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<div class="div">
<h1>Directed Retry</h1>

<p>Directed Retry is a feature designed to improve the trunking
efficiency in case of temporary congestion.</p>


<p>In case of a call set-up (mobile originated or mobile terminated)
when congestion occurs in the serving cell, the MS can be handed over to the
traffic channel of an adjacent cell. The adjacent cell selection is based
on downlink signal level. If that exceeds the operator-defined threshold (as
per adjacent cell basis), the Directed Retry can be done.</p>


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<p>Table: Directed retry</p>


<table border="1">
<thead>
<tr align="left" char="" charoff="50" valign="bottom">
<th colspan="1" rowspan="1" valign="top"><p></p>


 </th>
<th colspan="1" rowspan="1" valign="top"><p>RxLevMin</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>RX Level</p>
</th>
</tr>
</thead>
<tbody>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p><span class="menupath-sem">Cell B</span></p>
</td>
<td colspan="1" rowspan="1"><p>-100 dBm</p>
</td>
<td colspan="1" rowspan="1"><p>-92 dBm</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p><span class="menupath-sem">Cell C</span></p>
</td>
<td colspan="1" rowspan="1"><p>-100 dBm</p>
</td>
<td colspan="1" rowspan="1"><p>-105 dBm</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p><span class="menupath-sem">Cell D</span></p>
</td>
<td colspan="1" rowspan="1"><p>-100 dBm</p>
</td>
<td colspan="1" rowspan="1"><p>-85 dBm</p>
</td>
</tr>
</tbody>
</table>
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<p>The operator can also define a separate, adjacent cell
specific, threshold for the signal level. This threshold value is used when
deciding if the adjacent cell is selected as a candidate cell in the directed
retry procedure or not.</p>


<p>The picture below presents the situation where the mobile
is camped in cell A but congestions occur. The MS measures also cells B, C,
and D. The downlink signal levels of cells B and D exceeds the operator defined
thresholds and so directed retry is possible to cells B and D but not to cell
C. The MS is tried to hand over to cell D because its downlink signal level
is higher than that of cell B. If congestion occurs also in cell D, the MS
is tried to hand over to cell B.</p>


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<img alt="urn:mars:dn0468839:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0468839&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Mobile is camped in cell A but congestions occur</p>
</div>


<p>A cell specific parameter defines the minimum time after
which the DR handover to another cell is started. During this delay, a call
set up is queuing for a TCH in the congested cell if queuing feature is in
use. Due to this delay, more measurements are available for the DR candidate
cell list evaluation.</p>
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