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<h2>RLC/MAC and throughput optimisation for EGPRS</h2>

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<h3>RLC
ACK mode</h3>

<p><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=id08942#id08942" 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=id08942#id08942');return false" shape="rect" target="_blank">RLC</a> acknowledged operation mode is
required with TCP data transfer.</p>
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<h3>EGPRS
Packet Channel Request</h3>

<p>The one phase access reduces access procedure by half a
second, thus it is recommended that an EDGE cell support <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=id08928#id08928" 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=id08928#id08928');return false" shape="rect" target="_blank">PCCCH</a>
is used because the S10.5 BSS implementation does not support the EGPRS Packet
Channel Request message on <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=id04450#id04450" 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=id04450#id04450');return false" shape="rect" target="_blank">CCCH</a>. As a result, an EGPRS mobile
has to perform a 2-phase access on CCCH in order to request an uplink <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=id011257#id011257" 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=id011257#id011257');return false" shape="rect" target="_blank">TBF</a> in EGPRS mode. This causes extra delays when
compared with the PCCCH case.</p>


<p>EGPRS Packet Channel Request is supported on CCCH from
BSS11 onwards.</p>
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<h3>Delayed
TBF release</h3>

<p>The delayed TBF release in PCU takes TCP properties and <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=id013460#id013460" 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=id013460#id013460');return false" shape="rect" target="_blank">RTT</a> into account.</p>
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<h3>BS_CV_MAX</h3>

<p>The BS_CV_MAX parameter should define the RLC round-trip
delay in block periods.</p>


<p>If the BS_CV_MAX parameter is lower than the actual round-trip
delay or if the mobile is not able to do accurate time stamping for the uplink
(UL) RLC blocks, the mobile may transmit needless retransmissions after processing
a Packet UL ACK/NACK message.</p>


<p>If the BS_CV_MAX parameter has too high a value, or if
the mobile is not able to do accurate time stamping for the UL RLC blocks,
the mobile may ignore some negative acknowledgements that were received in
the Packet UL ACK/NACK message. This may distort the ARQ procedure slightly.</p>


<p>It is recommended to tune the BS_CV_MAX parameter so that
the minimum value is searched with which the mobile does not send needless
RLC retransmissions directly after the processing of a Packet UL ACK/NACK
message.</p>
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<h3>LA
parameters MAX BLER and Initial MCS</h3>

<p>The effect of MAX BLER is not crucial for TCP bulk transfer,
but likely improves performance of <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=id06081#id06081" 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=id06081#id06081');return false" shape="rect" target="_blank">UDP</a> streaming.
Effect of Initial MCS is likely not crucial for TCP.</p>
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<h3>Polling
period</h3>

<p>The default polling parameter values have been optimised
for TCP data transfer.</p>
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