Make correlate_with_ref an module

1 files changed, 108 insertions, 101 deletions

diff --git a/correlate_with_ref.py b/correlate_with_ref.py
index cb3f7aa..0199730 100755
--- a/correlate_with_ref.py
+++ b/correlate_with_ref.py
@@ -8,113 +8,120 @@ import numpy as np
 import matplotlib.pyplot as pp
 import sys
 
-if len(sys.argv) < 2:
-    print("Usage")
-    print(" script [fc64|u8] <filename> [<figure filename>]")
-    print(" fc64: file is 32-bit float I + 32-bit float Q")
-    print(" u8:   file is 8-bit unsigned I + 8-bit unsigned Q")
-    print(" if <figure filename> is given, save the figure instead of showing it")
-    sys.exit(1)
-
-print("Reading file")
-
-file_in = sys.argv[2]
-
-if sys.argv[1] == "u8":
-    channel_out1 = np.fromfile(file_in, np.uint8)
-    print("Convert u8 IQ to fc64 IQ")
-    channel_out2 = channel_out1.reshape(2, int(len(channel_out1)/2))
-    channel_out3 = channel_out2[0,...] + 1j * channel_out2[1,...]
-    channel_out = channel_out3.astype(np.complex64) / 256.0 - (0.5+0.5j)
-elif sys.argv[1] == "fc64":
-    channel_out = np.fromfile(file_in, np.complex64)
-
-file_figure = None
-if len(sys.argv) == 4:
-    file_figure = sys.argv[3]
-
-print("  File contains {} samples ({}ms)".format(
-    len(channel_out), len(channel_out) / 2048000.0))
-
 # T = 1/2048000 s
 # NULL symbol is 2656 T (about 1.3ms) long.
 T_NULL = 2656
 # Full transmission frame in TM1 is 96ms = 196608 T.
 T_TF = 196608
 
-print("Reading phase reference")
-phase_ref = np.fromfile("phasereference.2048000.fc64.iq", np.complex64)
-
-def calc_cir(channel, start_ix):
-    """Calculate correlation with phase reference"""
-
-    channel_out
-
-
-    # As we do not want to correlate of the whole recording that might be
-    # containing several transmission frames, we first look for the null symbol in the
-    # first 96ms
-    print("Searching for NULL symbol")
-
-    # Calculate power on blocks of length 2656 over the first 96ms. To gain speed,
-    # we move the blocks by N samples.
-    N = 20
-    channel_out_power = np.array([np.abs(channel[start_ix+t:start_ix+t+T_NULL]).sum() for t in range(0, T_TF-T_NULL, N)])
-
-    # Look where the power is smallest, this gives the index where the NULL starts.
-    # Because if the subsampling, we need to multiply the index.
-    t_null = N * channel_out_power.argmin()
-
-    print("  NULL symbol starts at ix={}".format(t_null))
-
-    # The synchronisation channel occupies 5208 T and contains NULL symbol and
-    # phase reference symbol. The phase reference symbol is 5208 - 2656 = 2552 T
-    # long.
-    if len(phase_ref) != 2552:
-        print("Warning: phase ref len is {} != 2552".format(len(phase_ref)))
-
-
-    # We want to correlate our known phase reference symbol against the received
-    # signal, and give us some more margin about the exact position of the NULL
-    # symbol.
-    print("Correlating")
-
-    # We start a bit earlier than the end of the null symbol
-    corr_start_ix = t_null + T_NULL - 50
-
-    # In TM1, the longest spacing between carrier components one can allow is
-    # around 504 T (246us, or 74km at speed of light). This gives us a limit
-    # on the number of correlations it makes sense to do.
-    max_component_delay = 1000 # T
-
-    cir = np.array([np.abs(np.corrcoef(channel[start_ix + corr_start_ix + i:start_ix + corr_start_ix + phase_ref.size + i], phase_ref)[0,1]) for i in range(max_component_delay)])
-
-    # In order to be able to compare measurements accross transmission frames,
-    # we normalise the CIR against channel power
-    channel_power = np.abs(channel[start_ix:start_ix+T_TF]).sum()
-
-    return cir / channel_power
-
-num_correlations = int(len(channel_out) / T_TF)
-print("Doing {} correlations".format(num_correlations))
-
-cirs = np.array([
-    calc_cir(channel_out, i * T_TF)
-    for i in range(num_correlations) ])
-
-print("Plotting")
-
-pp.subplot(211)
-pp.plot(cirs.sum(axis=0))
-pp.subplot(212)
-pp.imshow(cirs)
-
-print("Done")
-
-if file_figure:
-    pp.savefig(file_figure)
-else:
-    pp.show()
+class CIR_Correlate:
+    def __init__(self, iq_filename, iq_format):
+        """Read phase reference from fixed file and load IQ data from
+        iq_filename. iq_format must be fc64 or u8"""
+        self.phase_ref = np.fromfile("phasereference.2048000.fc64.iq", np.complex64)
 
+        if iq_format == "u8":
+            channel_out1 = np.fromfile(iq_filename, np.uint8)
+            channel_out2 = channel_out1.reshape(2, int(len(channel_out1)/2))
+            channel_out3 = channel_out2[0,...] + 1j * channel_out2[1,...]
+            self.channel_out = channel_out3.astype(np.complex64) / 256.0 - (0.5+0.5j)
+        elif sys.argv[1] == "fc64":
+            self.channel_out = np.fromfile(iq_filename, np.complex64)
+
+        print("  File contains {} samples ({}ms)".format(
+            len(self.channel_out), len(self.channel_out) / 2048000.0))
+
+        # Keep track of where the NULL symbols are located
+        self.null_symbol_ixs = []
+
+    def calc_one_cir_(self, start_ix):
+        """Calculate correlation with phase reference for one start index"""
+
+        channel = self.channel_out
+
+        # As we do not want to correlate of the whole recording that might be
+        # containing several transmission frames, we first look for the null symbol in the
+        # first 96ms
+
+        # Calculate power on blocks of length 2656 over the first 96ms. To gain speed,
+        # we move the blocks by N samples.
+        N = 20
+        channel_out_power = np.array([np.abs(channel[start_ix+t:start_ix+t+T_NULL]).sum() for t in range(0, T_TF-T_NULL, N)])
+
+        # Look where the power is smallest, this gives the index where the NULL starts.
+        # Because if the subsampling, we need to multiply the index.
+        t_null = N * channel_out_power.argmin()
+
+        self.null_symbol_ixs.append(t_null)
+
+        # The synchronisation channel occupies 5208 T and contains NULL symbol and
+        # phase reference symbol. The phase reference symbol is 5208 - 2656 = 2552 T
+        # long.
+        if len(self.phase_ref) != 2552:
+            print("Warning: phase ref len is {} != 2552".format(len(self.phase_ref)))
+
+        # We want to correlate our known phase reference symbol against the received
+        # signal, and give us some more margin about the exact position of the NULL
+        # symbol.
+
+        # We start a bit earlier than the end of the null symbol
+        corr_start_ix = t_null + T_NULL - 50
+
+        # In TM1, the longest spacing between carrier components one can allow is
+        # around 504 T (246us, or 74km at speed of light). This gives us a limit
+        # on the number of correlations it makes sense to do.
+        max_component_delay = 1000 # T
+
+        cir = np.array([np.abs(
+            np.corrcoef(channel[
+                start_ix + corr_start_ix + i:
+                start_ix + corr_start_ix + self.phase_ref.size + i
+                ] , self.phase_ref)[0,1]
+            ) for i in range(max_component_delay)])
+
+        # In order to be able to compare measurements accross transmission frames,
+        # we normalise the CIR against channel power
+        channel_power = np.abs(channel[start_ix:start_ix+T_TF]).sum()
+
+        return cir / channel_power
+
+    def plot(self, plot_file):
+        num_correlations = int(len(self.channel_out) / T_TF)
+
+        cirs = np.array([
+            self.calc_one_cir_(i * T_TF)
+            for i in range(num_correlations) ])
+
+        pp.subplot(211)
+        pp.plot(cirs.sum(axis=0))
+        pp.subplot(212)
+        pp.imshow(cirs)
+
+        if file_figure:
+            pp.savefig(plot_file)
+        else:
+            pp.show()
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage")
+        print(" script [fc64|u8] <filename> [<figure filename>]")
+        print(" fc64: file is 32-bit float I + 32-bit float Q")
+        print(" u8:   file is 8-bit unsigned I + 8-bit unsigned Q")
+        print(" if <figure filename> is given, save the figure instead of showing it")
+        sys.exit(1)
+
+    print("Reading file")
+
+    file_format = sys.argv[1]
+    file_in = sys.argv[2]
+    file_figure = None
+    if len(sys.argv) == 4:
+        file_figure = sys.argv[3]
+
+    cir_corr = CIR_Correlate(file_in, file_format)
+    cir_corr.plot(file_figure)
+    print("Done")