scripts init

scripts/commpy/channelcoding/tests/test_ldpc.py

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+# Authors: Veeresh Taranalli <veeresht@gmail.com>
+# License: BSD 3-Clause
+
+from numpy import array, sqrt, zeros
+from numpy.random import randn
+from numpy.testing import assert_allclose
+from commpy.channelcoding.ldpc import get_ldpc_code_params, ldpc_bp_decode
+from commpy.utilities import hamming_dist
+import os
+
+from nose.plugins.attrib import attr
+
+@attr('slow')
+class TestLDPCCode(object):
+
+    @classmethod
+    def setup_class(cls):
+        dir = os.path.dirname(__file__)
+        ldpc_design_file_1 = os.path.join(dir, '../designs/ldpc/gallager/96.33.964.txt')
+        #ldpc_design_file_1 = "../designs/ldpc/gallager/96.33.964.txt"
+        cls.ldpc_code_params = get_ldpc_code_params(ldpc_design_file_1)
+
+    @classmethod
+    def teardown_class(cls):
+        pass
+
+    def test_ldpc_bp_decode(self):
+        N = 96
+        k = 48
+        rate = 0.5
+        Es = 1.0
+        snr_list = array([2.0, 2.5])
+        niters = 10000000
+        tx_codeword = zeros(N, int)
+        ldpcbp_iters = 100
+
+        fer_array_ref = array([200.0/1000, 200.0/2000])
+        fer_array_test = zeros(len(snr_list))
+
+        for idx, ebno in enumerate(snr_list):
+
+            noise_std = 1/sqrt((10**(ebno/10.0))*rate*2/Es)
+            fer_cnt_bp = 0
+
+            for iter_cnt in range(niters):
+
+                awgn_array = noise_std * randn(N)
+                rx_word = 1-(2*tx_codeword) + awgn_array
+                rx_llrs = 2.0*rx_word/(noise_std**2)
+
+                [dec_word, out_llrs] = ldpc_bp_decode(rx_llrs, self.ldpc_code_params, 'SPA',
+                                                      ldpcbp_iters)
+
+                num_bit_errors = hamming_dist(tx_codeword, dec_word)
+                if num_bit_errors > 0:
+                    fer_cnt_bp += 1
+
+                if fer_cnt_bp >= 200:
+                    fer_array_test[idx] = float(fer_cnt_bp)/(iter_cnt+1)
+                    break
+
+        assert_allclose(fer_array_test, fer_array_ref, rtol=2e-1, atol=0)