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#!/usr/bin/env python
##################################################
# Gnuradio Python Flow Graph
# Title: GSM wideband input adaptor
# Author: Piotr Krysik
# Co-author: Pieter Robyns
# Description: Adaptor of input stream for the GSM receiver. Contains frequency ofset corrector doing also resampling to integer multiplies of GSM sample rate and LP filter filtering GSM channel.
##################################################
from gnuradio import filter
from gnuradio import gr
from gnuradio import eng_notation
from gnuradio.filter import firdes
import grgsm.arfcn as arfcn
import grgsm
class gsm_wideband_input(grgsm.hier_block):
def __init__(self, ppm=0, osr=4, fc=925.2e6, samp_rate_in=20e6, ca=[], band='P-GSM'):
self.num_streams = len(ca)
grgsm.hier_block.__init__(
self, "GSM wideband input adaptor",
gr.io_signature(1, 1, gr.sizeof_gr_complex*1),
gr.io_signature(self.num_streams, self.num_streams, gr.sizeof_gr_complex*1),
)
##################################################
# Parameters
##################################################
self.ppm = ppm
self.osr = osr
self.fc = fc
self.samp_rate_in = samp_rate_in
self.ca = ca
self.blocks_fir_filters = {}
self.blocks_resamplers = {}
self.blocks_ocs = {}
self.band = band
##################################################
# Variables
##################################################
self.samp_rate_out = samp_rate_out = 1625000.0/6.0*osr
##################################################
# Blocks
##################################################
self.ppm_in = None
self.message_port_register_hier_in("ppm_in")
#self.lpf = firdes.low_pass(1, samp_rate_out, 125e3, 5e3, firdes.WIN_HAMMING, 6.76)
self.lpf = firdes.low_pass(1, samp_rate_in, 125e3, 75e3, firdes.WIN_HAMMING, 6.76)
self.gsm_clock_offset_corrector_0 = grgsm.clock_offset_corrector(
fc=fc,
ppm=ppm,
samp_rate_in=samp_rate_in,
)
center_arfcn = arfcn.downlink2arfcn(fc, band)
fc_str = eng_notation.num_to_str(fc)
print("Extracting channels %s, given center frequency at %sHz (ARFCN %d)" % (str(ca), fc_str, center_arfcn))
self.connect((self, 0), (self.gsm_clock_offset_corrector_0, 0))
output_port = 0
for channel in ca:
channel_freq = arfcn.arfcn2downlink(channel, band)
if channel_freq is None:
print("Warning: invalid ARFCN %d for band %s" % (channel, band))
continue
freq_diff = channel_freq - fc
freq_diff_str = "+" if 0 <= freq_diff else ""
freq_diff_str += eng_notation.num_to_str(freq_diff)
print("ARFCN %d is at %sHz %sHz" % (channel, fc_str, freq_diff_str))
self.blocks_resamplers[channel] = filter.fractional_resampler_cc(0, samp_rate_in/samp_rate_out)
self.blocks_fir_filters[channel] = filter.freq_xlating_fir_filter_ccc(1, self.lpf, freq_diff, samp_rate_in)
self.connect((self.gsm_clock_offset_corrector_0, 0), (self.blocks_fir_filters[channel], 0))
self.connect((self.blocks_fir_filters[channel], 0), (self.blocks_resamplers[channel], 0))
self.connect((self.blocks_resamplers[channel], 0), (self, output_port))
output_port += 1
##################################################
# Asynch Message Connections
##################################################
self.msg_connect(self, "ppm_in", self.gsm_clock_offset_corrector_0, "ppm_in")
def get_ppm(self):
return self.ppm
def set_ppm(self, ppm):
self.ppm = ppm
self.gsm_clock_offset_corrector_0.set_ppm(self.ppm)
def get_fc(self):
return self.fc
def set_fc(self, fc):
self.fc = fc
self.gsm_clock_offset_corrector_0.set_fc(self.fc)
def get_osr(self):
return self.osr
def set_osr(self, osr):
self.osr = osr
self.set_samp_rate_out(1625000.0/6.0*self.osr)
def get_samp_rate_in(self):
return self.samp_rate_in
def set_samp_rate_in(self, samp_rate_in):
self.samp_rate_in = samp_rate_in
for channel in self.blocks_resamplers:
self.blocks_resamplers[channel].set_resamp_ratio(self.samp_rate_in / self.samp_rate_out)
self.gsm_clock_offset_corrector_0.set_samp_rate_in(self.samp_rate_in)
def get_samp_rate_out(self):
return self.samp_rate_out
def set_samp_rate_out(self, samp_rate_out):
self.samp_rate_out = samp_rate_out
for channel in self.blocks_resamplers:
self.blocks_resamplers[channel].set_resamp_ratio(self.samp_rate_in / self.samp_rate_out)
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