User's Manual

The Base Transceiver Station
4Motion System Manual 21
For more information on recommended antenna configurations and required
antennas refer to Appendix A.
1.3.10 GPS
GPS is used to synchronize the air link frames of Intra-site and Inter-site located
Base Transceiver Stations to ensure that in all Base Stations the air frame will
start at the same time, and that all Base Stations will switch from transmit
(downlink) to receive (uplink) at the same time. This synchronization is necessary
to prevent Intra-site and Inter-site interference and Base stations saturation
(assuming that all Base Stations are operating with the same frame size and with
the same DL/UL ratio).
In order for the system to be synchronized, the GPS have to first acquire at least 4
satellites. After that the GPS reception can be reduced to 1 satellite.If no satellite
is received the BTS will go to holdover state where internal clock is provided to
synchronize the BTS.
1.3.10.1 Outdoor GPS Receiver
The all-outdoor GPS Receiver is a pole mountable GPS receiver and antenna in a
single environmentally protected enclosure. The GPS Receiver is powered by a 12
VDC power source, supplied to it by the NPU. The RS-422 interface allows
installation at distances up to 100m.