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<div class="div">
<h1>Advanced Multilayer Handling (AMH)</h1>

<p>The Nokia Advanced Multilayer Handling (AMH) concept is
used to redistribute traffic to the appropriate layer or frequency band according
to the prevailing load of the network. Therefore, AMH can smooth out the traffic
over the network. This procedure is also supported on an inter-BSC basis.</p>


<p>The AMH concept consists of three different features, which
are related to network load:</p>


<ul>
<li><p>BSC initiated Traffic Reason Handover</p>
</li>
<li><p>IUO load control</p>
</li>
<li><p>Multilayer load control.</p>
</li>
</ul>


<p>The AMH concept is feasible especially in multi-band (the
GSM900/GSM1800), micro cellular or multilayer (the Nokia Intelligent Underlay
Overlay) networks by providing the operator both improved quality and capacity.</p>


<p>The AMH provides the network operator with the tools to
relief load of the congested cells and smooth out the load over the network.
It provides also operators with the tools to use only overlay network during
low traffic periods thus avoiding additional handovers between two layers.
Therefore, it is extremely efficient in multilayer networks.</p>


<p>The AMH can also be applied efficiently with the Nokia
Intelligent Underlay - Overlay to avoid congestion in the overlay layer and
thus providing more trunking gain. The AMH is able to redistribute the traffic
from congested regular layer to other cells selecting the best mobile and
cell combination which is likely to survive and give good quality on the new
cell.</p>


<p>The AMH also includes tools to avoid additional handovers
(Ping-Pong) back to a heavy loaded cell by introducing a particular penalty
system. Therefore, the mobile stations cannot be directed back to the original
heavy loaded cell before the penalty timer is expired.</p>


<p>In general, by using the Nokia AMH and setting AMH related
parameters, operators can move the capacity between different layers according
to the prevailing traffic.</p>


<p>The following picture illustrates the AMH concept.</p>


<a name="apr154183351" shape="rect"></a>
<div>
<img alt="urn:mars:dn0468827:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0468827&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Overview of AMH concept</p>
</div>


<a name="mar241210281" shape="rect"></a>
<div class="topic">
<h2>BSC
initiated TRHO (Congestion relief)</h2>

<p>The AMH concept provides the network operator with the
tools to relief the load of the congested cells and smooth out the load over
the network. The overall traffic load of the network can be smoothed out by
using the BSC initiated TRHO feature. The basic idea of the feature is to
dynamically change the power budget margins and thus direct the MSs hanging
around in the cell border to less loaded adjacent cells.</p>


<p>The BSC initiated TRHO is based on radio frequency resource
indications of idle channel interference (that is, load information), which
are sent from the base transceiver station  (the BTS) to the base station
controller  (the BSC).  If the traffic load of the serving cell exceeds the
parameter <em>AmhUpperLoadThreshold</em> (set for each BSC
by means of the O&amp;M), <em>AmhTrhoMarginPBGT</em> (set
for each BTS by means of the O&amp;M) is used for all same layer adjacent
cells in the power budget equation instead of the existing <em>HoMarginPBGT</em>.
The basic evaluation algorithm calculated according to radio link properties
is based on the following strategy and order:</p>


<ol class="type-odd">
<li type="1"><p>AV_RXLEV_NCELL(n) &gt; TRHO_TARGET_LEVEL(n)
+  Max(0,(MS_TXPWR_MAX_CELL(n) - P))</p>
</li>
<li type="1"><p>PBGT (n) &gt; AmhTrhoMarginPBGT and PBGT
(n) &lt; HOMarginPBGT</p>
</li>
</ol>


<p>If the PBGT value is between AmhTrhoMarginPBGT and HOMarginPBGT,
the handover is triggered due to the TRHO handover. If the PBGT value exceeds
 HOMarginPBGT, the handover is triggered due to the PBGT handover.</p>


<p>Furthermore, the TRHO candidate has to have less than AmhMaxLoadOfTgtCell
(set for each BSC by means of the O&amp;M) reserved traffic channels in order
to become the target cell. The Radio Resource Management program block (RRMPRB)
maintains the status of available channels, and according to prevailing traffic,
can allow the TRHO channel allocation.</p>


<a name="mar24121322" shape="rect"></a>
<dl class="note-notification">
<dt class="note-caption">Note</dt>
<dd>Queuing is not used with the BSC initiated TRHO.</dd>
</dl>


<p>Sometimes the traffic has to be directed to weaker cells.
Therefore, a special mechanism for handling that kind of traffic, keeping
the call in the new cell, is also added to the concept. The parameter <em>TrhoGuardTime</em> (set for each BSC by means of the O&amp;M)
determines the penalty time to handover back to the original cell because
of the PBGT handover, and therefore consecutive handovers back to original
cell during the guard time is prevented.</p>


<a name="mar241213483" shape="rect"></a>
<dl class="note-notification">
<dt class="note-caption">Note</dt>
<dd>The parameter<em>TrhoGuardTime</em> is
also be used with the MSC controlled handover.</dd>
</dl>


<a name="apr1541810462" shape="rect"></a>
<div>
<img alt="urn:mars:dn0468815:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0468815&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: BSC initiated TRHO</p>
</div>


<a name="mar24121534" shape="rect"></a>
<dl class="note-notification">
<dt class="note-caption">Note</dt>
<dd>Only calls from the regular layer can be redirected due
to the traffic reason handover.</dd>
</dl>
</div>


<a name="mar241215345" shape="rect"></a>
<div class="topic">
<h2>IUO
load control</h2>

<p>The IUO is applied into the network to increase capacity.
On the other hand in periods where the capacity needs are not so high, the
IUO functionality is still performing many handovers. Therefore, by avoiding
additional handovers between different frequency layers, the quality of the
network can be improved.</p>


<p>The AMH can be used to prevent the use of the IUO during
very low traffic and thus keep the mobiles only in the overlay network. The
solution is based on the traffic load of serving cell.</p>


<p>If the traffic load of the serving cell go under<em>AmhLowerLoadThreshold</em>,
the IUO handover, Direct Access to super-reuse TRX, and IUODR are not allowed.
The functionality is controlled by the parameter <span class="parameter-sem">AmhTrafficControlIUO</span>
(set for each BSC by means of the O&amp;M).</p>


<a name="apr1541811453" shape="rect"></a>
<div>
<img alt="urn:mars:dn0469035:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0469035&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: IUO load control</p>
</div>
</div>


<a name="mar241219216" shape="rect"></a>
<div class="topic">
<h2>Dual
band/micro cellular network load control</h2>

<p>Many operators build capacity by using micro cells or Dual
Band solution. The increasing amount of different network layers also increase
the number of handover between layers. During very low traffic, that is, during
nights, the need for extra capacity is unnecessary, and therefore underlay
capacity is not needed. The adequate capacity can be achieved by using only
the overlay network.</p>


<a name="apr1541812264" shape="rect"></a>
<div>
<img alt="urn:mars:dn0469008:1:en:global:tiff:data:data" border="0" src="NED?action=retrieve&amp;identifier=dn0469008&amp;edition=1&amp;language=en&amp;coverage=global&amp;encoding=gif&amp;component=data&amp;item=data" /><p class="figure-caption">Figure: Multilayer load control</p>
</div>


<p>On the other hand, during night-time most of the traffic
is accomplished outside, particularly from fast moving vehicles. Furthermore,
fast moving mobiles in the micro cell network generate many handovers with
relative high speed. Therefore, it is more reasonable to keep the traffic
in the overlay network instead of underlay to provide better quality to end-users.</p>


<p>The AMH can be used to prevent the use of micro cell/DCS
layer during very low traffic and thus keep the mobiles only in the macro/GSM
network once they have camped on it. </p>


<p>If the traffic load of the serving cell goes under AmhLowerLoadThreshold,
the FMMS, MS Speed Detection, and Umbrella handovers are not allowed to lower
layer cells. The functionality is controlled by the parameter AmhTrafficControlMCN
(set for each BSC by means of the O&amp;M).</p>


<a name="mar241220517" shape="rect"></a>
<dl class="note-notification">
<dt class="note-caption">Note</dt>
<dd>The access to micro cells cannot be prevented, but C2 reselection
can be used to keep the fast moving mobiles in the overlay network during
idle mode.</dd>
</dl>
</div>


<a name="mar24122478" shape="rect"></a>
<div class="topic">
<h2>Interaction
with other features:</h2>
</div>


<a name="mar241224249" shape="rect"></a>
<div class="topic">
<h2>Direct
Access to Desired Layer/Band</h2>

<p>AMH multilayer load control has lower priority than the
Direct Access to Desired Layer/Band (DADL/B) feature.</p>
</div>


<a name="mar2412245610" shape="rect"></a>
<div class="topic">
<h2>HSCSD</h2>

<p>The BSC initiated TRHO is only made for single-slot connections.
The parameter UpperLimitCellLoadHSCSD should be set to a greater value than
the parameter <em>AmhUpperLoadThreshold</em>. Thus unnecessary
downgrades are avoided and radio resources are used efficiently.</p>
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