Chapter 9. Error Correction

• Forward Error Correction

• Channel Coding

• Retransmission

• Implementation Considerations

Although it is clearly important to be able to conceal the effects of transmission errors, it is better if those errors can be avoided or corrected. This chapter presents techniques that the sender can use to help receivers recover from packet loss and other transmission errors.

The techniques used to correct transmission errors fall into two basic categories: forward error correction and retransmission. ⁸⁰ Forward error correction relies on additional data added by the sender to a media stream, which receivers can then use to correct errors with a certain probability. Retransmission, on the other hand, relies on explicit requests for additional copies of particular packets.

The choice between retransmission and forward error correction depends on the application and on the network characteristics. The details and trade-offs of the different approaches are discussed in more detail in this chapter.