Gr-gsm's receiver needs a stream of samples with sampling frequency that
is integer multiply of gsm symbol rate. Many hardware receivers don't
support such rates, and even if they do there might be error in their
time source. Sample rate is adapted and corrected with use of a resampler.
Moreover corrections are applied in the runtime so resampler's resample
rate is changed dynamically. Those changes need to be tracked in order
to be able to track time of the hardware after resampling.
Hardware time tracking is needed to enable triggering of events in the
hardware (i.e. frequency changes, burst transmissions).
Changes were made in time_sample_ref and receiver in order to enable
SDR hardware time tracking.
Change-Id: Ide8149a5fc6c22700d3a4542115306a4dc682ff2
Piotr Krysik