CN0 Estimator

The CN0 (Carrier-to-Noise density ratio) estimator provides a measure of signal quality in dB-Hz.

Default Estimator

The default CN0 estimator is the Moment Method implemented as MomentsCN0Estimator. It buffers prompt correlation values and estimates CN0 based on the signal and noise power moments.

You can adjust the buffer size for the MomentsCN0Estimator when creating a SatState:

sat_state = SatState(
    system, prn, code_phase, carrier_doppler,
    num_prompts_for_cn0_estimation = 100  # Buffer size for MomentsCN0Estimator
)

Estimating CN0

To get the CN0 estimate from a tracking state:

julia> using Tracking, GNSSSignals

julia> using Tracking: Hz

julia> system = GPSL1();

julia> sat_state1 = SatState(system, 1, 50.0, 1000.0Hz);

julia> sat_state2 = SatState(system, 5, 120.0, -500.0Hz);

julia> track_state = TrackState(system, [sat_state1, sat_state2]);

julia> estimate_cn0(track_state, 1)  # Access by PRN
0.0 dB-Hz

julia> estimate_cn0(track_state, 5)  # Access by PRN
0.0 dB-Hz

Note: CN0 will be 0.0 dB-Hz until actual signal data has been processed through the tracking loop.

estimate_cn0(estimator, integration_time)

Custom CN0 Estimators

You can implement your own estimator by creating a subtype of AbstractCN0Estimator and implementing the following functions:

• update(cn0_estimator::MyCN0Estimator, prompt): Update the estimator with a new prompt value
• estimate_cn0(cn0_estimator::MyCN0Estimator, integration_time): Return the CN0 estimate

Pass your custom estimator when creating a SatState:

julia> prn = 1;

julia> code_phase = 50.0;

julia> carrier_doppler = 1000.0Hz;

julia> num_prompts = 100;  # Buffer size for MomentsCN0Estimator

julia> sat_state = SatState(
           system, prn, code_phase, carrier_doppler,
           num_prompts_for_cn0_estimation = num_prompts
       );

Pass your custom estimator to a SatState:

sat_state = SatState(
    sat_state;
    cn0_estimator = MyCN0Estimator()
)