Fix Travis error for #102 & Modulation tests

Author: BastienTr

commpy/modulation.py

@@ -72,7 +72,7 @@ def __init__(self, constellation, reorder_as_gray=True):
             m = log2(len(constellation))
             gray_code_sequence = GrayCode(m).generate_gray()
             gray_code_sequence_array = fromiter((int(g, 2) for g in gray_code_sequence), int, len(constellation))
-            self.constellation = constellation[gray_code_sequence_array.argsort()]
+            self.constellation = array(constellation)[gray_code_sequence_array.argsort()]
         else:
             self.constellation = constellation
 

commpy/tests/test_modulation.py

@@ -3,16 +3,21 @@
 
 from itertools import product
 
-from numpy import zeros, identity, arange, concatenate, log2, array, inf
+from numpy import zeros, identity, arange, concatenate, log2, log10, array, inf, sqrt, sin, pi
 from numpy.random import seed
 from numpy.testing import run_module_suite, assert_allclose, dec, assert_raises, assert_array_equal
+from scipy.special import erf
 
-from commpy.channels import MIMOFlatChannel
+from commpy.channels import MIMOFlatChannel, SISOFlatChannel
 from commpy.links import *
 from commpy.modulation import QAMModem, mimo_ml, bit_lvl_repr, max_log_approx, PSKModem, Modem
 from commpy.utilities import signal_power
 
 
+def Qfunc(x):
+    return 0.5 - 0.5 * erf(x / sqrt(2))
+
+
 @dec.slow
 def test_bit_lvl_repr():
     # Set seed
@@ -124,8 +129,33 @@ def do_custom(self, modem):
         pass
 
 
+@dec.slow
 class TestModulateHardDemodulate(ModemTestcase):
 
+    @staticmethod
+    def check_BER(modem, EbN0dB, BERs_expected):
+        seed(8071996)
+        model = LinkModel(modem.modulate,
+                          SISOFlatChannel(fading_param=(1 + 0j, 0)),
+                          lambda y, _, __, ___: modem.demodulate(y, 'hard'),
+                          modem.num_bits_symbol, modem.constellation, modem.Es)
+        BERs = model.link_performance(EbN0dB + 10 * log10(log2(modem.m)), 5e5, 400, 720)
+        assert_allclose(BERs, BERs_expected, atol=1e-4, rtol=.1,
+                        err_msg='Wrong BER for {}-PSK modulation'.format(modem.m))
+
+    def do_qam(self, modem):
+        EbN0dB = arange(8, 25, 4)
+        nb_pam = sqrt(modem.m)
+        BERs_expected = 2 * (1 - 1 / nb_pam) / log2(nb_pam) * \
+                        Qfunc(sqrt(3 * log2(nb_pam) / (nb_pam ** 2 - 1) * (2 * 10 ** (EbN0dB / 10))))
+        self.check_BER(modem, EbN0dB, BERs_expected)
+
+    def do_psk(self, modem):
+        EbN0dB = arange(15, 25, 4)
+        SERs_expected = 2 * Qfunc(sqrt(2 * modem.num_bits_symbol * 10 ** (EbN0dB / 10)) * sin(pi / modem.m))
+        BERs_expected = SERs_expected / modem.num_bits_symbol
+        self.check_BER(modem, EbN0dB, BERs_expected)
+
     def do(self, modem):
         for bits in product(*((0, 1),) * modem.num_bits_symbol):
             assert_array_equal(bits, modem.demodulate(modem.modulate(bits), 'hard'),