Monitor

The Monitor block provides an interface for monitoring the internal status of the receiver in real-time by streaming the receiver’s internal data to local or remote clients over UDP.

This block is a feature of GNSS-SDR which was developed having usability in mind. It gives an internal (or white-box) perspective of the receiver, allowing a deeper insight into its performance, and provides a communication interface through which end-users can build their monitoring clients upon.

This is made possible by exposing Gnss_Synchro objects from inside the receiver to the user. These objects are special containers that hold a set of variables that capture the internal state of the receiver as they travel along the receiver chain.

Each channel of the receiver instantiates a Gnss_Synchro object. Once it reaches the Monitor block, the object is serialized into a binary encoded message and then streamed through a network socket to one or more destination endpoints (clients) designated by the user. Each client can then deserialize the encoded message from the data stream, recover the Gnss_Synchro object and access its member variables for further inspection and monitoring.

This communication mechanism is built with Boost.Asio for the networking logic and Protocol Buffers for the serialization logic. Originally Boost.Serialization was used but in release v0.0.11 it was deprecated in favor of Protocol Buffers. If you still wish to use the old serialization format based on Boost, set the Monitor.enable_protobuf parameter to false in your configuration file.

Exposed Internal Parameters

The exposed internal parameters are the data members of the Gnss_Synchro class. There are 25 in total, and can be classified based on the subsystem they inform about:

Satellite and signal information

The following set of variables record general information about the Channel.

Acquisition

The following set of variables record information about the Acquisition block.

Tracking

The following set of variables record information about the Tracking block.

Telemetry Decoder

The following set of variables record information about the Telemetry Decoder block.

Observables

The following set of variables record information about the Observables block.

Configuration

The configuration of the Monitor block accepts the following parameters:

Example 1:

The following configuration streams the receiver internal parameters to the localhost address on port 1234 UDP without decimation (observables every 20 ms):

;######### MONITOR CONFIG ############
Monitor.enable_monitor=true
Monitor.decimation_factor=1
Monitor.client_addresses=127.0.0.1
Monitor.udp_port=1234

Example 2:

The following configuration streams the receiver internal parameters to the addresses 10.10.10.1 and 10.10.10.2 on port 1234 UDP with a decimation integer factor of \(N=50\) (observables every 1 s):

;######### MONITOR CONFIG ############
Monitor.enable_monitor=true
Monitor.decimation_factor=50
Monitor.client_addresses=10.10.10.1_10.10.10.2
Monitor.udp_port=1234

Monitor listeners

Once your receiver is streaming data, you need a client listening on the other side.

Of course, you are free to develop other clients covering your specific requirements. All you need is the gnss_synchro.proto file, which allows you to write clients in Java, Python, C++, Objective-C, C#, Dart, Go, or Ruby.