Abstract

1
Development and application of CDMA and OFC
communication technology in ground based GPS
sensor network in Northeast China
Zhang Jingjiang Zhang Chaolin Institute of
Urban Meteorology (IUM), CMA, Beijing, China
Abstract Up to the 1st quarter of this year,
there are 48 ground-based GPS observation
stations in Northeast China, they belong to
Beijing Meteorological Bureau(BMB), Beijing
Municipal Government and China Meteorological
Administration (CMA), respectively. The Bernese
GPS software is used to do the post-processing
work. By the cooperation with NCAR/UCAR, BMB can
calculate GPS-derived precipitable water vapor of
Northeast China almost in real time (less than 2
hours delay). The operational GPS-Met products
include the PWV variation charts in Northeast
China (every 30 minutes), meteorological elements
(air pressure, temperature and relative humid )
variation at each stations and (every 30 minutes)
and GPS water-vapor topography at Fangshan area
in Beijing (2 days delay). Data assimilation of
GPS PWV has been put into the MM5 NWP and LAPS
system successfully. By support of Beijing
Municipal Science and Technology Commission, BMB
has set up 14 stations at the end of 2004. These
14 stations are divided into two group , one
group is located in Fangshan county which
includes 8 stations , the other group is in
Huairou county which includes 6 stations. BMB has
developed a GPS data communication system based
on the CDMA wireless telecommunication
technology. Therefore, the observation data can
be transmitted to BMB in every 30 minutes with no
more than 10 minutes delay. The bandwidth is
about 100kbps. The Beijing Municipal Government
has invested to build 16 GPS stations in each
county of Beijing area for civilian use, most of
them are built in local weather station. Optical
fiber cables (OFC, 2M ) connect to the stations
so observation data can be get in real
time. Both of CDMA and OFC can be used to
reliably transfer data in real-time. CDMA does
meet the requirement of operational demand,
though its bandwidth is narrower than OFC. Since
it takes less money and time to set up data
transferring links by CDMA than by OFC, it is
more suitable for those stations in remote area,
where stations are not man-operated.
The operational GPS-Met products
GPRS/CDMA Data Transfer Topology Network
Data Transfer System based on PSTN
Location of GPS site in North China
Optical fiber cables instrument
CDMA Instrument