## Interleaving

The block codes described thus far work best when errors are distributed evenly and randomly between incoming blocks. This is usually the case for channels corrupted primarily by AWGN, such as a land-line telephone link.
In a mobile radio environment, however, errors often occur in bursts as the received signal fades in and out due to the multipath propagation and the user's motion. In order to distribute these errors more evenly between coded blocks, a process known as interleaving is used.

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