User's Manual

Chapter 1 - System Description BreezeMAX Extreme
BreezeMAX Extreme 15 System Manual
1.3.6 GPS Antenna
GPS is used to synchronize the air link frames of Intra-site and Inter-site located
sectors to ensure that in all sectors the air frame will start at the same time, and
that all sectors will switch from transmit (downlink) to receive (uplink) at the same
time. This synchronization is necessary to prevent Intra-site and Inter-site sectors
interference and saturation (assuming that all neighboring sectors are operating
with the same DL/UL ratio).
The BTS includes an internal GPS receiver with hold over mechanism in case GPS
is lost or satellites synchronization was not reached. The GPS clock required is
1PPS with accuracy of 10
-11
and maximum jitter of 100ns. These GPS clock
requirements can be reached by a GPS receiver when it receives at least 4
satellites. After initial synchronization, at least two satellites should be received to
maintain sufficient synchronization.
Alvarion offers two types of GPS antennas:
 Active high-gain antenna that can be installed at a distance of up to 25m from
the BTS.
 Basic miniature antennas that can be installed at a distance of up to 3m from
the BTS.