These messages duplicate ADS-B messages so it's not clear why
they are being interrogated for, and we don't really trust them
enough to do anything with the position information. But
recognizing/decoding them where possible does let us exclude other
Comm-B message types, avoiding some false positives.
The legacy -10 value is still supported for compatbility with old
configs, but new configs should just select an appropriate gain e.g.
60dB.
rtlsdr default gain continues to be the highest regular gain step (~ 49.6dB)
on upgrade to 6.0. (Not extensively tested yet)
We do this for two reasons:
1) the config file layout is completely different, it's error-prone
and tedious to force the user to manually transfer their customizations
on upgrade;
2) if there are user modifications to the config file, an upgrade triggered
remotely via piaware will prefer to keep the original config file intact
rather than installing the new version, and the old version just won't
work correctly with the new infrastructure.
Now we have specific config options for different features rather
than just a big list of command-line options. You can still provide
custom options via EXTRA_OPTIONS or OVERRIDE_OPTIONS.
Also adds adaptive gain settings, and a "slow cpu" setting which
can turn on cpu-reducing options automatically when a slower (armv6)
CPU is in use.
This makes the adaptive gain code only process some fraction of all samples,
rather than every sample. This helps a lot with CPU on slower machines.
We default to a 50% duty cycle to save some CPU without really affecting
the behavior much.
We split the one-second adaptive gain blocks into 20* 50ms "subblocks"
Each subblock is either entirely processed or not processed at all,
based on the configured duty cycle. (This means that the duty cycle
can only be specified in approx 5% increments, but that should be
fine)
For adaptive dynamic range, there's no further complications - we
just look at fewer samples to compute the noise floor.
For adaptive burst, we need to scale up the measured burst rate by
1/duty cycle to account for the samples that we didn't process. It's
also more likely to cause functional changes as it's quite possible
for a relatively small number of loud messages being missed to
affect the computed rate substantially. Not many options there other
than increasing the duty cycle when adaptive burst handling is wanted.
Update adaptive gain control loop to handle interactions between burst detection and dynamic range control.
Internal doc updates & naming cleanups.
Stats tweaks.
This PR adds basic adaptive gain support, which adjusts SDR gain on the fly based on the noise & signal levels seen.
There are two control mechanisms:
Dynamic range control is enabled by the --adaptive-range option. This adjusts SDR gain to try to achieve a minimum dynamic range, regardless of the exact hardware in the RF path.
Burst (loud message) control is enabled by the --adaptive-burst option. This decreases SDR gain when undecodable loud messages are heard, allowing for better reception of nearby aircraft at the expense of range.
This is only the basic implementation - see the PR for remaining work to do.
Oliver Jowett
Adrian Batzill
VirusPilot
wiedehopf
eric1tran
Matthias Wirth
Eric Gideon
Chris Carini