diff options
Diffstat (limited to 'gnuradio-core/src/python/gnuradio/blks2impl/qam.py')
| -rw-r--r-- | gnuradio-core/src/python/gnuradio/blks2impl/qam.py | 92 |
1 files changed, 74 insertions, 18 deletions
diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/qam.py b/gnuradio-core/src/python/gnuradio/blks2impl/qam.py index b6096d2cb9..220a3f62f5 100644 --- a/gnuradio-core/src/python/gnuradio/blks2impl/qam.py +++ b/gnuradio-core/src/python/gnuradio/blks2impl/qam.py @@ -25,12 +25,17 @@ QAM modulation and demodulation. from math import pi, sqrt, log -from gnuradio import gr, gru, modulation_utils2 +from gnuradio import gr, modulation_utils2 from gnuradio.blks2impl.generic_mod_demod import generic_mod, generic_demod from gnuradio.utils.gray_code import gray_code # Default number of points in constellation. _def_constellation_points = 16 +# Whether the quadrant bits are coded differentially. +_def_differential = True +# Whether gray coding is used. If differential is True then gray +# coding is used within but not between each quadrant. +_def_gray_coded = True def is_power_of_four(x): v = log(x)/log(4) @@ -47,13 +52,16 @@ def get_bits(x, n, k): # Remove all bits bigger than n+k-1 return v % pow(2, k) -def make_constellation(m): +def make_differential_constellation(m, gray_coded=_def_gray_coded): """ Create a constellation with m possible symbols where m must be a power of 4. Points are laid out in a square grid. + Bits referring to the quadrant are differentilly encoded, + remaining bits are gray coded. + """ sqrtm = pow(m, 0.5) if (not isinstance(m, int) or m < 4 or not is_power_of_four(m)): @@ -63,10 +71,13 @@ def make_constellation(m): # First create a constellation for one quadrant containing m/4 points. # The quadrant has 'side' points along each side of a quadrant. side = int(sqrtm/2) - # Number rows and columns using gray codes. - gcs = gray_code(side) - # Get inverse gray codes. - i_gcs = dict([(v, key) for key, v in enumerate(gcs)]) + if gray_coded: + # Number rows and columns using gray codes. + gcs = gray_code(side) + # Get inverse gray codes. + i_gcs = dict([(v, key) for key, v in enumerate(gcs)]) + else: + i_gcs = dict([(i, i) for i in range(0, side)]) # The distance between points is found. step = 1/(side-0.5) @@ -100,19 +111,51 @@ def make_constellation(m): return const_map +def make_not_differential_constellation(m, gray_coded=_def_gray_coded): + side = 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 = dict([(v, key) for key, v in enumerate(gcs)]) + else: + i_gcs = dict([(i, i) for i in range(0, m)]) + # The distance between points is found. + step = 2/(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 # ///////////////////////////////////////////////////////////////////////////// # QAM constellation # ///////////////////////////////////////////////////////////////////////////// -def qam_constellation(constellation_points=_def_constellation_points): +def qam_constellation(constellation_points=_def_constellation_points, + differential=_def_differential, + gray_coded=_def_gray_coded,): """ Creates a QAM constellation object. """ - points = make_constellation(constellation_points) + if differential: + points = make_differential_constellation(constellation_points, gray_coded) + else: + points = make_not_differential_constellation(constellation_points, gray_coded) side = int(sqrt(constellation_points)) width = 2.0/(side-1) - constellation = gr.constellation_sector(points, side, side, width, width) + constellation = gr.constellation_rect(points, side, side, width, width) return constellation # ///////////////////////////////////////////////////////////////////////////// @@ -121,7 +164,10 @@ def qam_constellation(constellation_points=_def_constellation_points): class qam_mod(generic_mod): - def __init__(self, constellation_points=_def_constellation_points, *args, **kwargs): + def __init__(self, constellation_points=_def_constellation_points, + differential=_def_differential, + gray_coded=_def_gray_coded, + *args, **kwargs): """ Hierarchical block for RRC-filtered QAM modulation. @@ -132,10 +178,11 @@ class qam_mod(generic_mod): See generic_mod block for list of parameters. """ - if not isinstance(constellation_points, int) or not is_power_of_four(constellation_points): - raise ValueError("number of constellation points must be a power of four.") - constellation = qam_constellation(constellation_points) - super(qam_mod, self).__init__(constellation, *args, **kwargs) + constellation = qam_constellation(constellation_points, differential, gray_coded) + # We take care of the gray coding in the constellation generation so it doesn't + # need to be done in the block. + super(qam_mod, self).__init__(constellation, differential=differential, + gray_coded=False, *args, **kwargs) # ///////////////////////////////////////////////////////////////////////////// # QAM demodulator @@ -144,7 +191,10 @@ class qam_mod(generic_mod): class qam_demod(generic_demod): - def __init__(self, constellation_points=_def_constellation_points, *args, **kwargs): + def __init__(self, constellation_points=_def_constellation_points, + differential=_def_differential, + gray_coded=_def_gray_coded, + *args, **kwargs): """ Hierarchical block for RRC-filtered QAM modulation. @@ -154,12 +204,18 @@ class qam_demod(generic_demod): See generic_demod block for list of parameters. """ - - constellation = qam_constellation(constellation_points) - super(qam_demod, self).__init__(constellation, *args, **kwargs) + print(args) + print(kwargs) + constellation = qam_constellation(constellation_points, differential, gray_coded) + # We take care of the gray coding in the constellation generation so it doesn't + # need to be done in the block. + super(qam_demod, self).__init__(constellation, differential=differential, + gray_coded=False, + *args, **kwargs) # # Add these to the mod/demod registry # modulation_utils2.add_type_1_mod('qam', qam_mod) modulation_utils2.add_type_1_demod('qam', qam_demod) +modulation_utils2.add_type_1_constellation('qam', qam_constellation) |