User's Manual

Download the BTS – continued

3-44 1X SC 4812T Lite BTS Optimization/ATP FEB 2005

PRELIMINARY

Selecting CSM Clock Source

and Enabling CSM Cards

CSM Cards must be enabled prior to enabling the MCC Cards.

Procedures in the following two sub-sections cover the actions to

accomplish this. For additional information on the CSM Subsystem, see

“Clock Synchronization Manager (CSM) Subsystem Description” in the

CSM System Time – GPS and HSO Verification section of this chapter.

GPS Satellite System

The GPS Satellite System Satellites are maintained and operated by the

United States Department of Defense (DOD). The DOD periodically

alters satellite orbits; they are not in geo–synchronous orbits. Therefore,

satellite trajectories are subject to change.

A GPS Receiver that is in service (INS) contains an “Almanac” that is

updated periodically to take these changes into account.

– If a GPS Receiver has not been updated for a number of weeks, it

may take up to an hour for the GPS Receiver “Almanac” to be

updated.

– Once updated, the GPS Receiver must track at least four satellites

and obtain (hold) a 3–D position fix for a minimum of 45 seconds

before the CSM will come in service. In some cases, the GPS

Receiver needs to track only one satellite, depending on Accuracy

Mode set during the Data Load.

Select CSM Clock Source

A CSM can have three different Clock Sources. The Select CSM Source

Function can be used to select the Clock Source for each of the three

inputs. This function is only used if the Clock Source for a CSM needs

to be changed. The Clock Source Function provides the following Clock

Source Options.

S Local GPS

S Mate GPS

S Remote GPS

S HSO (only for Sources 2 and 3)

S HSO Extender

S 10 MHz (only for Sources 2 and 3)

S NONE (only for Sources 2 and 3)

Prerequisites

S MGLI is INS_ACTIVE (bright green)

S CSM is OOS_RAM (yellow) or INS_ACTIVE (bright green)

Perform the procedure in Table 3-19 to select a CSM Clock Source.