diff options
Diffstat (limited to 'gr-digital/python/qam.py')
| -rw-r--r-- | gr-digital/python/qam.py | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/gr-digital/python/qam.py b/gr-digital/python/qam.py index 5b1f7683b8..0635fda75e 100644 --- a/gr-digital/python/qam.py +++ b/gr-digital/python/qam.py @@ -157,14 +157,20 @@ 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 = [] + # 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_swig.constellation_rect(points, pre_diff_code, 4, side, side, width, width) return constellation |