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Unformatted text preview: the odds of being in a “good” state
are high if the previous few bits have been correct.
At ﬁrst sight, it might seem like the SEC schemes we studied are poorly suited for a
channel experiencing burst errors. The reason is shown in Figure 6-8 (left), where each
block of the message is protected by its SEC parity bits. The different blocks are shown as
different rows. When a burst error occurs, multiple bits in an SEC block are corrupted, and
the SEC can’t recover from them.
Interleaving is a commonly used technique to recover from burst errors on a channel
even when the individual blocks are protected with a code that, on the face of it, is not
suited for burst errors. The idea is simple: code the blocks as before, but transmit them in
a “columnar” fashion, as shown in Figure 6-8 (right). That is, send the ﬁrst bit of block 1,
then the ﬁrst bit of block 2, and so on until all the ﬁrst bits of each block are sent. Then,
send the second bits of each block in sequence, then the third bits, and so on.
What happens on a burst error? Chances are that it corrupts a...
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- Fall '13