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<h2>WCDMA-GSM cell selection and re-selection</h2>

<p>After a <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=id011489#id011489" 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=id011489#id011489');return false" shape="rect" target="_blank">UE</a> has been switched on and a <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=id03765#id03765" 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=id03765#id03765');return false" shape="rect" target="_blank">PLMN</a>
has been selected, the cell selection process takes place. This process allows
the UE to select a suitable cell where it can camp in order to access available
services. In 'Stored information cell selection', the UE uses stored information.
In 'Initial cell selection', the UE does not use stored information. A suitable
cell is selected when the cell selection criterion S is fulfilled:</p>


<ul>
<li><p>Srxlev &gt; 0 AND Squal &gt; 0</p>
</li>
</ul>


<p>where:</p>


<ul>
<li><p>Squal = Q<sub>qualmeas</sub> – Qqualmin</p>
</li>
<li><p>Srxlev = Q<sub>rxlevmeas</sub> – Qrxlevmin
- Pcompensation</p>
</li>
</ul>


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<td colspan="1" rowspan="1"><p>Squal</p>
</td>
<td colspan="1" rowspan="1"><p>Cell Selection quality value (dB). Applicable only for
FDD cells.</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Srxlev</p>
</td>
<td colspan="1" rowspan="1"><p>Cell Selection RX level value (dB)</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Q<sub>qualmeas</sub></p>
</td>
<td colspan="1" rowspan="1"><p>Measured cell quality value. The quality of the received
signal expressed in CPICH Ec/N0 (dB) for FDD cells. Applicable only for FDD
cells.</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Q<sub>rxlevmeas</sub></p>
</td>
<td colspan="1" rowspan="1"><p>Measured cell RX level value. This is a received signal,
CPICH RSCP for FDD cells (dBm) and P-CCPCH RSCP for TDD cells (dBm).</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Qqualmin</p>
</td>
<td colspan="1" rowspan="1"><p>Minimum required quality level in the cell (dB). Applicable
only for FDD cells.</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Qrxlevmin</p>
</td>
<td colspan="1" rowspan="1"><p>Minimum required RX level in the cell (dBm)</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>Pcompensation</p>
</td>
<td colspan="1" rowspan="1"><p>max(UE_TXPWR_MAX_RACH – P_MAX, 0) (dB)</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>UE_TXPWR_MAX_RACH</p>
</td>
<td colspan="1" rowspan="1"><p>Maximum TX power level a UE may use when accessing the
cell on RACH (read in system information) (dBm)</p>
</td>
</tr>
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<td colspan="1" rowspan="1"><p>P_MAX</p>
</td>
<td colspan="1" rowspan="1"><p>Maximum RF output power of the UE (dBm)</p>
</td>
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<h3>Cell
re-selection</h3>

<p>The following parameters are compared with Squal (CPICH
Ec/No) for FDD cells and Srxlev (P-CCPCH RSCP) for TDD cells in S-Criteria: </p>


<ul>
<li><p><span class="parameter-sem">Sintrasearch</span></p>
</li>
<li><p><span class="parameter-sem">Sintersearch</span></p>
</li>
<li><p><span class="parameter-sem">SsearchRAT</span></p>
</li>
</ul>


<p>Then the cells are ranked according to the R-criteria.
The UE selects the best ranked cell (the cell with the highest R value). The
cell ranking criterion R is defined by:</p>


<ul>
<li><p>Rs = Q<sub>meas,s</sub> + Qhyst<sub>s</sub></p>
</li>
<li><p>Rn = Q<sub>meas,n</sub> - Qoffset<sub>s,n</sub></p>
</li>
</ul>


<p>where:</p>


<p>Qmeas is the quality value of the received signal based
on CPICH Ec/No or CPICH RSCP for FDD cells, P-CCPCH RSCP for TDD cells and
RxLev for GSM cells.</p>


<p>An example of the measurement rules of cell re-selection
for FDD cells (Squal is used) is illustrated as follows:</p>


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<img alt="urn:mars:dn02243085:1:en:global:cgm_fixed:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn02243085&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Measurement rules of cell re-selection when HCS is not used</p>
</div>


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<th colspan="1" rowspan="1" valign="top"><p>Region</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>Condition</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>Neighbour cells to be measured</p>
</th>
</tr>
</thead>
<tbody>
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<td colspan="1" rowspan="1"><p>1</p>
</td>
<td colspan="1" rowspan="1"><p>Squal &gt; S<sub>intrasearch</sub></p>
</td>
<td colspan="1" rowspan="1"><p>None</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>2</p>
</td>
<td colspan="1" rowspan="1"><p>S<sub>intersearch</sub> &lt; Squal ≤ S<sub>intrasearch</sub></p>
</td>
<td colspan="1" rowspan="1"><p>Intra-frequency cells</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>3</p>
</td>
<td colspan="1" rowspan="1"><p>Ssearch<sub>RAT</sub> &lt; Squal ≤ S<sub>intersearch</sub></p>
</td>
<td colspan="1" rowspan="1"><p>Intra- and inter-frequency cells</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>4</p>
</td>
<td colspan="1" rowspan="1"><p>Squal ≤ Ssearch<sub>RAT</sub></p>
</td>
<td colspan="1" rowspan="1"><p>Intra-, inter-frequency and inter-system cells</p>
</td>
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<p><a href="NED?action=retrieve&amp;identifier=dn02210994&amp;edition=5&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=nov1521223413#nov1521223413" onclick="sync(this);return true" shape="rect">Overview of GSM-WCDMA Inter-System Handover</a></p>
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