User's Manual

Table Of Contents
Base Station Equipment
BreezeMAX Modular Base Station System Manual 11
1.2.9 Air Ventilation Unit (AVU)
The 2U high AVU includes a 1U high integral chamber for inlet airflow and a 1U
high fan tray with an internal alarm module. To support high availability Base
Station, the fan tray includes 10 brush-less fans, where 9 fans are sufficient for
cooling a fully loaded chassis. A failure in any of the fans is indicated by both the
front panel LEDs and a trap that is sent to the management system. To further
support high availability, the chassis may operate with the hot-swappable fan tray
extracted from it for a period of time sufficient for replacing it (up 10 minutes).
1.2.10 GPS
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 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.
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. A 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.
Table 1-2: PSU Requirements, Configurations with one NPU (excluding PSU redundancy)
Number of AU-IDUs Minimum Required
Number of PSUs
1 - 2 1
3 - 4 2
5 - 6 3