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<div class="div">
<h1>Packet Control Unit (PCU) Hardware in BSC</h1>

<p>The Packet Control Unit (PCU) is a plug-in unit that controls
the (E)GPRS radio resources, receives, and transmits TRAU frames to the BTSs
and Frame Relay packets to the SGSN.</p>


<p>The PCU implements both the Gb interface and RLC/MAC protocols in the
BSS. It acts as the key unit in the following procedures:</p>


<ul>
<li><p>(E)GPRS radio resouce allocation and management</p>
</li>
<li><p>(E)GPRS radio connection establishment and management</p>
</li>
<li><p>data transfer</p>
</li>
<li><p>coding scheme selection</p>
</li>
<li><p>PCU statistics</p>
</li>
</ul>


<p>With the full PCU configuration, the operator can share
the BTS domain controlled by one BSC for multiple PCUs. One BTS is, however,
always controlled by one PCU. The operator needs to reserve the Gb interface
capacity from all PCUs, which are connected to BTSs, that is, from the active
PCUs.</p>


<p>One logical PCU can manage up to 256 Abis 16k-sub timeslots,
which are directly mapped to Air interface PDCH channels. The PCU removes
the unnecessary TRAU overheads coming from the Abis interface and assembles
the data into Frame Relay for the Gb interface. The BSC and SGSN are connected
to each other with one or more n*64kbit/s Gb interfaces. The number of interfaces
is equal to the number of PCUs, that is, each PCU has its own logical Gb interface.
Gb is a Frame Relay interface, and it can be configured in 64kbit/s steps
from 1 timeslot up to 31 timeslots depending on the capacity requirements. </p>


<p>PCU is a general term for all Nokia GSM/EDGE PCU versions. The Nokia
GSM/EDGE PCU product family is shown in the table below.</p>


<a name="dec28415592720" shape="rect"></a>
<div>
<p>Table: The Nokia GSM/EDGE PCU product family</p>


<table border="1">
<thead>
<tr align="left" char="" charoff="50" valign="bottom">
<th colspan="1" rowspan="1" valign="top"><p>General name</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>Name of HW product variant</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>Explanation</p>
</th>
</tr>
</thead>
<tbody>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="2"><p>Nokia First Generation Packet Control Unit - PCU1</p>
</td>
<td colspan="1" rowspan="1"><p>PCU</p>


<p>PCU-S</p>


<p>PCU-T</p>
</td>
<td colspan="1" rowspan="1"><p>First generation PCU for BSCE, BSC2E/A, BSCi and BSC2i</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>PCU-B</p>
</td>
<td colspan="1" rowspan="1"><p>First generation PCU for BSC3i, includes two logical PCUs</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="2"><p>Nokia Second Generation Packet Control Unit - PCU2</p>
</td>
<td colspan="1" rowspan="1"><p>PCU2-U</p>
</td>
<td colspan="1" rowspan="1"><p>Second generation PCU for BSCE, BSC2E/A, BSCi and BSC2i</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>PCU2-D</p>
</td>
<td colspan="1" rowspan="1"><p>Second generation PCU for BSC3i, includes two logical PCUs</p>
</td>
</tr>
</tbody>
</table>
</div>


<a name="dec28416462122" shape="rect"></a>
<div class="topic">
<h2>PCU capacity and connections</h2>

<p>The PCU connections are implemented, as follows:</p>


<ul>
<li><p>In case of Frame Relay, two 2 Mbit/s PCM lines are connected
through the GSWB to the Abis interface, and one 2 Mbit/s line to the Gb interface
towards the SGSN.</p>
</li>
<li><p> In case of UDP/IP, there is a 100 Mbit/s Ethernet interface
towards the SGSN.</p>
</li>
</ul>


<p>One PCU can handle the GPRS traffic of 256 radio time slots. The maximum
number of connected traffic channels (16kbit/s) in GPRS use in a BSS is: </p>


<ul>
<li><p>2048 (that is, 8 times 256) for BSCE and BSCi</p>
</li>
<li><p>4096 (16 times 256) for BSC2A, BSC2E and BSC2i</p>
</li>
<li><p>6144 (24 times 256) for BSC3i.</p>
</li>
</ul>


<p>Furthermore, one PCU can handle a maximum of 64 cells/segments. One
PCU1 can handle a maximum of 64 BTSs and 128 TRXs. One PCU2 can handle a maximum
of 128 BTSs and 256 TRXs.</p>


<p>There is a configuration available for BSC2E/A and BSC2i,
where it is possible to add a second PCU (PCU-S or PCU-T) per each BCSU unit
(8+1) to further increase the packet processing capacity. The implementation
of a second PCU also requires a GSWB extension from 192 to 256 PCMs. Correspondingly,
the BSCs external connectivity and PCMs can be extended from 112 to 144 external
PCMs in BSC2s with 2*ET5C extra cartridges.</p>
</div>


<a name="apr1541953574" shape="rect"></a>
<div>
<img alt="urn:mars:dn0469611:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0469611&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: BSC2i EGPRS HW Extension options</p>
</div>


<a name="dec2841726391" shape="rect"></a>
<div class="topic">
<h2>PCU characteristics</h2>

<ul>
<li><p>Radio network connectivity:</p>


<ul>
<li><p>PCU1: 128 TRXs, 64 cells/segments, 64 BTSs</p>
</li>
<li><p>PCU2: 256 TRXs, 64 cells/segments, 128 BTSs</p>
</li>
</ul>
</li>
<li><p>Channel connectivity:</p>


<ul>
<li><p>The maximum number of 16 kbit/s channels per logical PCU (PCU1
or PCU2) is 256.</p>
</li>
<li><p>For PCU and PCU-S the supported number of RTSLs (for GPRS and
EGPRS channels) is 128, the full connectivity of 256 channels can be reached
with EDAP channels.</p>
</li>
<li><p>PCU1 has 16 DSP cores per one logical PCU1. One DSP core can
handle one EGPRS Dynamic Abis Pool (EDAP), but one EDAP can be shared by several
DSP cores.</p>


<p>One DSP core can handle up to 20 (16 kbit/s) channels, including EDAP
channels, EGPRS channels, GPRS channels and PBCCH/PCCCHs.</p>
</li>
<li><p>PCU2 has 8 DSP cores per one logical PCU2. One DSP core can handle
two EGPRS dynamic Abis pool (EDAP), but one EDAP can be shared by several
DSP cores.One DSP core can handle 0 to 40 channels (16 kbit/s), including
active EDAP channels, EGPRS channels, GPRS channels, and PBCCH/PCCCHs.</p>
</li>
</ul>
</li>
</ul>
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