def make_non_differential_constellation(m, gray_coded): side = int(pow(m, 0.5)) if (not isinstance(m, int) or m < 4 or not is_power_of_four(m)): raise ValueError("m must be a power of 4 integer.") # Each symbol holds k bits. k = int(log(m) / log(2.0)) if gray_coded: # Number rows and columns using gray codes. gcs = gray_code(side) # Get inverse gray codes. i_gcs = mod_codes.invert_code(gcs) else: i_gcs = range(0, side) # The distance between points is found. step = 2.0/(side-1) gc_to_x = [-1 + i_gcs[gc]*step for gc in range(0, side)] # First k/2 bits determine x position. # Following k/2 bits determine y position. const_map = [] for i in range(m): y = gc_to_x[get_bits(i, 0, k/2)] x = gc_to_x[get_bits(i, k/2, k/2)] const_map.append(complex(x,y)) return const_map
def psk_constellation(m=_def_constellation_points, mod_code=_def_mod_code): """ Creates a PSK constellation object. """ k = log(m) / log(2.0) if (k != int(k)): raise StandardError('Number of constellation points must be a power of two.') points = [exp(2*pi*(0+1j)*i/m) for i in range(0,m)] pre_diff_code, post_diff_code = create_encodings(mod_code, m) if post_diff_code is not None: inverse_post_diff_code = mod_codes.invert_code(post_diff_code) points = [points[x] for x in inverse_post_diff_code] constellation = digital.constellation_psk(points, pre_diff_code, m) return constellation
def __init__(self, constellation, samples_per_symbol=_def_samples_per_symbol, differential=_def_differential, excess_bw=_def_excess_bw, gray_coded=True, freq_bw=_def_freq_bw, timing_bw=_def_timing_bw, phase_bw=_def_phase_bw, verbose=_def_verbose, log=_def_log): """ Hierarchical block for RRC-filtered differential generic demodulation. The input is the complex modulated signal at baseband. The output is a stream of bits packed 1 bit per byte (LSB) @param constellation: determines the modulation type @type constellation: gnuradio.digital.gr_constellation @param samples_per_symbol: samples per symbol >= 2 @type samples_per_symbol: float @param excess_bw: Root-raised cosine filter excess bandwidth @type excess_bw: float @param gray_coded: turn gray coding on/off @type gray_coded: bool @param freq_bw: loop filter lock-in bandwidth @type freq_bw: float @param timing_bw: timing recovery loop lock-in bandwidth @type timing_bw: float @param phase_bw: phase recovery loop bandwidth @type phase_bw: 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, "generic_demod", gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature gr.io_signature(1, 1, gr.sizeof_char)) # Output signature self._constellation = constellation.base() self._samples_per_symbol = samples_per_symbol self._excess_bw = excess_bw self._phase_bw = phase_bw self._freq_bw = freq_bw self._timing_bw = timing_bw self._timing_max_dev= _def_timing_max_dev self._differential = differential if self._samples_per_symbol < 2: raise TypeError, ("sbp must be >= 2, is %d" % self._samples_per_symbol) arity = pow(2,self.bits_per_symbol()) nfilts = 32 ntaps = 11 * int(self._samples_per_symbol*nfilts) # Automatic gain control self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100) # Frequency correction fll_ntaps = 55 self.freq_recov = digital.fll_band_edge_cc(self._samples_per_symbol, self._excess_bw, fll_ntaps, self._freq_bw) # symbol timing recovery with RRC data filter taps = gr.firdes.root_raised_cosine(nfilts, nfilts*self._samples_per_symbol, 1.0, self._excess_bw, ntaps) self.time_recov = digital.pfb_clock_sync_ccf(self._samples_per_symbol, self._timing_bw, taps, nfilts, nfilts//2, self._timing_max_dev) fmin = -0.25 fmax = 0.25 self.receiver = digital.constellation_receiver_cb( self._constellation, self._phase_bw, fmin, fmax) # Do differential decoding based on phase change of symbols if differential: self.diffdec = digital.diff_decoder_bb(arity) if gray_coded: self.symbol_mapper = digital.map_bb( mod_codes.invert_code(self._constellation.pre_diff_code())) # unpack the k bit vector into a stream of bits self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol()) if verbose: self._print_verbage() if log: self._setup_logging() # Connect and Initialize base class blocks = [self, self.agc, self.freq_recov, self.time_recov, self.receiver] if differential: blocks.append(self.diffdec) if self._constellation.apply_pre_diff_code(): blocks.append(self.symbol_mapper) blocks += [self.unpack, self] self.connect(*blocks)