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  • NAT Traversal Service
  • No : 2021
  • 公開日時 : 2013/04/10 15:00
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What is automatic rate control, forward error correction (FEC), automatic repeat request (ARQ), and decoder error hiding? Please give a simple explanation.

Answer

Automatic rate control adjusts the data volume transmitted to the level of network congestion.
Forward error correction is a system that adds redundancy to the transmitted data to allow the receiver to detect and correct errors without having to ask the sender for additional data. (Error correction by time-consuming resending is not suitable for transmitting moving pictures, which requires real-time performance.)
Automatic repeat request is a system that notifies the sender when the network was unable to transmit data correctly and then retransmits only the unsent data. Because only the unsent data is retransmitted, the data volume transmitted over the network can be kept lower. (However, this system is not suitable for applications with a large network delay, because it takes time to request retransmission and retransmit the unsent data.)
Demarcation between forward error correction and automatic repeat request — Forward error correction is used for networks with a large network delay, and automatic repeat request is used for networks with a small network delay because of its smaller volume of redundant data (required data other than video and audio). Rather than choosing between the two methods, they are both properly balanced and used in response to the network delay.
Decoder error hiding refers to subjectively and discreetly modifying data packets where network transmission errors occurred that cannot be corrected by FEC or ARQ.

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