control strategies. It is well known that Forward Error Correction(FEC) techniques [5] can significantly improve communication reliability.
Simply stated, FEC adds redundant information to the original message, allowing the receiver to retrieve the message even if it contains erroneous bits. Nowadays FEC is everywhere around us; it is extensively used in many (if not most) digital communication systems, in Compact Disk technology, (to tolerate scratched CDs), in satellite communications, etc… Unfortunately, only a few PLC technologies offer an efficient Forward Error Correction algorithm, combined with an error detection scheme. Facing line synchronous error bursts, (and particularly when item 4 above is involved) typical non-FEC systems are often unable to deliver any usable data. They only detect that the message has one or more errors, but are unable to correct the erroneous bit(s) in the received packet, and reject the data packet.
References :
[5] S. Lin and D.J. Costello, Jr., "Error Control Coding : Fundamentals and applications." Englewood Cliffs, N.J. : Prentice-Hall, 1983
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