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<div class="div">
<h1>MS Speed Detection</h1>

<p>The MS Speed Detection feature is designed to determine
the speed of the MS in GSM 900/1800 networks so that the fast moving mobiles
can be directed to macrocells and the slower mobiles respectively to microcells
thus decreasing the number of handovers in microcells.</p>


<p>The MS speed detection is a joint operation between the
BSC and Nokia BTS. The role of the BTS is to measure the MS speed and to send
the measured MS speed information to the BSC by including the speed information
in the Measurement Result message. The handover decision algorithm in the
BSC verifies the MS speed indications sent by the BTS. The adjacent cell layer
definitions are used with this feature. If an MS is detected as a fast moving
MS, it will be handed over to a upper layer cell (that is, a macrocell) if
any are available. The mobiles detected as slow moving mobiles will be handed
over to lower layer cells (that is, microcells) if any available. The MS Speed
Distribution Measurement is used to collect statistics of the MS speed distribution
on cell basis.</p>


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<h2>Various
Windows Size</h2>

<p>The basic idea of the MS Speed Detection feature is to
keep the fast moving MS's in  macro cells and direct the slow moving MS's
into micro cells. However, some operators have different strategies for traffic
distribution. It is suggested not to use Speed Information as a micro to macro
handover indication because ‘Speed’ itself has different interpretations in
different locations. Therefore, it is reasonable to have variable window size
(that is, Better Cell Trigger / Quality Trigger ) according to the speed indication.</p>


<p>Principally, a high-speed MS should use shorter average
window size, and a low-speed MS should use longer average window size. Therefore,
all averaging-processes should have two sets of widow parameters, one set
for high speed MS and one set for low speed MS. By applying a variable window
size, fast-moving MSs have shorter window size, and they may handover to target
cell faster. For a slow-moving MS, a longer window size is applied in order
to prevent it from unnecessary oscillation.</p>
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