Monitor/Control Station
Hardware/Software Architecture
The recommended hardware/software architecture for the NAVSTAR Monitor Stations
and/or Control Stations is depicted below. The architecture is the same for both
monitor and control (satellite uplink) stations; the distinction between the two is in the
direction of communications flow and the presence of an antenna position control
element in the control station. This architecture is composed of COTS products to the
maximum extent possible, with DCE middleware used to provide a standardized
API/RPC environment for GPS applications software. Custom hardware and software
components and interfaces will only be used where no commercial equivalent exists
and a compelling need exists to maintain a proprietary interface.
This redesigned architecture has the following advantages:
- Redundant COTS fault-tolerant hardware/software are utilized for the monitor and/or
control processing elements. One is active at any given time, while the second is in
"monitor/hot standby" mode in the event of failure of the active unit. Synchronization
can be achieved by periodic comparison of system information during otherwise idle
times.
- Use of a real-time operating system may not be required due to the increased
processing power now available.
- DCE middleware is used to provide a standard API/RPC environment for GPS
applications software. This middleware also performs TCP/IP to GPS-unique
conversions for data to be transmitted to/received from SVs.
- TCP/IP is used as the protocol stack for both internal and external communications.
The protocol stacks used at this location are shown below:
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