10.1 Introduction to Bursty Channels
The coding techniques introduced to this point have been appropriate for channels with independent random errors, such as a memoryless binary symmetric channel, or an AWGN channel. In such channels, each transmitted symbol is affected independently by the noise. We refer to the codes that are appropriate for such channels as random error correcting codes. However, in many channels of practical interest, the channel errors tend to be clustered together in “bursts.” For example, on a compact disc (CD), a scratch on the media may cause errors in several consecutive bits. On a magnetic medium such as a hard disk or a tape, a blemish on the magnetic surface may introduce many errors. A wireless channel may experience fading over several symbol times, or a stroke of lightning might affect multiple digits. In a concatenated coding scheme employing a convolutional code as the inner code, a single incorrect decoding decision might give rise to a burst of decoding errors.
Using a conventional random error‐correcting block code in a bursty channel leads to inefficiencies. A burst of errors may introduce several errors into a small number codewords, which therefore need strong correction capability, while the majority of codewords are not subjected to error and therefore waste error‐correction capabilities.
In this chapter, we introduce techniques for dealing with errors on bursty channels. ...