User's Manual

Chapter 3 - Operation and Administration Using the CLI NPU Configuration
4Motion 384 System Manual
The GPS clock generates a 1PPS signal and is connected to the 4Motion shelf via
the GPS SYNC IN connector on the front panel of the NPU. The GPS clock
requirements can be reached by an outdoor installed GPS unit when it is
synchronized to a minimum number of (user-configurable) satellites.
This section describes the commands to be used for:
 “Configuring the GPS Clocks” on page 384
 “Configuring General Configuration Parameters for the GPS” on page 387
 “Configuring the Date and Time” on page 388
 “Configuring the Position” on page 390
 “Configuring the Required Number of Satellites” on page 391
 “Displaying GPS Clocks Parameters” on page 392
 “Displaying GPS General Configuration Parameters” on page 393
 “Displaying the Date and Time Parameters” on page 394
 “Displaying the Position Parameters” on page 395
 “Displaying the Number of Satellite Parameters” on page 395
3.3.15.2.1 Configuring the GPS Clocks
The GPS clock parameters determines the source for the main clocks in the
system. To configure the GPS clock, you are required to enable/disable:
 External 1PPS: Determines the air-frame start time. Assuming that all systems
use the same air-frame size and DL/UL Ratio, then, when the 1PPS clock is
received from a GPS system, this mechanism ensures inter-site and intra-site
synchronization among all sectors, preventing cross interference and
saturation problems. When using the internal 1PPS clock (derived from the
selected 16 MHz clock source), only intra-site synchronization among sectors
can be achieved. You can either enable the external 1PPS clock source or use
the internal 1PPS clock source derived from the selected 16 MHz clock. By
default, the External IPPS clock is enabled. When using a GPS for
synchronization, the 1PPS clock is received from the GPS receiver and must be
enabled for proper operation.