Error Management Mechanisms in 4G: FEC, ARQ and HARQ

Error Management Mechanisms : 4G

In the air interface, noise and interference leads to error and it is crucial to manage them to maintain reliable wireless communication. There are three key mechanisms for error management in 4G :-

  • Forward Error Correction (FEC):

    • FEC is a proactive error management technique where redundant information is added to the transmitted data before transmission. This redundant information allows the receiver to detect and correct errors without the need for retransmission. Turbo Codes are commonly used FEC techniques. It provides efficient error correction capabilities, enhancing the reliability of data transmission.
  • Automatic Repeat request (ARQ):

    • ARQ is a reactive error management technique that involves the automatic detection of errors at the receiver, followed by a request for the retransmission of the corrupted data.
      The ARQ process typically involves a feedback mechanism where the receiver informs the transmitter about the successful or unsuccessful reception of a data block. If errors are detected, the transmitter retransmits the data block.
  • Hybrid Automatic Repeat request (HARQ):

    • HARQ is a combination of FEC and ARQ, providing a hybrid approach to error management. It integrates the use of redundant information (FEC) with the ability to request retransmissions (ARQ). HARQ processes are classified into fast and slow processes. Fast HARQ allows for quick retransmissions within a short time window, while slow HARQ provides additional opportunities for recovery over a longer time period. HARQ processes in 4Goften include a technique called soft combining. In soft combining, the receiver combines information from multiple received copies of the same data block, even if they are received with errors. This improves the chances of correct reception and enhances overall system performance.

The choice of FEC, ARQ, and HARQ mechanisms depends on factors such as the nature of the data, latency requirements, and the characteristics of the wireless channel.

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