User's Manual

Table Of Contents
Base Station Equipment
BreezeMAX Modular Base Station System Manual 13
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 sectors are operating with the same
frame size and with the same DL/UL ratio).
The GPS clock required is 1PPS with accuracy of 10
-11
and maximum jitter of
100ns. These GPS clock requirements can be reached by indoor or outdoor
installed GPS unit when it is synchronized to at least 4 satellites.
Two types of GPS Receivers are available from Alvarion:
Indoor GPS Receiver (with an outdoor antenna)
Outdoor GPS Receiver
A GPS Adapter is required to provide the interface between the NPU and the GPS
Receiver.
1.2.10.1 Indoor GPS Receiver
The Indoor GPS Receiver comprises a GPS receiver integrated with a stable OCXO
oscillator, within a unit designed for mounting in a standard 19 inch rack. An up
to 50 meter coaxial cable connects it to an active antenna. The indoor installed
GPS system is able to provide up to 40 hours of clock holdover with a maximal
drift of 50 microseconds when the GPS system losses satellites synchronization.
The Indoor GPS provides 1PPS at TTL levels and the control channel is driven by
an RS-232 serial interface. The unit is powered directly from a -48 VDC power
source.
1.2.10.2 Outdoor GPS Receiver
The all-outdoor GPS Receiver is a pole mountable GPS receiver and antenna in a
single environmentally protected enclosure. The Outdoor GPS Receiver is powered
by a 12 VDC power source, supplied to it by the NPU via the GPS Adapter. The
RS-422 interface allows installation at distances up to 100m.
1.2.10.3 GPS Adapter Unit
The GPS Adapter connects the different GPS units to the NPU, adapting the
different interfaces. Future versions may include an internal GPS module that will
allow an all-in-one low-cost solution. A future optional addition of OCXO in the
GPS Adapter box may provide an improved hold over solution when the GPS is not
synchronized. The GPS Adapter is powered by 12 VDC supplied by the NPU. The
GPS Adapter is installed in a 1U high panel (the same panel that is used for the
ODU Power Feeders).