User's Manual Part 2

Download the BTS – continued
DRAFT
SC4812ET BTS Optimization/ATP — CDMA LMF
Apr 2001
3-30
Enable CSMs
Each BTS CSM system features two CSM boards per site. In a typical
operation, the primary CSM locks its Digital Phase Locked Loop
(DPLL) circuits to GPS signals. These signals are generated by either an
on–board GPS module (RF–GPS) or a remote GPS receiver (R–GPS).
The CSM2 card is required when using the R–GPS. The GPS receiver
(mounted on CSM 1) is used as the primary timing reference and
synchronizes the entire cellular system. CSM 2 provides redundancy (but
does not have a GPS receiver).
The BTS may be equipped with a LORAN–C LFR, HSO, or external 10
MHz Rubidium source which the CSM can use as a secondary timing
reference. In all cases, the CSM monitors and determines what reference
to use at a given time.
For RF–GPS, verify the CSM configured with the GPS
receiver “daughter board” is installed in the frame’s CSM 1
slot before continuing.
IMPORTANT
*
Follow the steps outlined in Table 3-16 to enable the CSMs installed in
the C–CCP shelves.
Table 3-16: Enable CSMs
Step Action
1
Click on the target CSM.
From the Device pull down, select Enable.
NOTE
If equipped with two CSMs, enable CSM–2 first
A status report is displayed confirming change in the device(s) status.
Click OK to close the status report window.
NOTE
FAIL may be shown in the status table for enable action. If Waiting For Phase Lock is shown in the
Description field, the CSM changes to the Enabled state after phase lock is achieved.
CSM 1 houses the GPS receiver. The enable sequence can take up to one hour (see below).
* IMPORTANT
The GPS satellite system satellites are not in a geosynchronous orbit and are maintained and operated
by the United States Department of Defense (D.O.D.). The D.O.D. periodically alters satellite orbits;
therefore, satellite trajectories are subject to change. A GPS receiver that is 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).
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