<?xml version="1.0" encoding="utf-8" standalone="yes"?><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Incremental Redundancy (IR)</title>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<meta content="text/css" http-equiv="Content-Style-Type" />
<script src="NED?action=retrieve&amp;identifier=dn00188761&amp;edition=1&amp;language=none&amp;coverage=global&amp;encoding=javascript&amp;component=data&amp;item=data" type="text/javascript" xml:space="preserve">
</script>
<?conversion name="Pub2XHTML" version="2.0" source="urn:mars:dn02242744:3:en:global:publishing_online_1_0:data:data:*:*:*" date="2005-02-28T15:52:17Z"?>
<link href="NED?action=retrieve&amp;identifier=dn01158124&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=css&amp;component=data&amp;item=data" rel="stylesheet" title="Nokia Networks default online style" type="text/css" />
<meta content="draft" name="status" />
<?conversion name="SplitHTML" version="1.9" source="urn:mars:dn02242744:3:en:global:publishing_online_1_0:data:data:71:*:*" date="2005-02-28T15:52:17Z"?>
</head>
<body lang="en" xml:lang="en">
<p><a name="ned_top" shape="rect"></a>
<a name="ned_1" shape="rect"></a></p>

<a name="nov25291171" shape="rect"></a>
<a name="p2xhtm-repid-1" shape="rect"></a>
<table width="100%">
<tr>
<td align="center" colspan="1" rowspan="1" width="20%"><?NED5 annotation?>
<br clear="none" /><?NED5 printview?>
</td>
<td align="center" colspan="1" rowspan="1" width="20%"></td>
<td align="center" colspan="1" rowspan="1" width="20%"></td>
<td align="center" colspan="1" rowspan="1" width="20%"></td>
<td align="center" colspan="1" rowspan="1" width="20%"><a href="NED?action=retrieve&amp;identifier=dn02242744_about&amp;edition=3&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=ned_top#ned_top" onclick="openSmallPopup(event,'NED?action=retrieve&amp;identifier=dn02242744_about&amp;edition=3&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=ned_top#ned_top');return false" shape="rect" target="_blank"><img alt="Document information" border="0" class="Metainfo" src="NED?action=retrieve&amp;identifier=dn01158003&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /></a></td>
</tr>
</table>


<div class="div">
<h1>Incremental Redundancy (IR)</h1>

<p>Incremental Redundancy (IR) is an efficient combination
of two techniques: </p>


<ul>
<li><p>Automatic Repeat reQuest (<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=id011276#id011276" 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=id011276#id011276');return false" shape="rect" target="_blank">ARQ</a>)</p>
</li>
<li><p>Forward Error Correction (<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=id09440#id09440" 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=id09440#id09440');return false" shape="rect" target="_blank">FEC</a>).</p>
</li>
</ul>


<p>The ARQ method means that if the receiver detects the presence of errors
in a received <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> block, it requests and receives
a re-transmission of the same RLC block from the transmitter. The process
continues until an uncorrupted copy reaches the destination.</p>


<p>The FEC method adds redundant information to the re-transmitted information
at the transmitter, and the receiver uses the information to correct errors
caused by disturbances in the radio channel.</p>


<p>IR needs no information about link quality to in order
to protect the transmitted data. Thus, the benefits of IR include increased
throughput due to automatic adaptation to varying channel conditions, and
reduced sensitivity to link quality measurements.</p>


<a name="oct64111921" shape="rect"></a>
<div class="topic">
<h2>Incremental Redundancy scheme</h2>

<p>In the IR scheme (also known as Type II Hybrid ARQ scheme)
is implemented using the nine EGPRS <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=id09745#id09745" 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=id09745#id09745');return false" shape="rect" target="_blank">MCS</a>s. Only a
small amount of redundancy is sent first, which yields a high user throughput
if the decoding is successful. However, if the decoding fails, a re-transmission
takes place according to the ARQ method and the transmitter transmits a different
set of FEC information from the same RLC block. These sets are called protection
schemes. There can be either two (P1 and P2) or three (P1, P2 and P3) protection
schemes in each of the nine MCSs.</p>


<p>A data block is first protected with the P1 of a certain MCS. If the
decoding fails, the received P1 is stored in the receiver's memory for future
use and data block is re-transmitted using the P2 of the same MCS. If after
P3 the data still cannot be recovered, P1 is sent again and combined with
the stored P1, P2, and P3 schemes (reaching a protection level of about four
times P1), and so on, until the data is recovered.</p>


<p>The IR scheme is illustrated in the figure <em>Incremental
Redundancy scheme</em>. Since the combination includes more information
than any individual transmission, the probability of correct reception is
increased. IR co-operates with Link Adaptation (LA) that selects the amount
of redundant information transmitted in each transmission.</p>


<a name="nov2821559571" shape="rect"></a>
<div>
<img alt="urn:mars:dn02242117:1:en:global:cgm_fixed:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn02242117&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Incremental Redundancy scheme</p>
</div>
</div>


<a name="dec52915101" shape="rect"></a>
<div class="topic">
<h2>Related
topics</h2>

<p><a href="NED?action=retrieve&amp;identifier=dn02242662&amp;edition=5&amp;language=en&amp;coverage=global&amp;encoding=xhtml_1_0&amp;component=data&amp;item=data&amp;pointer=nov22215133515#nov22215133515" onclick="sync(this);return true" shape="rect">Overview of Nokia EDGE</a></p>
</div>
</div>
</body>
</html>