Forward Error Correction(FEC)
Introduction: In modern communication systems, information is digitized, coded to logic levels “1” and “0” and often further encoded into complex modulation schemes such as Pulse Amplitude Modulation (PAM) or Quadrature Amplitude Modulation (QAM). Integrity of the information at the received end can be critical, so it is essential that any errors can be avoided, and if not, repaired. When major errors occur in the transmitted data, such as where significant parts of the data is missing, or the frame looks very different from what is expected, Equipment Management Systems can determine a problem and manage it accordingly. But, minor errors, where only a small number of bits in the frame are corrupt, the data looks the same to the system and errors are therefore not so easily spotted. One single error can be enough to cause the meaning of the message to be drastically altered, but the system has no way of knowing it. The diagram shows the voltage transition from lo