Huawei Airbridge BTS3612A-1900 Technical Manual page 55

Technical Manual
Airbridge BTS3612A CDMA Base Station
I. GPS
The GPS is a high precision all-weather satellite navigation system based on radio
communications. It can provide high precision information about 3D-position, speed
and time. The 3D-position is accurate to less than 10 yards (approx. 9.1m) in space; the
time is accurate to less than 100ns in time.
The GPS signals can be received and used as the reference frequency.
The whole system consists of three parts: space part, land control part and user part.
The space part is a group of satellites (altogether 24) 20,183 kilometers high, orbiting
the earth at a speed of 12 hours/circle.
The land control part consists of a main control center and some widely distributed
stations.
The user part includes GPS receivers and their supporting equipment.
II. GLONASS
The GLONASS is a global satellite navigation system developed by the former Soviet
Union and inherited by Russia. With 24 satellites distributed on 3 orbits, it has a
structure similar to the GPS, but a smaller coverage.
III. Application of GPS and GLONASS in CDMA BTS
The BTS3612A supports GPS/GLONASS satellite system synchronization mode,
providing two synchronization solutions (GPS or GPS/GLONASS) as required by the
user.
In the CDMA2000 1X system, the BTS is a user of the GPS or GLONASS, utilizing their
timing function. BTS3612A adopts smart software phase-lock and holdover
technologies to minimize interference such as signal wander and jitter caused by
ionosphere and troposphere errors of GPS or GLONASS satellites.
The timing signal of the GPS or GLONASS features high reliability and long-term
frequency stability. BTS3612A is equipped with a crystal clock that promises high
stability. The short-term stability of this crystal clock and the long-term stability of the
GPS or GLONASS combine to ensure the reliability and stability of the CDMA2000 1X
system clock.
Chapter 4 Antenna & Feeder Subsystem
4-6
System Principle