Tracking Criteria; Gps Start Up - Motorola MTS LiTE Installation, Configuration And Basic Service Manual

6802800U74-AN
Chapter 4: Hardware Installation
This mode can be configured through TESS for compatibility reasons but will be treated as ASC.
• 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 an NTS is available the NTP time
shall be used to maintain and adjust frequency stability, network time for UTC (Coordinated
Universal Time) and timestamps for BTS log.
If GPS is not available and an NTS is configured with IP address, the time derived from NTP shall
be used for UTC and time stamping of BTS logs.
If the selected NTS is of sufficient accuracy and the BTS is configured for "Allow NTS frequency
locking" the NTS is used for frequency locking of the Oven-Controlled Crystal Oscillator (OCXO), a
type of crystal oscillator used to control the frequency of transmitters, base stations, and other
communications equipment. The usability of the NTS is based on NTS alarm condition, Stratum,
Precision, root distance, reference ID, and reference time.
If GPS is not available and NTS is configured 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 an
NTS_Free_Run_Timer the operator is informed by the GPS AND NTS LOST alarm that the NTS is
failing.
4.8.2

Tracking Criteria

To allow a system to successfully initialize for the first 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. A site with a large PDOP value may incur a delay when
the site is first initialized.
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
is poor. Conversely, if the satellites are relatively far from each other, PDOP improves. 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.
CAUTION: After FRU replacement or moving the Site Controller in some other manner, the
position memory is reset using MMI commands.
Excessive PDOP values may result from the GPS receiver not having an adequate view of the sky to
initially determine its position. Motorola Solutions recommends locating the antennas such that there
are no PDOP values that exceed 10.0 for periods of more than 15 minutes. Maintaining a maximum
reliability requires tracking four satellites at all time.
Site Reference requirements for proper operation:
• Tracking a minimum of four satellites during initial start-up
• Sustaining PDOP less than 10
• Working in 3D fix mode for the most of the time
4.8.3

GPS Start Up

GPS startup is the significant contributing factor in determining system start up times. The start up
times are counted from applying power to the system until GPS LED is solid green illuminating.
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