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<div class="div">
<h1>Overview of Dynamic Frequency and Channel Allocation (DFCA)</h1>

<p>Dynamic Frequency and Channel Allocation (DFCA) is a powerful
software product designed to provide maximum capacity from scarce frequency
resources. It is a channel assignment method for dynamically assigning the
optimum radio channel for a new circuit-switched call, <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=id08638#id08638" 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=id08638#id08638');return false" shape="rect" target="_blank">directed retry</a>, or incoming handover. DFCA is
based on real-time knowledge of frequency usage and interference at any given
location in the network.</p>


<p>Different interference tolerance properties of different connection
(codec) types are taken into account in the channel selection process. Thus
a channel with a lower <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=id013651#id013651" 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=id013651#id013651');return false" shape="rect" target="_blank">C/I</a>
(carrier-to-interference) ratio can be assigned for better codecs like AMR,
saving capacity for less robust codecs that require channels with higher C/I.</p>


<p>By dynamically allocating frequency hopping parameters (<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=id05751#id05751" 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=id05751#id05751');return false" shape="rect" target="_blank">MA</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=id011241#id011241" 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=id011241#id011241');return false" shape="rect" target="_blank">MAIO</a>)
for each individual timeslot, DFCA provides more effective frequency reuse
than a static frequency plan. This leads to a significant capacity gain with
ensured quality.</p>


<p>DFCA is an application software product and requires a valid licence
in the BSC.</p>


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<h2>Principle</h2>

<p>DFCA uses interference estimations derived from mobile station downlink
measurement reports and combines them with the timeslot and frequency usage
information. The DFCA algorithm selects a frequency hopping radio channel
for a connection, based on the C/I ratio criteria. Both the C/I for the new
connection and the interference effect on existing connections are estimated
before channel allocation. DFCA channel allocation ensures enough quality
in terms of C/I so that each connection will meet its <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=id08604#id08604" 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=id08604#id08604');return false" shape="rect" target="_blank">Quality of Service</a> (QoS) requirements.</p>


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<img alt="urn:mars:dn058274:1:en:global:cgm_fixed:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn058274&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Principle of DFCA</p>
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<h2>Architecture and main concepts</h2>

<ul>
<li><p><em>BSS synchronisation</em></p>


<p>To estimate interference on a timeslot basis, DFCA needs to know how
connections in different cell sites interfere with each other. This is only
achieved in a BSS synchronised network.</p>


<p>Nokia's BSS Synchronisation has been designed to align timeslot transmission
between cell sites in the air interface. When BTSs are synchronised to a global
clock source, transmission of TDMA frames will take place precisely at a known
and controlled moment. This is implemented by a synchronisation unit, the
Location Measurement Unit (LMU), installed at every base station site. The
LMU receives the GPS signal and feeds the BTSs with a consistent TDMA frame
clock.</p>


<p>For more information, see <a href="NED?action=retrieve&amp;identifier=dn04122203&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=dec331522341#dec331522341" onclick="sync(this);return true" shape="rect">BSS
Synchronisation</a>.</p>
</li>
<li><p><em>Inter-BSC connection</em></p>


<p>Since the DFCA algorithm estimates interference coming from or caused
to existing connections, information about the channel usage in surrounding
BSCs must be available. Otherwise DFCA would be limited only to the inner
cells of a BSC area. The BSC-BSC Interface (BBI) is used to exchange channel
reservation and measurement information between neighbouring BSCs. In BBI,
each pair of neighbouring BSCs is connected to each other. BBI is an <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=id01203#id01203" 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=id01203#id01203');return false" shape="rect" target="_blank">SCCP</a> over IP connection terminated at the LAN
connectors of BCSUs.</p>


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<img alt="urn:mars:dn056182:1:en:global:cgm_fixed:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn056182&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: DFCA system architecture</p>
</div>
</li>
<li><p><em>DFCA hopping and cell configuration</em></p>


<p>DFCA uses the DFCA frequency hopping mode that allows full freedom on
radio channel selection on the timeslot level (MA, MAIO, TSC). DFCA hopping
is cyclic RF hopping.</p>


<p>The used frequency band must be divided into two: frequencies for the
regular layer (BCCH and packet data) and frequencies for the DFCA layer. DFCA
frequencies are arranged to one or more DFCA MA lists that are the same in
all BSCs over the whole DFCA network.</p>
</li>
</ul>
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<h2>Benefits of the Nokia solution </h2>

<ul>
<li><p>Increased capacity through higher effective frequency load</p>


<p>DFCA allows for more circuit-switched traffic by adding more TRXs to
the existing BTSs without compromising the quality. Alternatively, more frequencies
are released from the DFCA layer to the regular layer, thus increasing the
performance and capacity of (E)GPRS.</p>
</li>
<li><p>Enhanced quality through C/I optimisation</p>


<p>Network performance is significantly improved in terms of received signal
quality (RXQUAL), frame error rate (FER), and the dropped call rate.</p>
</li>
<li><p>Enhanced Quality of Service control</p>


<p>Different circuit-switched traffic call classes, such as EFR, HR, 14.4kbit/s
data, AMR FR, and AMR HR, can tolerate different interference conditions.
DFCA takes the C/I requirements of each connection into account and allocates
a suitable radio channel for it.</p>
</li>
</ul>
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<h2>Related topics</h2>

<ul>
<li><p><a href="NED?action=retrieve&amp;identifier=dn04103413&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=jun84175301#jun84175301" onclick="sync(this);return true" shape="rect">System impact of Dynamic
Frequency and Channel Allocation (DFCA)</a></p>
</li>
<li><p><a href="NED?action=retrieve&amp;identifier=dn04177859&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=sep24417433132#sep24417433132" onclick="sync(this);return true" shape="rect">Functionality of Dynamic
Frequency and Channel Allocation (DFCA)</a></p>
</li>
<li><p><a href="NED?action=retrieve&amp;identifier=dn04111335&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=jan751640542#jan751640542" onclick="sync(this);return true" shape="rect">Planning
Dynamic Frequency and Channel Allocation (DFCA)</a></p>
</li>
<li><p><a href="NED?action=retrieve&amp;identifier=dn04111347&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=sep244160569#sep244160569" onclick="sync(this);return true" shape="rect">Overview of implementing
Dynamic Frequency and Channel Allocation (DFCA)</a></p>
</li>
<li><p>For a detailed description of DFCA, see <em>Dynamic Frequency
and Channel Allocation in BSC</em> in BSC/TCSM documentation</p>
</li>
</ul>
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