User Manual

Chapter 3 - Operation and Administration of the Macro BTS NPU Configuration
4Motion 420 System Manual
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.
 External 16MHz: Generates all the main clocking signals in the system,
including the internal 1PPS clock. Using an external, accurate 16 MHz clock
source will enable better hold-over of the 1PPS clock upon temporary loss (or
reduced reliability when receiving less than 4 satellites) of the external 1PPS
clock. This will allow a longer time of continued operation before appearance of
interferences due to clock drifts among BSs. You can either enable the
external 16 MHz clock source or use the internal 16 MHz clock source. By
default, the external 16MHz clock is disabled. In the current release external
16MHz clock must be disabled.
To configure the GPS clock, run the following command:
npu(config)# set clock ([ External1PPS {Enable | Disable} ] [
External16MHz {Enable | Disable} ])
For example, to configure the internal 1PPS clock at the NPU to synchronize the
air frames for inter-site and intra-site sectors:
npu(config)# set clock External1PPS Disable
NOTE
If the external 1PPS GPS clock is enabled:
 The concatenated slave NPU 16Mhz created from local 16MHz TCXO/OCXO at the NPU
provides holdover when the GPS loses synchronization with its satellites.
 Configure the GPS parameters listed in section, Section 3.4.16.2.2.
IMPORTANT
Reset the system for changes in the GPS clock configuration to be applied to the entire system.
Command
Syntax
npu(config)# set clock ([External1PPS {Enable | Disable}] [External16MHz {Enable | Disable}])