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<div class="div">
<h1>Dynamic Abis procedures</h1>

<p>In the DAP upgrade/downgrade procedure, the BSC downgrades all packet
switched traffic channels from the PCU and then upgrades these same traffic
channels to packet switched use again. This short interruption ensures optimised
PCU DSP resource usage for each DAP connected to the PCU.</p>


<a name="feb22313404914" shape="rect"></a>
<div class="topic">
<h2>Dynamic
Abis Pool upgrade</h2>

<p>The BSC performs the DAP upgrade procedure when:</p>


<ol class="type-odd">
<li type="1"><p>the DAP is created</p>
</li>
<li type="1"><p>new circuits are added to the DAP</p>
</li>
<li type="1"><p>the PCU controlling the DAP is restarted.</p>
</li>
</ol>


<p>There are two phases in the DAP upgrade procedure:</p>


<ol class="type-odd">
<li type="1"><p>In the first phase the BSC makes connections between Abis <a href="NED?action=retrieve&amp;identifier=general_glossary&amp;edition=13&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=id013463#id013463" onclick="openSmallPopup(event,'NED?action=retrieve&amp;identifier=general_glossary&amp;edition=13&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=id013463#id013463');return false" shape="rect" target="_blank">ETPCM</a> circuits and PCUPCM circuits. </p>
</li>
<li type="1"><p>In the second phase the BSC attaches DAP circuits to DAP by informing
the PCU about mappings between the Abis ETPCM circuits and the PCUPCM circuits.</p>
</li>
</ol>


<p>The BSC connects DAP circuits to DAP starting from the
last circuit and then connecting the next circuit from the side of previous
circuit as long as there are circuits configured to EGPRS use. DAP is always
comprised of consecutive DAP circuits. All the circuits belonging to the DAP
are connected to the DAP.</p>
</div>


<a name="feb22313414415" shape="rect"></a>
<div class="topic">
<h2>EGPRS
Dynamic Abis Pool downgrade</h2>

<p>The BSC starts the DAP downgrade procedure when:</p>


<ol class="type-odd">
<li type="1"><p>the DAP is deleted</p>
</li>
<li type="1"><p>circuits are removed from the DAP</p>
</li>
</ol>


<p>There are two phases in the DAP downgrade procedure: </p>


<ol class="type-odd">
<li type="1"><p>In the first phase the BSC detaches DAP circuits from the DAP
by informing the PCU about changed mappings between Abis ETPCM circuits and
PCUPCM circuits. </p>
</li>
<li type="1"><p>In the second phase the BSC releases connections between the
Abis ETPCM circuits and the PCUPCM circuits.</p>
</li>
</ol>
</div>


<a name="feb22313421116" shape="rect"></a>
<div class="topic">
<h2>BCSU
(PCU) restart</h2>

<p>When the BCSU is restarted the BSC releases all DAP connections
related to the BCSU. After the PCU becomes operational again, the BSC runs
an upgrade procedure for each DAP controlled by the PCU. The PCU shares the
DSP resources optimally for all the DAPs when the BCSU (PCU) is restarted.</p>
</div>


<a name="feb22313422817" shape="rect"></a>
<div class="topic">
<h2>BCSU
(PCU) switchover</h2>

<p>If a switchover is made for the BCSU, the BSC releases
all DAP connections related to the old BCSU and then starts an upgrade procedure
to recover the DAP connections in the new BCSU. The PCU shares the DSP resources
optimally for all the DAPs in BCSU (PCU) switchover.</p>
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