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<h1>Bad Frame Handling Improvement (Poor field improvement)</h1>

<p>This feature improves the quality of the speech by handling
better the situation where a lot of bad speech frames are received.</p>


<p>In Recommendation 06.31, it is stated that: ‘Whenever a
good speech frame is detected, the DTX handler shall pass it directly on to
the speech decoder’. This is, however, not a very good solution, for example,
when the mobile is in a weak radio field and individual good speech frames
are surrounded with bad frames. In this case, these good speech frames cause
only some arbitrary sounds as they do not contain enough information so that
they could be interpreted as speech. It is also more probable that error detection
and correction methods have failed, and the frame that has been interpreted
as good is actually bad.</p>


<p>An improved bad frame handling method is used to prevent
short unpleasant sounds. This method works in the uplink direction, and it
mutes the signal smoothly if there is evidence of errors, and it also demutes
smoothly once good frames are received again.</p>
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