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<h2>Support of service priorities in A-interface</h2>

<p>The BSC can receive service priority indication in the
ASSIGNMENT_REQUEST and in the HANDOVER_REQUEST messages. The indication informs
the BSC whether the connection in question:</p>


<ul>
<li><p>should be direct accessed or handed
over to the WCDMA RAN. WCDMA RAN is preferred. That is, the Handover Algorithm
should initiate inter-system direct access or inter-system handover to the
WCDMA RAN. Load thresholds <span class="parameter-sem">Inter-System Direct Access
Load Threshold</span> and <span class="parameter-sem">Min Traffic Load For Speech
Call</span> are ignored.</p>
</li>
<li><p>should not be direct accessed or handed
over to the WCDMA RAN. Neither inter-system direct access nor inter-system
handover to the WCDMA RAN should be performed. The BSC is not allowed to initiate
inter-system direct access from the GSM to the WCDMA RAN regardless of the
serving GSM cell load and load thresholds. Inter-system handover to the WCDMA
RAN is allowed only if the load of the serving GSM cell is over the threshold <span class="parameter-sem">Min Traffic Load For Speech Call</span>.</p>
</li>
<li><p>shall not be direct accessed, or handed
over to the WCDMA RAN. The GSM is preferred and WCDMA RAN is forbidden. That
is, the BSC is not allowed to initiate inter-system direct access or inter-system
handover from the GSM to the WCDMA RAN regardless of the serving GSM cell
load and load thresholds.</p>
</li>
<li><p>is not in use, if GSM-WCDMA Inter-System
Handover is activated in the BSC, but the BSC does not receive the service
priority indication, because the MSC does not support of sending it. The BSC
behaves like the service priority is not in use. Also if the BSC receives
service priority indicating something other than ‘should’, ‘should not’ or
‘shall not’, the BSC behaves like the service priority is not in use. When
the service priority is 'not in use' in the BSC, the inter-system direct access
to the WCDMA RAN is not allowed. Inter-system handover to the WCDMA RAN is
allowed only if the load of the serving GSM cell is over the threshold <span class="parameter-sem">Min Traffic Load For Speech Call</span>.</p>
</li>
<li><p>If GSM-WCDMA Inter-System Handover
is not activated, the BSC sets service priority as ‘disabled’.</p>
</li>
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