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<div class="div">
<h1>Dynamic Hotspot</h1>

<p>The Dynamic Hotspot is a feature designed to control traffic
in a frequency hopping radio network on the basis of interference and hence
to achieve higher radio network capacity.</p>


<p>The Dynamic Hotspot enables the usage of very tight frequency
reuse of hopping TRXs without quality degradation since the BSC can limit
traffic intensity in areas where interference tends to increase above an acceptable
level. Another advantage is that with unequal traffic distribution, some cells
can dynamically handle more traffic than others can when traffic intensity
in the other cells is relatively lower.</p>


<p>The BSC monitors the level of interference by means of
the measurement results reported by the MS/BTS. The degree of soft blocking
is fully controlled by means of adjustable parameters.</p>


<p>When the Dynamic Hotspot feature is employed by the BSC,
the radio resource management limits traffic intensity in areas where interference
tends to increase above an acceptable level. The radio resource management
limits traffic intensity by dynamically rejecting TCH requests in situations
of excessive interference although there might be free TCHs available (soft
blocking).</p>


<p>Soft blocking concerns traffic channel allocation from
RF hopping TRXs in a call, in an inter-cell handover, and in an underlay-overlay
handover. It is not applied in an intra-cell handover within a frequency group.
Traffic channels on BCCH TRXs are available at all times; that is, soft blocking
does not concern these channels. However, in base band frequency hopping the
BCCH TRX is treated as non- BCCH TRXs.</p>


<p>The soft blocking algorithm is based on the following criteria:</p>


<ul>
<li><p>Traffic intensity in a cell</p>
</li>
<li><p>Radio connection quality in the interfered
cells.</p>
</li>
</ul>


<p>The BSC begins to apply the soft blocking algorithm when
the number of busy TCHs in a BTS exceeds a predetermined threshold limit.
This threshold limit is controlled on a cell-by-cell basis. If the number
of busy TCHs in the BTS is lower than the threshold limit, radio resource
management may always allocate a TCH according to the requirements included
in the resource requests.</p>


<p>When the number of busy TCHs in the BTS exceeds the threshold
limit, radio resource management verifies the signal quality (percentage of
bad uplink/downlink quality) in those cells (interfered cells) that use the
same hopping frequencies (one or more) as the BTS and are close enough to
be interfered with. On the basis of this verification, radio resource management
calculates a probability, which is used to determine whether a TCH can be
allocated or not.</p>


<p>When the signal quality is good in every interfered cell,
the probability is 1. Thus, the radio resource management may allocate a TCH
from the BTS.</p>


<p>If the signal quality is below an acceptable level in a
single interfered cell, the radio resource management may not allocate a TCH,
that is, the probability is 0.</p>


<p>If signal quality is at least acceptable (=between good
and bad) in every interfered cell (but not good in all cells), an adjacent-cell-specific
probability of channel allocation is determined for each adjacent cell by
comparing the adjacent cell signal quality to the signal quality threshold
table. The threshold table is defined by the operator (see the example below).
The final probability is achieved by multiplying all adjacent-cell-specific
probabilities.</p>


<p>The probability is then compared with a fixed reference
value (50). The TCH request is accepted if the probability is greater than
the reference value.</p>


<a name="mar241230612" shape="rect"></a>
<div>
<h6>Example</h6>


A super-reuse TCH is requested from an RF hopping BTS.
The number of busy super-reuse TSLs exceeds the threshold  SoftblockingThresholdOnSuperReuseFrequency,
thus the soft blocking algorithm is activated. The BTS has two interfered
cells, A and B, which use the same hopping frequencies. The signal quality
in cell A is below BadQualLimit but above SigQualLimit1. The signal quality
in cell B is below SigQualLimit2 but above GoodQualLimit. The operator has
defined the probabilities of the TCH allocation according to the table below:</div>


<a name="mar241231513" shape="rect"></a>
<div>
<p>Table: Example of TCH allocation probabilities</p>


<table border="1">
<tbody>
<tr align="center" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1" valign="middle"><p>Signal Quality % Probability %</p>
</td>
<td colspan="1" rowspan="1" valign="middle"><p></p>


 </td>
<td colspan="1" rowspan="1" valign="middle"><p></p>


 </td>
</tr>
<tr align="center" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>&gt;= BadQualLimit0</p>


<p>&lt; BadQualLimit</p>


<p> &gt;= SigQualLimit1</p>


<p>(TCH Probability1)</p>
</td>
<td colspan="1" rowspan="1"><p>0</p>
</td>
<td colspan="1" rowspan="1"><p></p>


<p></p>


<p>51</p>
</td>
</tr>
<tr align="center" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>&lt; SigQualLimit1</p>


<p>&gt;= SigQualLimit2</p>


<p>(TCH Probability2)</p>
</td>
<td colspan="1" rowspan="1"><p></p>


 </td>
<td colspan="1" rowspan="1"><p></p>


<p>72</p>
</td>
</tr>
<tr align="center" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>&lt; SigQualLimit2 </p>


<p>&gt;= GooQualLimit </p>


<p>(TCH Probability3)</p>
</td>
<td colspan="1" rowspan="1"><p></p>


 </td>
<td colspan="1" rowspan="1"><p></p>


<p>80</p>
</td>
</tr>
<tr align="center" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>&lt; GoodQualLimit</p>
</td>
<td colspan="1" rowspan="1"><p></p>


 </td>
<td colspan="1" rowspan="1"><p>100</p>
</td>
</tr>
</tbody>
</table>
</div>


<p>The probability of allocating a TCH in this example is
40% (0.51*0.80 = 0.40). GoodQualLimit, BadQualLimit, SigQualLimit, and TCHPropability
are adjustable parameters.</p>
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