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<h3>Inter-System Direct Access</h3>

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<h4>Inter-System
Direct Access to the WCDMA RAN</h4>

<p>The purpose of the Inter-System Direct Access to the WCDMA
RAN is to enable the BSC to hand a mobile directly from the SDCCH channel
of a serving cell to the WCDMA RAN. Inter-System Direct Access is application
software that can be enabled by the parameter <span class="parameter-sem">Inter-System
Direct Access Enabled</span>. Idle state measurement parameters of the WCDMA
RAN neighbours are sent to the dual mode GSM/WCDMA mobiles in the System Information
Type 2quater messages. These parameters are also used on SDCCH channel for
the Inter-System Direct Access. The following conditions have to be fulfilled
before the handover attempt can be initiated by the BSC:</p>


<ul>
<li><p>Inter-System Handover has to be enabled.</p>
</li>
<li><p>Inter-System Direct Access has to be
enabled by the parameter <span class="parameter-sem">Inter-System Direct Access
Enabled</span>.</p>
</li>
<li><p>The BSC must have received an indication
from the mobile about its WCDMA RAN capability in the CLASSMARK_CHANGE message.
The mobile has to be FDD capable. The message must already have been received
on the SDCCH. </p>
</li>
<li><p>The mobile must have received information
about the adjacent WCDMA RAN cells from the BSC already on the SDCCH.</p>
</li>
<li><p>Traffic load of the serving GSM cell
exceeds the load threshold. The operator defines the load threshold by the
parameter <span class="parameter-sem">Inter-System Direct Access Load Threshold</span>
or by the parameter <span class="parameter-sem">Min Traffic Load For Speech Call</span>.
Decision of which load threshold the BSC uses for Inter-System Direct Access,
or is load checking used at all, is influenced by the service priority which
is sent by the MSC. </p>


<p>For more information about the service priority, see <a href="NED?action=retrieve&amp;identifier=dn03530043&amp;edition=3&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=dec831643157#dec831643157" onclick="sync(this);return true" shape="rect">Support of service priorities in A-interface</a>.</p>
</li>
<li><p>The BSC has to have received measurement
reports of the WCDMA RAN adjacent cell(s) already on the SDCCH.</p>
</li>
<li><p>The Ec/No of the target WCDMA RAN cell
has to be over the Inter-System Direct Access threshold direct access EC/IO
threshold.</p>
</li>
</ul>
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<h4>Unsuccessful
Inter-System Direct Access to the WCDMA RAN</h4>

<p>After an unsuccessful Inter-System Direct Access attempt,
the call is cleared.</p>
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