User's Manual

CSM System Time – GPS and HSO Verification

FEB 2005 1X SC 4812T Lite BTS Optimization/ATP 3-47

PRELIMINARY

Clock Synchronization

Manager (CSM) Subsystem

Description

Overview

Each BTS CSM Subsystem features two CSM Cards per RF Modem

Frame. The primary function of the CSM Cards is to maintain CDMA

System Time. GPS is used as the Primary Timing Reference and

Synchronizes the entire Cellular System.

In typical operation, the Primary CSM locks its Digital Phase Locked

Loop (DPLL) Circuits to GPS Signals. These signals are provided by

either an on–board GPS Receiver Module (RF–GPS) or a Remote GPS

Receiver (RGPS).

RGPS uses a GPS Receiver in the Antenna Head that has a Digital

Output. The second generation CSM Card (CSM–II) is required when

using the RGPS. A CSM–II Card can also be equipped with a Local

GPS Receiver Daughter Card to support an RF–GPS Signal..

SCCP Cage CSM Card Slot Assignments

The GPS Receiver is interfaced to the CSM Card in SCCP Cage Slot

CSM 1. This card is the Primary Timing Source, while the CSM Card in

Slot CSM 2 provides Redundancy. The redundant card, does not have a

GPS Receiver..

CSM–II Card Type Description

Each CSM–II Card features a temperature–stabilized Crystal Oscillator

that provides 19.6608 MHz Clock, Even–Second Pulse, and 3 MHz

Reference Signals to the Synchronization Source selected from the

following list.

– Refer to Table 3-24 for Source Selection/Verification Procedures..

S GPS: Local/RF–GPS or Remote/RGPS

S High Stability Oscillator (HSO)

S External Reference Oscillator Sources

CDMA Clock Distribution Card (CCD) Description

CCD Cards buffer and distribute Even–Second Reference and 19.6608

MHz Clock Signals from the CSM Cards. CCD 1 is married to the CSM

1 Card in the CSM 1 Slot, and CCD 2 is married to the CSM 2 Card in

Slot CSM 2..

CSM Card Redundancy

The BTS switches between the Primary and Redundant units (Card

Slots CSM 1 and CSM 2, respectively) upon failure or command. A

failure in CSM 1 or CCD 1 will cause the system to switch to the

CSM 2/CCD 2 Redundant Card Pair. GPS Timing Synchronization is

continually maintained between the Primary and Redundant CSM/CCD

Pairs..