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change constellation to real QAM

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This commit is contained in:
Roman Zeyde
2014-07-09 09:17:18 +03:00
parent 2e4718e0fe
commit 3870242580
3 changed files with 23 additions and 16 deletions
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31
sigproc.py
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@@ -24,18 +24,21 @@ def train(S, training):
return lambda x: lfilter(b=[b0, b1], a=[1, -a1], x=x)
class QAM(object):
def __init__(self, bits_per_symbol, radii):
def __init__(self, symbols):
self._enc = {}
index = 0
N = (2 ** bits_per_symbol) / len(radii)
for a in radii:
for i in range(N):
k = tuple(int(index & (1 << j) != 0) for j in range(bits_per_symbol))
v = np.exp(2j * i * np.pi / N)
self._enc[k] = v * a
index += 1
symbols = np.array(list(symbols))
bits_per_symbol = np.log2(len(symbols))
bits_per_symbol = np.round(bits_per_symbol)
N = (2 ** bits_per_symbol)
assert N == len(symbols)
bits_per_symbol = int(bits_per_symbol)
for i, v in enumerate(symbols):
bits = tuple(int(i & (1 << j) != 0) for j in range(bits_per_symbol))
self._enc[bits] = v
self._dec = {v: k for k, v in self._enc.items()}
self.points = self._enc.values()
self.symbols = symbols
self.bits_per_symbol = bits_per_symbol
def encode(self, bits):
@@ -48,10 +51,12 @@ class QAM(object):
def decode(self, symbols):
for s in symbols:
index = np.argmin(np.abs(s - self.points))
yield self._dec[ self.points[index] ]
index = np.argmin(np.abs(s - self.symbols))
yield self._dec[ self.symbols[index] ]
modulator = QAM(bits_per_symbol=4, radii=[1.0, 0.6])
_xs, _ys = np.linspace(-1, 1, 4), np.linspace(-1, 1, 4) # QAM-16
_symbols = np.array([complex(x, y) for x in _xs for y in _ys]) * np.sqrt(0.5)
modulator = QAM(_symbols)
def clip(x, lims):
return min(max(x, lims[0]), lims[1])