The
purpose of interleaving is to randomize (or distribute) the bursty errors caused by the multipath channel
(or any other channel with memory, as well as Spectral Conversion (RF) impairments). This is
best described with the help of Fig. 5.2.
Prior to discussing the benefits of interleaving we would like to present its disadvantage.1 These
operations introduce time delays into the system. This time delay is the actual time required to perform
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1 This is contrary to the effective presentation principles, where the benefits are discussed first.
the interleaving plus the time required to perform de-interleaving. This increase in time delay can be
detrimental especially in a voice application.
Interleaving improves the performance of a communication system. It is a form of time diversity
that is used to mitigate the effects of bursty errors. A bit stream is considered to be ideally interleaved
when consecutive received bits are independent, in other words, not affected by the same burst of
errors. This is accomplished when adjacent bits of the transmitter are separated by more than the
AFTD of the channel. Similarly, a bit stream is considered to be partially interleaved when consecutive
received bits are affected by the same burst of errors.
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