From 084249788afd57ffa5e56e699f25cc0e2d6f5616 Mon Sep 17 00:00:00 2001
From: Ben Reynwar <ben@reynwar.net>
Date: Thu, 26 Apr 2012 22:57:05 -0700
Subject: gr-digital: PSK modulation. Gray-coding done by constellation order
for non-differential modulation.
---
gr-digital/python/psk.py | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
(limited to 'gr-digital/python/psk.py')
diff --git a/gr-digital/python/psk.py b/gr-digital/python/psk.py
index 58f6787f0c..4b35447278 100644
--- a/gr-digital/python/psk.py
+++ b/gr-digital/python/psk.py
@@ -35,17 +35,23 @@ from generic_mod_demod import generic_mod, generic_demod
_def_constellation_points = 4
# The default encoding (e.g. gray-code, set-partition)
_def_mod_code = mod_codes.GRAY_CODE
+# Default use of differential encoding
+_def_differential = True
-def create_encodings(mod_code, arity):
+def create_encodings(mod_code, arity, differential):
post_diff_code = None
if mod_code not in mod_codes.codes:
raise ValueError('That modulation code does not exist.')
if mod_code == mod_codes.GRAY_CODE:
- pre_diff_code = gray_code.gray_code(arity)
- elif mod_code == mod_codes.SET_PARTITION_CODE:
- pre_diff_code = set_partition_code.set_partition_code(arity)
+ if differential:
+ pre_diff_code = gray_code.gray_code(arity)
+ post_diff_code = None
+ else:
+ pre_diff_code = []
+ post_diff_code = gray_code.gray_code(arity)
elif mod_code == mod_codes.NO_CODE:
pre_diff_code = []
+ post_diff_code = None
else:
raise ValueError('That modulation code is not implemented for this constellation.')
return (pre_diff_code, post_diff_code)
@@ -54,7 +60,8 @@ def create_encodings(mod_code, arity):
# PSK constellation
# /////////////////////////////////////////////////////////////////////////////
-def psk_constellation(m=_def_constellation_points, mod_code=_def_mod_code):
+def psk_constellation(m=_def_constellation_points, mod_code=_def_mod_code,
+ differential=_def_differential):
"""
Creates a PSK constellation object.
"""
@@ -62,7 +69,7 @@ def psk_constellation(m=_def_constellation_points, mod_code=_def_mod_code):
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)
+ pre_diff_code, post_diff_code = create_encodings(mod_code, m, differential)
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]
@@ -77,6 +84,7 @@ class psk_mod(generic_mod):
def __init__(self, constellation_points=_def_constellation_points,
mod_code=_def_mod_code,
+ differential=_def_differential,
*args, **kwargs):
"""
@@ -88,8 +96,8 @@ class psk_mod(generic_mod):
See generic_mod block for list of parameters.
"""
- constellation = psk_constellation(constellation_points, mod_code)
- super(psk_mod, self).__init__(constellation, *args, **kwargs)
+ constellation = psk_constellation(constellation_points, mod_code, differential)
+ super(psk_mod, self).__init__(constellation, differential, *args, **kwargs)
# /////////////////////////////////////////////////////////////////////////////
# PSK demodulator
@@ -100,6 +108,7 @@ class psk_demod(generic_demod):
def __init__(self, constellation_points=_def_constellation_points,
mod_code=_def_mod_code,
+ differential=_def_differential,
*args, **kwargs):
"""
@@ -111,8 +120,8 @@ class psk_demod(generic_demod):
See generic_demod block for list of parameters.
"""
- constellation = psk_constellation(constellation_points, mod_code)
- super(psk_demod, self).__init__(constellation, *args, **kwargs)
+ constellation = psk_constellation(constellation_points, mod_code, differential)
+ super(psk_demod, self).__init__(constellation, differential, *args, **kwargs)
#
# Add these to the mod/demod registry
--
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