<?xml version="1.0" encoding="utf-8" standalone="yes"?><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Enhanced Full Rate Codec (ETSI)</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:dn0449713:1:en:global:publishing_online_1_0:data:data:*:*:*" date="2005-02-28T15:58:58Z"?>
<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:dn0449713:1:en:global:publishing_online_1_0:data:data:34:*:*" date="2005-02-28T15:58:58Z"?>
</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="jan18514285050" 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=dn0449713_about&amp;edition=1&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=dn0449713_about&amp;edition=1&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>Enhanced Full Rate Codec (ETSI)</h1>

<p>EFR is a new speech coding algorithm giving a better speech
quality than the current full rate (FR) coding. Tests indicate that better
quality or comparable to ADPCM could be offered with this codec. This feature
uses the state-of-the-art FR traffic channel basis at the speech rate of 13
kbit/s. The major difference between EFR and FR is the speech coding algorithm
itself. EFR does not require nor imply support for HR and vice versa.</p>


<p>The support for EFR at the BSS can be obtained for a network
as any normal SW update. At the A interface, the new TCSM2 equipment, if not
already in use, can be introduced gradually according to needs.</p>


<a name="mar1841224491" shape="rect"></a>
<div class="topic">
<h2>BTS</h2>

<p>The Base Transceiver Station (BTS) SW could be upgraded
to support Enhanced full rate speech coding. There is no need for HW upgrades
in any generation, which means that the support for EFR is always BTS-specific.
The SW upgraded BTSs are capable of supporting Full Rate and Enhanced full
rate coding dynamically. Each Radio Timeslot (RTSL) configured to support
a FR channel rate can be activated either as a FR or as an EFR Traffic Channel
(TCH) on a call.</p>
</div>


<a name="mar1841225332" shape="rect"></a>
<div class="topic">
<h2>BSC</h2>

<p>EFR could be used even if HR is not in use in the appropriate
network. Unlike with HR, only a software update is needed in any existing
BSC. Handovers between FR and EFR (and vice-versa) are possible when needed.
The Nokia GSM system has  plenty of parameters in the BSS, which have a direct
or indirect impact on the speech quality, and the optimisation and fine-tuning
of these can be carried out for the network to improve the speech quality.
Nokia’s BSC provides a better speech quality during handovers.</p>


<p>The channel rate is the primary requirement in assignment
and in external handover if alternatives (for example, channel rate or speech
coding) are given. Additional requirements are also taken into account in
all handovers from TCH to TCH. Such a requirement can be the prohibition of
rate changes after first channel allocation. If channel rate or speech codec
changes are allowed and a change is needed because of channel configuration
in the BTS, primarily speech codecs are changed inside the channel rate and
secondarily between channel rates.</p>


<p>The BSC also supports the use of pools, if needed. With
pools the BSC makes checks to ensure that the requirements upon the TCH in
question coincide with the properties of the pool before assignment may continue.
The BSC is also able to handle BTSs supporting and not supporting EFR. This
functionality requires no input from the operator; the BTS capability for
EFR is automatically checked by the BSC when the BTS is being reset. This
is important if not all the BTSs have been updated to support EFR. It is emphasised
that no configuration at the Abis interface is needed for EFR. Any TCH configured
to support FR at the Abis interface can be activated with EFR depending solely
on the properties of the BTS.</p>


<p>EFR is an optional feature in BSC.</p>
</div>


<a name="mar1841226393" shape="rect"></a>
<div class="topic">
<h2>TC</h2>

<p>In the Nokia GSM System, the existing FR Transcoder and
Submultiplexers (TCSMs) can be retained in the network to handle calls made
on full rate while the new generation of Transcoders Submultiplexers (TCSM2s)
can be SW upgraded or added to handle extensions and addition of EFR capability.</p>


<p>TCSM2 equipment was originally introduced for HR speech
coding purposes.</p>


<p>Having Nokia BSS, the MSC shall support circuit pools as
specified by ETSI for the A interface (GSM TS 08.02 and 08.08), if TCSM equipment
is meant to be used after support for EFR, it is introduced. The same applies
to HR. The pool concept allows the utilisation of remote transcoders with
different speech coding capabilities. If pools are not supported and a speech
coding algorithm other than FR is also supported, all the existing TCSMs must
be replaced with TCSM2s.</p>


<p>TCSM2 equipment allows dynamic switching between different
speech coding algorithms when configured to support more than one channel
rate or speech coding algorithm. For example, the speech coding for one circuit
carrying one TCH may vary between FR, EFR, and HR (as a result of handovers
for MS) at the Ater interface during one speech call.</p>
</div>


<a name="mar1841229174" shape="rect"></a>
<div class="topic">
<h2>MSC</h2>

<p>Having Nokia BSS, the MSC shall support circuit pools as
specified by ETSI for the A interface (GSM TS 08.02 and 08.08). The support
for EFR in the MSC mainly requires the capability to select appropriate resources
based on the information received from the MS and relaying that information
to the BSS. Since remote transcoders are in use in the Nokia BSS, the pool
concept shall be supported.</p>
</div>


<a name="mar1841229505" shape="rect"></a>
<div class="topic">
<h2>Transmission
lines</h2>

<p>From the transmission point of view, an EFR TCH is like
any FR TCH. In Nokia GSM system, the BSS provides flexible transmission solutions
and uses effectively the capacity of PCM lines (2Mbit/s). The optimisation
of the use of 2 Mbit PCM lines can be realised on both, A interface (BSC-MSC)
and the Abis interface (BSC-BTS), thus using the network resources efficiently.</p>
</div>


<a name="mar1841230336" shape="rect"></a>
<div class="topic">
<h2>MS</h2>

<p>New generation mobile stations (MSs) capable of supporting
EFR as defined in the specification are needed in order to use the feature.</p>


<a name="apr164123871" shape="rect"></a>
<div>
<img alt="urn:mars:dn0470134:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0470134&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Enhanced Full Rate Codec (ETSI)</p>
</div>


<p>The basic information of a codec type comes from the MSC.
The BSC will make the final decision about the codec based upon input from
the MSC, the BSS speech codec capabilities, and possibly radio channel conditions.</p>


<p>In case of handover, the BSC has the option to change the
speech codec at the time of handover. For intra-BSC handover, the BSC uses
the previously stored information from the MSC/VLR about the speech codec
preferences in the selection process.</p>


<p>The BSC forwards the information of codec type to the BTS
in the channel activation message. The BTS uses this information to configure
activated RTSL to support either conventional full rate codec or EFR. Inband
signalling between transcoder and BTS is used to control the transcoder codec
selection on a call basis.</p>
</div>
</div>
</body>
</html>