From d53109a88522d243bf684ffe1a9aad2801c52f07 Mon Sep 17 00:00:00 2001
From: Tom Rondeau <trondeau@vt.edu>
Date: Wed, 12 Oct 2011 22:42:55 -0400
Subject: digital: OFDM using new psk and qam modules for constellations. Also,
psk2->psk updated in all files and examples.
---
gr-digital/python/psk.py | 174 +++++++++++++++++++++++++++--------------------
1 file changed, 101 insertions(+), 73 deletions(-)
(limited to 'gr-digital/python/psk.py')
diff --git a/gr-digital/python/psk.py b/gr-digital/python/psk.py
index acedf3b69a..82781e63b0 100644
--- a/gr-digital/python/psk.py
+++ b/gr-digital/python/psk.py
@@ -1,5 +1,5 @@
#
-# Copyright 2005,2006 Free Software Foundation, Inc.
+# Copyright 2005,2006,2011 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
@@ -19,76 +19,104 @@
# Boston, MA 02110-1301, USA.
#
-from math import pi, sqrt, log10
-import math, cmath
-
-# The following algorithm generates Gray coded constellations for M-PSK for M=[2,4,8]
-def make_gray_constellation(m):
- # number of bits/symbol (log2(M))
- k = int(log10(m) / log10(2.0))
-
- coeff = 1
- const_map = []
- bits = [0]*3
- for i in range(m):
- # get a vector of the k bits to use in this mapping
- bits[3-k:3] = [((i&(0x01 << k-j-1)) >> k-j-1) for j in range(k)]
-
- theta = -(2*bits[0]-1)*(2*pi/m)*(bits[0]+abs(bits[1]-bits[2])+2*bits[1])
- re = math.cos(theta)
- im = math.sin(theta)
- const_map.append(complex(re, im)) # plug it into the constellation
+"""
+PSK modulation and demodulation.
+"""
+
+from math import pi, log
+from cmath import exp
+
+import digital_swig
+import modulation_utils2
+from utils import mod_codes, gray_code
+from generic_mod_demod import generic_mod, generic_demod
+
+# Default number of points in constellation.
+_def_constellation_points = 4
+# The default encoding (e.g. gray-code, set-partition)
+_def_mod_code = mod_codes.GRAY_CODE
+
+def create_encodings(mod_code, arity):
+ 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)
+ elif mod_code == mod_codes.NO_CODE:
+ pre_diff_code = []
+ else:
+ raise ValueError('That modulation code is not implemented for this constellation.')
+ return (pre_diff_code, post_diff_code)
- # return the constellation; by default, it is normalized
- return const_map
-
-# This makes a constellation that increments around the unit circle
-def make_constellation(m):
- return [cmath.exp(i * 2 * pi / m * 1j) for i in range(m)]
-
-# Common definition of constellations for Tx and Rx
-constellation = {
- 2 : make_constellation(2), # BPSK
- 4 : make_constellation(4), # QPSK
- 8 : make_constellation(8) # 8PSK
- }
-
-gray_constellation = {
- 2 : make_gray_constellation(2), # BPSK
- 4 : make_gray_constellation(4), # QPSK
- 8 : make_gray_constellation(8) # 8PSK
- }
-
-# -----------------------
-# Do Gray code
-# -----------------------
-# binary to gray coding -- constellation does Gray coding
-binary_to_gray = {
- 2 : range(2),
- 4 : [0,1,3,2],
- 8 : [0, 1, 3, 2, 7, 6, 4, 5]
- }
-
-# gray to binary
-gray_to_binary = {
- 2 : range(2),
- 4 : [0,1,3,2],
- 8 : [0, 1, 3, 2, 6, 7, 5, 4]
- }
-
-# -----------------------
-# Don't Gray code
-# -----------------------
-# identity mapping
-binary_to_ungray = {
- 2 : range(2),
- 4 : range(4),
- 8 : range(8)
- }
-
-# identity mapping
-ungray_to_binary = {
- 2 : range(2),
- 4 : range(4),
- 8 : range(8)
- }
+# /////////////////////////////////////////////////////////////////////////////
+# PSK constellation
+# /////////////////////////////////////////////////////////////////////////////
+
+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_swig.constellation_psk(points, pre_diff_code, m)
+ return constellation
+
+# /////////////////////////////////////////////////////////////////////////////
+# PSK modulator
+# /////////////////////////////////////////////////////////////////////////////
+
+class psk_mod(generic_mod):
+
+ def __init__(self, constellation_points=_def_constellation_points,
+ mod_code=_def_mod_code,
+ *args, **kwargs):
+
+ """
+ Hierarchical block for RRC-filtered PSK modulation.
+
+ The input is a byte stream (unsigned char) and the
+ output is the complex modulated signal at baseband.
+
+ See generic_mod block for list of parameters.
+ """
+
+ constellation = psk_constellation(constellation_points, mod_code)
+ super(psk_mod, self).__init__(constellation, *args, **kwargs)
+
+# /////////////////////////////////////////////////////////////////////////////
+# PSK demodulator
+#
+# /////////////////////////////////////////////////////////////////////////////
+
+class psk_demod(generic_demod):
+
+ def __init__(self, constellation_points=_def_constellation_points,
+ mod_code=_def_mod_code,
+ *args, **kwargs):
+
+ """
+ Hierarchical block for RRC-filtered PSK modulation.
+
+ The input is a byte stream (unsigned char) and the
+ output is the complex modulated signal at baseband.
+
+ See generic_demod block for list of parameters.
+ """
+
+ constellation = psk_constellation(constellation_points, mod_code)
+ super(psk_demod, self).__init__(constellation, *args, **kwargs)
+
+#
+# Add these to the mod/demod registry
+#
+modulation_utils2.add_type_1_mod('psk', psk_mod)
+modulation_utils2.add_type_1_demod('psk', psk_demod)
+modulation_utils2.add_type_1_constellation('psk', psk_constellation)
--
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