Motorola DIMETRA MTS 2, Инструкция по установке, настройке и базовому обслуживанию

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MTS 2 and MTS 4 Installation, Con
fi
guration and Basic Service Manual Tracking Criteria
•
Non-GPS / Non-Synchronized mode
The Non-GPS / Non-Synchronized mode introduced in System Release D6.1 guarantees
frequency accuracy of the site reference and the introduction of a Network Time Server (NTS)
using Network Time Protocol (NTM) allows the MTS to operate in non-synchronized mode
without being characterized as a malfunction and with accurate frequency and Network time.
When the BTS is GPS non-synchronized and without GPS and if a NTS is
available the NTP time shall be used to maintain and adjust frequency stability,
network time for UTD and timestamps for BTS log.
If GPS is not available and NTS are con
fi
gured with IP address(es) the time derived
from NTP shall be used for UTD and time stamping of BTS logs.
Only if the selected NTS are of suf
fi
cient accuracy and the BTS is con
fi
gured for
“Allow NTS frequency locking” shall the NTS be used for frequency locking of the
OCXO. The usability of the NTS shall be based on NTS alarm condition, Stratum,
Precision, root distance, reference ID and reference time.
If GPS is not available and NTS is con
fi
gured and allowed for locking and the BTS cannot
establish the connection to the NTS or the NTS is not usable for a period of more than a
NTS_Free_Run_Timer the operator shall be informed the NTS is failing.
Tracking Criteria
To allow a system to successfully initialize for the
fi
rst time at a new location, the Position
Dilution Of Position (PDOP) must be less than 2.0. A low PDOP value indicates a low error
(higher accuracy) in the position calculated by the GPS receiver.
PDOP is an accuracy factor, which is a function of the relative positions of the satellites. If the satellites being
tracked by the GPS receiver are within close relative proximity to each other, the resulting PDOP will be poor.
Conversely, if the satellites are relatively far from each other, PDOP will be improved. Because any error in
position results in a timing error in the BR transmission, the BRs are not allowed to key until the position error
is acceptably low. Therefore, a site with a large PDOP value may incur a delay when the site is
fi
rst initialized.
It is essential that after FRU replacement or moving the Site Controller in some
other manner, the position memory is reset using MMI commands.
Excessive PDOP values may be the result of the GPS receiver not having an adequate “view” of
the sky to initially determine its position. Motorola recommends locating the antenna(s) such that
there are no PDOP values that exceed 10.0 for periods of more than 15 minutes. To maintain a
maximum reliability, four satellites should be tracked at all times.
The system must be capable of the following:
•
Tracking a minimum of four satellites during initial start-up
•
Sustaining PDOP less than 10
•
Working in 3D
fi
x mode for the most of the time
6802800U74-N September 2009
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