diff options
Diffstat (limited to 'gr-digital/python/qam.py')
| -rw-r--r-- | gr-digital/python/qam.py | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/gr-digital/python/qam.py b/gr-digital/python/qam.py index 5b1f7683b8..73bad2f75b 100644 --- a/gr-digital/python/qam.py +++ b/gr-digital/python/qam.py @@ -30,7 +30,7 @@ from generic_mod_demod import generic_mod, generic_demod from utils.gray_code import gray_code from utils import mod_codes import modulation_utils -import digital_swig +import digital_swig as digital # Default number of points in constellation. _def_constellation_points = 16 @@ -157,16 +157,22 @@ def qam_constellation(constellation_points=_def_constellation_points, else: raise ValueError("Mod code is not implemented for QAM") if differential: - points = make_differential_constellation(constellation_points, gray_coded) + points = make_differential_constellation(constellation_points, gray_coded=False) else: points = make_non_differential_constellation(constellation_points, gray_coded) side = int(sqrt(constellation_points)) width = 2.0/(side-1) - # No pre-diff code - # Should add one so that we can gray-code the quadrant bits too. - pre_diff_code = [] - constellation = digital_swig.constellation_rect(points, pre_diff_code, 4, - side, side, width, width) + # For differential and gray-coded then gray-code the first two + # bits with a pre_diff_code. + # FIXME: It would be good to have a test to make sure that gray-coded constellations + # are really gray-coded. Perhaps by checking on the correlation between bit-errors. + if differential and gray_coded: + m = constellation_points + pre_diff_code = range(0, m/2) + range(3*m/4, m) + range(m/2, 3*m/4) + else: + pre_diff_code = [] + constellation = digital.constellation_rect(points, pre_diff_code, 4, + side, side, width, width) return constellation # ///////////////////////////////////////////////////////////////////////////// |