#

# GMSK modulation and demodulation.  

#

#

# Copyright 2005,2006 Free Software Foundation, Inc.

# 

# This file is part of GNU Radio

# 

# GNU Radio is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2, or (at your option)

# any later version.

# 

# GNU Radio is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

# 

# You should have received a copy of the GNU General Public License

# along with GNU Radio; see the file COPYING.  If not, write to

# the Free Software Foundation, Inc., 51 Franklin Street,

# Boston, MA 02110-1301, USA.

# 

# See gnuradio-examples/python/digital for examples

from gnuradio import gr

from gnuradio import modulation_utils

from math import pi

import Numeric

from pprint import pprint

import inspect

# default values (used in __init__ and add_options)

_def_samples_per_symbol = 2

_def_bt = 0.35

_def_verbose = False

_def_log = False

_def_gain_mu = 0.05

_def_mu = 0.5

_def_freq_error = 0.0

_def_omega_relative_limit = 0.005

# /////////////////////////////////////////////////////////////////////////////

#                              GMSK modulator

# /////////////////////////////////////////////////////////////////////////////

class gmsk_mod(gr.hier_block2):

    def __init__(self,

                 samples_per_symbol=_def_samples_per_symbol,

                 bt=_def_bt,

                 verbose=_def_verbose,

                 log=_def_log):

        """

        Hierarchical block for Gaussian Minimum Shift Key (GMSK)

        modulation.

        The input is a byte stream (unsigned char) and the

        output is the complex modulated signal at baseband.

        @param samples_per_symbol: samples per baud >= 2

        @type samples_per_symbol: integer

        @param bt: Gaussian filter bandwidth * symbol time

        @type bt: float

        @param verbose: Print information about modulator?

        @type verbose: bool

        @param debug: Print modualtion data to files?

        @type debug: bool       

        """

        gr.hier_block2.__init__(self, "gmsk_mod",

                                gr.io_signature(1,1,gr.sizeof_char),       # Input signature

                                gr.io_signature(1,1,gr.sizeof_gr_complex)) # Output signature

        self._samples_per_symbol = samples_per_symbol

        self._bt = bt

        if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:

            raise TypeError, ("samples_per_symbol must be an integer >= 2, is %r" % (samples_per_symbol,))

        ntaps = 4 * samples_per_symbol                        # up to 3 bits in filter at once

        sensitivity = (pi / 2) / samples_per_symbol        # phase change per bit = pi / 2

        # Turn it into NRZ data.

        self.nrz = gr.bytes_to_syms()

        # Form Gaussian filter

        # Generate Gaussian response (Needs to be convolved with window below).

        self.gaussian_taps = gr.firdes.gaussian(

                1,                       # gain

                samples_per_symbol,    # symbol_rate

                bt,                       # bandwidth * symbol time

                ntaps                       # number of taps

                )

        self.sqwave = (1,) * samples_per_symbol       # rectangular window

        self.taps = Numeric.convolve(Numeric.array(self.gaussian_taps),Numeric.array(self.sqwave))

        self.gaussian_filter = gr.interp_fir_filter_fff(samples_per_symbol, self.taps)

        # FM modulation

        self.fmmod = gr.frequency_modulator_fc(sensitivity)

        # Define components from objects

        self.define_component("nrz", self.nrz)

        self.define_component("gaussian_filter", self.gaussian_filter)

        self.define_component("fmmod", self.fmmod)

        # Connect components

        self.connect("self", 0, "nrz", 0)

        self.connect("nrz", 0, "gaussian_filter", 0)

        self.connect("gaussian_filter", 0, "fmmod", 0)

        self.connect("fmmod", 0, "self", 0)

        if verbose:

            self._print_verbage()

        if log:

            self._setup_logging()

    def samples_per_symbol(self):

        return self._samples_per_symbol

    def bits_per_symbol(self=None):     # staticmethod that's also callable on an instance

        return 1

    bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.

    def _print_verbage(self):

        print "bits per symbol = %d" % self.bits_per_symbol()

        print "Gaussian filter bt = %.2f" % self._bt

    def _setup_logging(self):

        print "Modulation logging turned on."

        self.define_component("nrz_dat", gr.file_sink(gr.sizeof_float, "tx_nrz.dat"))

        self.define_component("gaussian_filter_dat", gr.file_sink(gr.sizeof_float, "tx_gaussian_filter.dat"))

        self.define_component("fmmod_dat", gr.file_sink(gr.sizeof_gr_complex, "tx_fmmod.dat"))

        self.connect("nrz", 0, "nrz_dat", 0)

        self.connect("gaussian_filter", 0, "gaussian_filter_dat", 0)

        self.connect("fmmod", 0, "fmmod_dat", 0)

    def add_options(parser):

        """

        Adds GMSK modulation-specific options to the standard parser

        """

        parser.add_option("", "--bt", type="float", default=_def_bt,

                          help="set bandwidth-time product [default=%default] (GMSK)")

    add_options=staticmethod(add_options)

    def extract_kwargs_from_options(options):

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

        return modulation_utils.extract_kwargs_from_options(gmsk_mod.__init__,

                                                            ('self', 'fg'), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

# /////////////////////////////////////////////////////////////////////////////

#                            GMSK demodulator

# /////////////////////////////////////////////////////////////////////////////

class gmsk_demod(gr.hier_block2):

    def __init__(self,

                 samples_per_symbol=_def_samples_per_symbol,

                 gain_mu=_def_gain_mu,

                 mu=_def_mu,

                 omega_relative_limit=_def_omega_relative_limit,

                 freq_error=_def_freq_error,

                 verbose=_def_verbose,

                 log=_def_log):

        """

        Hierarchical block for Gaussian Minimum Shift Key (GMSK)

        demodulation.

        The input is the complex modulated signal at baseband.

        The output is a stream of bits packed 1 bit per byte (the LSB)

        @param samples_per_symbol: samples per baud

        @type samples_per_symbol: integer

        @param verbose: Print information about modulator?

        @type verbose: bool

        @param log: Print modualtion data to files?

        @type log: bool 

        Clock recovery parameters.  These all have reasonble defaults.

        @param gain_mu: controls rate of mu adjustment

        @type gain_mu: float

        @param mu: fractional delay [0.0, 1.0]

        @type mu: float

        @param omega_relative_limit: sets max variation in omega

        @type omega_relative_limit: float, typically 0.000200 (200 ppm)

        @param freq_error: bit rate error as a fraction

        @param float

        """

        gr.hier_block2.__init__(self, "gmsk_demod",

                                gr.io_signature(1,1,gr.sizeof_gr_complex), # Input signature

                                gr.io_signature(1,1,gr.sizeof_char))       # Output signature

        self._samples_per_symbol = samples_per_symbol

        self._gain_mu = gain_mu

        self._mu = mu

        self._omega_relative_limit = omega_relative_limit

        self._freq_error = freq_error

        if samples_per_symbol < 2:

            raise TypeError, "samples_per_symbol >= 2, is %f" % samples_per_symbol

        self._omega = samples_per_symbol*(1+self._freq_error)

        self._gain_omega = .25 * self._gain_mu * self._gain_mu        # critically damped

        # Demodulate FM

        sensitivity = (pi / 2) / samples_per_symbol

        self.fmdemod = gr.quadrature_demod_cf(1.0 / sensitivity)

        # the clock recovery block tracks the symbol clock and resamples as needed.

        # the output of the block is a stream of soft symbols (float)

        self.clock_recovery = gr.clock_recovery_mm_ff(self._omega, self._gain_omega,

                                                      self._mu, self._gain_mu,

                                                      self._omega_relative_limit)

        # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample

        self.slicer = gr.binary_slicer_fb()

        # Define components from objects

        self.define_component("fmdemod", self.fmdemod)

        self.define_component("clock_recovery", self.clock_recovery)

        self.define_component("slicer", self.slicer)

        # Connect components

        self.connect("self", 0, "fmdemod", 0)

        self.connect("fmdemod", 0, "clock_recovery", 0)

        self.connect("clock_recovery", 0, "slicer", 0)

        self.connect("slicer", 0, "self", 0)

        if verbose:

            self._print_verbage()

        if log:

            self._setup_logging()

    def samples_per_symbol(self):

        return self._samples_per_symbol

    def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance

        return 1

    bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.

    def _print_verbage(self):

        print "bits per symbol = %d" % self.bits_per_symbol()

        print "M&M clock recovery omega = %f" % self._omega

        print "M&M clock recovery gain mu = %f" % self._gain_mu

        print "M&M clock recovery mu = %f" % self._mu

        print "M&M clock recovery omega rel. limit = %f" % self._omega_relative_limit

        print "frequency error = %f" % self._freq_error

    def _setup_logging(self):

        print "Demodulation logging turned on."

        self.define_component("fmdemod_dat", gr.file_sink(gr.sizeof_float, "rx_fmdemod.dat"))

        self.define_component("clock_recovery_dat", gr.file_sink(gr.sizeof_float, "rx_clock_recovery.dat"))

        self.define_component("slicer_dat", gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))

        self.connect("fmdemod", 0, "fmdemod_dat", 0)

        self.connect("clock_recovery", 0, "clock_recovery_dat", 0)

        self.connect("slicer", 0, "slicer_dat", 0)

    def add_options(parser):

        """

        Adds GMSK demodulation-specific options to the standard parser

        """

        parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,

                          help="M&M clock recovery gain mu [default=%default] (GMSK/PSK)")

        parser.add_option("", "--mu", type="float", default=_def_mu,

                          help="M&M clock recovery mu [default=%default] (GMSK/PSK)")

        parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,

                          help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")

        parser.add_option("", "--freq-error", type="float", default=_def_freq_error,

                          help="M&M clock recovery frequency error [default=%default] (GMSK)")

    add_options=staticmethod(add_options)

    def extract_kwargs_from_options(options):

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

        return modulation_utils.extract_kwargs_from_options(gmsk_demod.__init__,

                                                            ('self', 'fg'), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

#

# Add these to the mod/demod registry

#

modulation_utils.add_type_1_mod('gmsk', gmsk_mod)

modulation_utils.add_type_1_demod('gmsk', gmsk_demod)