L6_2

# Probability is pg and in the bad state it is pb pb pg

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Unformatted text preview: empirical data exist, but we won’t go into them here. Our goal is to understand how to develop error correction mechanisms when errors occur in bursts. But what do we mean by a “burst”? The simplest model is to model the channel as having two states, a “good” state and a “bad” state. In the “good” state, the bit error 16 LECTURE 6. COPING WITH BIT ERRORS Figure 6-8: Interleaving can help recover from burst errors: code each block row-wise with an SEC, but transmit them in interleaved fashion in columnar order. As long as a set of burst errors corrupts some set of kth bits, the receiver can recover from all the errors in the burst. probability is pg and in the “bad” state, it is pb ; pb &gt; pg . Once in the good state, the channel has some probability of remaining there (generally &gt; 1/2) and some probability of moving into the “bad” state, and vice versa. It should be easy to see that this simple model has the property that the probability of a bit error depends on whether the previous bit (or previous few bits) are in error or not. The reason is that...
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