| #!/usr/bin/env python |
| ################################################## |
| # Gnuradio Python Flow Graph |
| # Title: FCCH Bursts Detector |
| # Author: Piotr Krysik |
| # |
| # Description: Detects positions of FCCH bursts. At the end of each |
| # detected FCCH burst adds to the stream a tag with key "fcch" and value |
| # which is a frequency offset estimate. The input sampling frequency |
| # should be integer multiply of GSM GMKS symbol rate - 1625000/6 Hz. |
| ################################################## |
| |
| from gnuradio import blocks |
| from gnuradio import gr |
| from gnuradio.filter import firdes |
| import grgsm |
| |
| class fcch_detector(grgsm.hier_block): |
| |
| def __init__(self, OSR=4): |
| grgsm.hier_block.__init__( |
| self, "FCCH bursts detector", |
| gr.io_signature(1, 1, gr.sizeof_gr_complex*1), |
| gr.io_signature(1, 1, gr.sizeof_gr_complex*1), |
| ) |
| |
| ################################################## |
| # Parameters |
| ################################################## |
| self.OSR = OSR |
| |
| ################################################## |
| # Variables |
| ################################################## |
| self.f_symb = f_symb = 1625000.0/6.0 |
| self.samp_rate = samp_rate = f_symb*OSR |
| |
| ################################################## |
| # Blocks |
| ################################################## |
| self.gsm_fcch_burst_tagger_0 = grgsm.fcch_burst_tagger(OSR) |
| self.blocks_threshold_ff_0_0 = blocks.threshold_ff(0, 0, 0) |
| self.blocks_threshold_ff_0 = blocks.threshold_ff(int((138)*samp_rate/f_symb), int((138)*samp_rate/f_symb), 0) |
| self.blocks_multiply_conjugate_cc_0 = blocks.multiply_conjugate_cc(1) |
| self.blocks_moving_average_xx_0 = blocks.moving_average_ff(int((142)*samp_rate/f_symb), 1, int(1e6)) |
| self.blocks_delay_0 = blocks.delay(gr.sizeof_gr_complex*1, int(OSR)) |
| self.blocks_complex_to_arg_0 = blocks.complex_to_arg(1) |
| |
| ################################################## |
| # Connections |
| ################################################## |
| self.connect((self, 0), (self.blocks_multiply_conjugate_cc_0, 0)) |
| self.connect((self.blocks_delay_0, 0), (self.blocks_multiply_conjugate_cc_0, 1)) |
| self.connect((self.blocks_complex_to_arg_0, 0), (self.blocks_threshold_ff_0_0, 0)) |
| self.connect((self, 0), (self.blocks_delay_0, 0)) |
| self.connect((self.blocks_multiply_conjugate_cc_0, 0), (self.blocks_complex_to_arg_0, 0)) |
| self.connect((self.blocks_moving_average_xx_0, 0), (self.blocks_threshold_ff_0, 0)) |
| self.connect((self.blocks_threshold_ff_0_0, 0), (self.blocks_moving_average_xx_0, 0)) |
| self.connect((self.gsm_fcch_burst_tagger_0, 0), (self, 0)) |
| self.connect((self, 0), (self.gsm_fcch_burst_tagger_0, 0)) |
| self.connect((self.blocks_threshold_ff_0, 0), (self.gsm_fcch_burst_tagger_0, 1)) |
| |
| def get_OSR(self): |
| return self.OSR |
| |
| def set_OSR(self, OSR): |
| self.OSR = OSR |
| self.set_samp_rate(self.f_symb*self.OSR) |
| self.blocks_delay_0.set_dly(int(self.OSR)) |
| |
| |