[Commit-gnuradio] r8222 - gnuradio/trunk/gnuradio-core/src/python/gnuradio/blks2impl

[trondeau]

Author: trondeau
Date: 2008-04-18 10:06:40 -0600 (Fri, 18 Apr 2008)
New Revision: 8222

Modified:
   gnuradio/trunk/gnuradio-core/src/python/gnuradio/blks2impl/ofdm_sync_ml.py
Log:
Improved performance of the ML sync (with added computations). It uses the 
energy calculation to normalize the correlation and the timing sequence and 
correlation together to determine the timing. This works for frequencies of 
+-0.6 offset, which is a limiting factor still in the performance but better 
than the previous checkin.

Modified: 
gnuradio/trunk/gnuradio-core/src/python/gnuradio/blks2impl/ofdm_sync_ml.py
===================================================================
--- gnuradio/trunk/gnuradio-core/src/python/gnuradio/blks2impl/ofdm_sync_ml.py  
2008-04-18 00:38:56 UTC (rev 8221)
+++ gnuradio/trunk/gnuradio-core/src/python/gnuradio/blks2impl/ofdm_sync_ml.py  
2008-04-18 16:06:40 UTC (rev 8222)
@@ -98,7 +98,7 @@
         self.connect(self.diff, self.pk_detect)
 
         # The DPLL corrects for timing differences between CP correlations
-        use_dpll = 1
+        use_dpll = 0
         if use_dpll:
             self.dpll = gr.dpll_bb(float(symbol_length),0.01)
             self.connect(self.pk_detect, self.dpll)
@@ -117,21 +117,29 @@
         kstime.reverse()
         self.kscorr = gr.fir_filter_ccc(1, kstime)
         self.corrmag = gr.complex_to_mag_squared()
+        self.div = gr.divide_ff()
 
         # The output signature of the correlation has a few spikes because the 
rest of the
         # system uses the repeated preamble symbol. It needs to work that 
generically if 
-        # anyone wants to use this against a WiMAX-like signal since it, too, 
repeats
-        # This slicing against a threshold will __not__ work over the air 
unless the 
-        # received power is at just the right point. It __does__ work under 
the normal
-        # conditions of the loopback model.
-        self.slice = gr.threshold_ff(700000, 700000, 0)
+        # anyone wants to use this against a WiMAX-like signal since it, too, 
repeats.
+        # The output theta of the correlator above is multiplied with this 
correlation to
+        # identify the proper peak and remove other products in this 
cross-correlation
+        self.threshold_factor = 0.1
+        self.slice = gr.threshold_ff(self.threshold_factor, 
self.threshold_factor, 0)
         self.f2b = gr.float_to_char()
+        self.b2f = gr.char_to_float()
+        self.mul = gr.multiply_ff()
         
-        self.connect(self.input, self.kscorr, self.corrmag, self.slice)
-        self.connect(self.kscorr, gr.file_sink(gr.sizeof_gr_complex, 
"kscorr.dat"))
-        self.connect(self.corrmag, gr.file_sink(gr.sizeof_float, 
"kscorrmag.dat"))
-        self.connect(self.slice, gr.file_sink(gr.sizeof_float, "kspeak.dat"))
-
+        # Normalize the power of the corr output by the energy. This is not 
really needed
+        # and could be removed for performance, but it makes for a cleaner 
signal.
+        # if this is removed, the threshold value needs adjustment.
+        self.connect(self.input, self.kscorr, self.corrmag, (self.div,0))
+        self.connect(self.moving_sum_filter, (self.div,1))
+        
+        self.connect(self.div, (self.mul,0))
+        self.connect(self.pk_detect, self.b2f, (self.mul,1))
+        self.connect(self.mul, self.slice)
+        
         # Set output signals
         #    Output 0: fine frequency correction value
         #    Output 1: timing signal
@@ -140,8 +148,14 @@
 
 
         if logging:
+            self.connect(self.moving_sum_filter, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-energy_f.dat"))
             self.connect(self.diff, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-theta_f.dat"))
             self.connect(self.angle, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-epsilon_f.dat"))
+            self.connect(self.corrmag, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-corrmag_f.dat"))
+            self.connect(self.kscorr, gr.file_sink(gr.sizeof_gr_complex, 
"ofdm_sync_ml-kscorr_c.dat"))
+            self.connect(self.div, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-div_f.dat"))
+            self.connect(self.mul, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-mul_f.dat"))
+            self.connect(self.slice, gr.file_sink(gr.sizeof_float, 
"ofdm_sync_ml-slice_f.dat"))
             self.connect(self.pk_detect, gr.file_sink(gr.sizeof_char, 
"ofdm_sync_ml-peaks_b.dat"))
             if use_dpll:
                 self.connect(self.dpll, gr.file_sink(gr.sizeof_char, 
"ofdm_sync_ml-dpll_b.dat"))