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config: use hexagonal grid for better SNR

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Roman Zeyde
2014-09-30 14:05:54 +03:00
parent e7c04e4aa9
commit e94ccdd8de
1 changed files with 8 additions and 8 deletions
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16
amodem/config.py
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@@ -1,8 +1,7 @@
Fs = 32000.0 # sampling frequency [Hz]
Tsym = 0.001 # symbol duration [seconds]
Nfreq = 8 # number of frequencies used
Nx = 8
Ny = 8
Npoints = 64
F0 = 1e3
# Update default configuration from environment variables
@@ -23,12 +22,13 @@ carrier_index = 0
Fc = frequencies[carrier_index]
Tc = 1.0 / Fc
assert Nx == 2 ** round(np.log2(Nx))
assert Ny == 2 ** round(np.log2(Ny))
xs = np.linspace(-1, 1, Nx) if Nx > 1 else [0.0]
ys = np.linspace(-1, 1, Ny) if Ny > 1 else [0.0]
symbols = np.array([complex(x, y) for x in xs for y in ys])
# Hexagonal symbol constellation (optimal "sphere packing")
I = np.arange(-Npoints, Npoints+1)
imag_factor = np.exp(1j * np.pi / 3.0)
offset = 0.5
symbols = [(x + y*imag_factor + offset) for x in I for y in I]
symbols.sort(key=lambda z: (z*z.conjugate()).real)
symbols = np.array(symbols[:Npoints])
symbols = symbols / np.max(np.abs(symbols))
Nsym = int(Tsym / Ts)