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<h1>12-TRX Cell with RTC Dual Duplexing</h1>

<p>New capacity features such as IUO and FH will give operators
more possibilities of using higher capacity configurations. The introduction
of dual band also sets requirements for increasing the number of TRXs in a
BTS.</p>


<p>At the moment, the maximum configuration for a Nokia Talk-family
BTS with RTC is 6+6 TRXs with one BTS and 6+6+6 TRXs with two BTSs. This is
due to the combiner solutions. In the current product architecture, the internal
dimensioning and design solutions have been done from the viewpoint that 12
is the maximum number of TRXs that will be supported under one BCF. By modifying
the combiner solution, it is possible to build high-capacity sites with up
to 12+12+12 TRXs by installing BTSs side by side.</p>


<p>The dual-duplex RTC solution increases the BTS capacity
up to 12 TRXs per cell. There are two different solutions available depending
on the number of antennas in use. The number of antennas can be minimised
by using two additional 3 dB splitters to divide the main and diversity receive
signals between the RTC duplex filter and RMU units. In this case, only two
antennas are needed. The use of splitters causes 3 dB degradation in RX sensitivity,
but this can be compensated by using MastHead Preamplifiers, if necessary.</p>


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<img alt="urn:mars:dn0468324:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0468324&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Two-antenna solution</p>
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<p>Alternatively, there is a four-antenna solution. By using
four antennas, 3 dB splitters are not needed at all, and therefore there is
no degradation in RX sensitivity. Two additional antennas are needed for the
diversity RX branches.</p>


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<img alt="urn:mars:dn0468254:1:en:global:cgm_fixed:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0468254&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Four-antenna solution</p>
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<p>If RTC got faulty in previous software releases, all TRX
faults in those TRXs, which were connected to faulty RTC, were recovered one
by one. This enabled unnecessary TRX recoveries. Now those faults are reported
in a list, which prevents unnecessary TRX recovery actions. It is also possible
to make a multiple TRX recovery if needed. For example if IUO is in use, it
might be necessary to swap also the SDCCH TRX and TCH TRXs, not only BCCH
TRX.</p>
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