digital: Updated corr_est

- Works with arbitrary scaling - Summing correlation over two consecutive symbols because the correlation power is spread out when the timing is off. - Changing from a parabolic interpolation to a linear interpolation measurement for the timing offset. Providing a linear estimate is easier to use in downstream blocks to make adjustments.
author: Tom Rondeau <tom@trondeau.com> 2016-06-14 10:33:51 -0700
committer: Martin Braun <martin.braun@ettus.com> 2016-06-14 10:58:05 -0700
commit: 32d1c7d3188bf3107b45f350e44907cf23faee3e (patch)
tree: de3870cf17fef15d37199534507de9701ae05e78
parent: e2004886d012076e3835b148462d1c52480a6e88 (diff)
4 files changed, 2591 insertions, 31 deletions
diff --git a/gr-digital/examples/packet/example_corr_est.grc b/gr-digital/examples/packet/example_corr_est.grc
new file mode 100644
index 0000000000..ca07ce1cad
--- /dev/null
+++ b/gr-digital/examples/packet/example_corr_est.grc
@@ -0,0 +1,2530 @@
+<?xml version='1.0' encoding='utf-8'?>
+<?grc format='1' created='3.7.10'?>
+<flow_graph>
+  <timestamp>Tue Apr  5 13:57:36 2016</timestamp>
+  <block>
+    <key>options</key>
+    <param>
+      <key>author</key>
+      <value></value>
+    </param>
+    <param>
+      <key>window_size</key>
+      <value></value>
+    </param>
+    <param>
+      <key>category</key>
+      <value>Custom</value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>description</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(8, 11)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>generate_options</key>
+      <value>qt_gui</value>
+    </param>
+    <param>
+      <key>hier_block_src_path</key>
+      <value>.:</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>example_corr_est</value>
+    </param>
+    <param>
+      <key>max_nouts</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>qt_qss_theme</key>
+      <value></value>
+    </param>
+    <param>
+      <key>realtime_scheduling</key>
+      <value></value>
+    </param>
+    <param>
+      <key>run_command</key>
+      <value>{python} -u {filename}</value>
+    </param>
+    <param>
+      <key>run_options</key>
+      <value>prompt</value>
+    </param>
+    <param>
+      <key>run</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>thread_safe_setters</key>
+      <value></value>
+    </param>
+    <param>
+      <key>title</key>
+      <value></value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(264, 11)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>ac</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>map(lambda x: int(x), list(digital.packet_utils.default_access_code))</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(504, 579)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>ac_hex</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>[0xac, 0xdd, 0xa4, 0xe2, 0xf2, 0x8c, 0x20, 0xfc]</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(584, 515)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>eb</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>0.22</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(768, 515)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>filt_delay</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>1+(len(rrc_taps)-1)/2</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_qtgui_range</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(48, 563)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>1,0,1,1</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>freq_off</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value>Freq. Off.</value>
+    </param>
+    <param>
+      <key>min_len</key>
+      <value>200</value>
+    </param>
+    <param>
+      <key>orient</key>
+      <value>Qt.Horizontal</value>
+    </param>
+    <param>
+      <key>start</key>
+      <value>-0.25</value>
+    </param>
+    <param>
+      <key>step</key>
+      <value>0.0001</value>
+    </param>
+    <param>
+      <key>stop</key>
+      <value>0.25</value>
+    </param>
+    <param>
+      <key>rangeType</key>
+      <value>float</value>
+    </param>
+    <param>
+      <key>widget</key>
+      <value>counter_slider</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_constellation</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>const_points</key>
+      <value>digital.psk_2()[0]</value>
+    </param>
+    <param>
+      <key>dims</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(936, 243)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>hdr_const</value>
+    </param>
+    <param>
+      <key>rot_sym</key>
+      <value>2</value>
+    </param>
+    <param>
+      <key>soft_dec_lut</key>
+      <value>'auto'</value>
+    </param>
+    <param>
+      <key>precision</key>
+      <value>8</value>
+    </param>
+    <param>
+      <key>sym_map</key>
+      <value>digital.psk_2()[1]</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(672, 515)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>mark_delay</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>38</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_modulate_vector</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>data</key>
+      <value>ac_hex</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>taps</key>
+      <value>[1]</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(936, 371)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>modulated_sync_word</value>
+    </param>
+    <param>
+      <key>mod</key>
+      <value>rxmod</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_qtgui_range</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>-50</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(176, 435)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>0,1,1,1</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>noise</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value>Noise Power</value>
+    </param>
+    <param>
+      <key>min_len</key>
+      <value>200</value>
+    </param>
+    <param>
+      <key>orient</key>
+      <value>Qt.Horizontal</value>
+    </param>
+    <param>
+      <key>start</key>
+      <value>-50</value>
+    </param>
+    <param>
+      <key>step</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>stop</key>
+      <value>10</value>
+    </param>
+    <param>
+      <key>rangeType</key>
+      <value>float</value>
+    </param>
+    <param>
+      <key>widget</key>
+      <value>counter_slider</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_qtgui_range</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>10</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(48, 435)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>0,0,1,1</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>path_loss</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value>Path Loss (dB)</value>
+    </param>
+    <param>
+      <key>min_len</key>
+      <value>200</value>
+    </param>
+    <param>
+      <key>orient</key>
+      <value>Qt.Horizontal</value>
+    </param>
+    <param>
+      <key>start</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>step</key>
+      <value>5</value>
+    </param>
+    <param>
+      <key>stop</key>
+      <value>140</value>
+    </param>
+    <param>
+      <key>rangeType</key>
+      <value>float</value>
+    </param>
+    <param>
+      <key>widget</key>
+      <value>counter_slider</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_rrc_filter_taps</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>alpha</key>
+      <value>eb</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(1096, 243)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>gain</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>rrc_taps</value>
+    </param>
+    <param>
+      <key>ntaps</key>
+      <value>11*sps</value>
+    </param>
+    <param>
+      <key>samp_rate</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>sym_rate</key>
+      <value>1.0</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_rrc_filter_taps</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha</key>
+      <value>eb</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(304, 515)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>gain</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>rx_psf_taps</value>
+    </param>
+    <param>
+      <key>ntaps</key>
+      <value>15*sps</value>
+    </param>
+    <param>
+      <key>samp_rate</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>sym_rate</key>
+      <value>1.0</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(672, 579)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>rxmod</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>digital.generic_mod(hdr_const, False, sps, True, eb, False, False)</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
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+      <value>(168, 11)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>samp_rate</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>10e3</value>
+    </param>
+  </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(512, 515)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>4</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_qtgui_range</key>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(176, 563)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>1,1,1,1</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>time_off</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value>Time Off.</value>
+    </param>
+    <param>
+      <key>min_len</key>
+      <value>200</value>
+    </param>
+    <param>
+      <key>orient</key>
+      <value>Qt.Horizontal</value>
+    </param>
+    <param>
+      <key>start</key>
+      <value>0.9999</value>
+    </param>
+    <param>
+      <key>step</key>
+      <value>0.00001</value>
+    </param>
+    <param>
+      <key>stop</key>
+      <value>1.0001</value>
+    </param>
+    <param>
+      <key>rangeType</key>
+      <value>float</value>
+    </param>
+    <param>
+      <key>widget</key>
+      <value>counter_slider</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_add_const_vxx</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>const</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(368, 107)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_add_const_vxx_0</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_complex_to_mag_squared</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(528, 393)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_complex_to_mag_squared_0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_multiply_const_vxx</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>const</key>
+      <value>2</value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(216, 107)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_multiply_const_vxx_0</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_stream_to_tagged_stream</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(664, 99)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_stream_to_tagged_stream_0</value>
+    </param>
+    <param>
+      <key>len_tag_key</key>
+      <value>"packet_len"</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>packet_len</key>
+      <value>len(ac)+16</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_throttle</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(504, 107)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_throttle_0</value>
+    </param>
+    <param>
+      <key>ignoretag</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>samples_per_second</key>
+      <value>samp_rate</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_vector_source_x</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(16, 91)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>blocks_vector_source_x_0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>repeat</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>tags</key>
+      <value>[]</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>vector</key>
+      <value>[1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0] + ac</value>
+    </param>
+  </block>
+  <block>
+    <key>channels_channel_model</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>block_tags</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>epsilon</key>
+      <value>time_off</value>
+    </param>
+    <param>
+      <key>freq_offset</key>
+      <value>freq_off</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(48, 203)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>channels_channel_model_0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>noise_voltage</key>
+      <value>sps * 10.0**(noise/10.0)</value>
+    </param>
+    <param>
+      <key>seed</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>taps</key>
+      <value>10.0**(-path_loss/20.0)</value>
+    </param>
+  </block>
+  <block>
+    <key>digital_corr_est_cc</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(264, 211)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>digital_corr_est_cc_0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>sps</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>scale_factor</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>symbols</key>
+      <value>modulated_sync_word</value>
+    </param>
+    <param>
+      <key>mark_delay</key>
+      <value>mark_delay</value>
+    </param>
+    <param>
+      <key>threshold</key>
+      <value>0.999</value>
+    </param>
+  </block>
+  <block>
+    <key>fir_filter_xxx</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>decim</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(528, 219)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>fir_filter_xxx_0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>samp_delay</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>taps</key>
+      <value>rx_psf_taps</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>ccc</value>
+    </param>
+  </block>
+  <block>
+    <key>interp_fir_filter_xxx</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(896, 99)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>interp_fir_filter_xxx_0</value>
+    </param>
+    <param>
+      <key>interp</key>
+      <value>sps</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>samp_delay</key>
+      <value>filt_delay</value>
+    </param>
+    <param>
+      <key>taps</key>
+      <value>rrc_taps</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>ccc</value>
+    </param>
+  </block>
+  <block>
+    <key>qtgui_time_sink_x</key>
+    <param>
+      <key>autoscale</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>ctrlpanel</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>entags</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(720, 211)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>2,0,1,2</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>grid</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>qtgui_time_sink_x_0</value>
+    </param>
+    <param>
+      <key>legend</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alpha1</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color1</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label1</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker1</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha10</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color10</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label10</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker10</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha2</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color2</key>
+      <value>"red"</value>
+    </param>
+    <param>
+      <key>label2</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker2</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha3</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color3</key>
+      <value>"green"</value>
+    </param>
+    <param>
+      <key>label3</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker3</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha4</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color4</key>
+      <value>"black"</value>
+    </param>
+    <param>
+      <key>label4</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker4</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha5</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color5</key>
+      <value>"cyan"</value>
+    </param>
+    <param>
+      <key>label5</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker5</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha6</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color6</key>
+      <value>"magenta"</value>
+    </param>
+    <param>
+      <key>label6</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker6</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha7</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color7</key>
+      <value>"yellow"</value>
+    </param>
+    <param>
+      <key>label7</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker7</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha8</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color8</key>
+      <value>"dark red"</value>
+    </param>
+    <param>
+      <key>label8</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker8</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha9</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color9</key>
+      <value>"dark green"</value>
+    </param>
+    <param>
+      <key>label9</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker9</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>name</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>nconnections</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>size</key>
+      <value>512</value>
+    </param>
+    <param>
+      <key>srate</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>tr_chan</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>tr_delay</key>
+      <value>15</value>
+    </param>
+    <param>
+      <key>tr_level</key>
+      <value>0.0</value>
+    </param>
+    <param>
+      <key>tr_mode</key>
+      <value>qtgui.TRIG_MODE_TAG</value>
+    </param>
+    <param>
+      <key>tr_slope</key>
+      <value>qtgui.TRIG_SLOPE_POS</value>
+    </param>
+    <param>
+      <key>tr_tag</key>
+      <value>corr_start</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>update_time</key>
+      <value>0.10</value>
+    </param>
+    <param>
+      <key>ylabel</key>
+      <value>Amplitude</value>
+    </param>
+    <param>
+      <key>yunit</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>ymax</key>
+      <value>1.5</value>
+    </param>
+    <param>
+      <key>ymin</key>
+      <value>-1.5</value>
+    </param>
+  </block>
+  <block>
+    <key>qtgui_time_sink_x</key>
+    <param>
+      <key>autoscale</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>ctrlpanel</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>entags</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(528, 299)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>tab0@0</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>grid</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>qtgui_time_sink_x_0_0</value>
+    </param>
+    <param>
+      <key>legend</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alpha1</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color1</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label1</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker1</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha10</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color10</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label10</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker10</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha2</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color2</key>
+      <value>"red"</value>
+    </param>
+    <param>
+      <key>label2</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker2</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha3</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color3</key>
+      <value>"green"</value>
+    </param>
+    <param>
+      <key>label3</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker3</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha4</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color4</key>
+      <value>"black"</value>
+    </param>
+    <param>
+      <key>label4</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker4</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha5</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color5</key>
+      <value>"cyan"</value>
+    </param>
+    <param>
+      <key>label5</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker5</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha6</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color6</key>
+      <value>"magenta"</value>
+    </param>
+    <param>
+      <key>label6</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker6</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha7</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color7</key>
+      <value>"yellow"</value>
+    </param>
+    <param>
+      <key>label7</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker7</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha8</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color8</key>
+      <value>"dark red"</value>
+    </param>
+    <param>
+      <key>label8</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker8</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha9</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color9</key>
+      <value>"dark green"</value>
+    </param>
+    <param>
+      <key>label9</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker9</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>name</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>nconnections</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>size</key>
+      <value>512</value>
+    </param>
+    <param>
+      <key>srate</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>tr_chan</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>tr_delay</key>
+      <value>15</value>
+    </param>
+    <param>
+      <key>tr_level</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>tr_mode</key>
+      <value>qtgui.TRIG_MODE_TAG</value>
+    </param>
+    <param>
+      <key>tr_slope</key>
+      <value>qtgui.TRIG_SLOPE_POS</value>
+    </param>
+    <param>
+      <key>tr_tag</key>
+      <value>corr_est</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>complex</value>
+    </param>
+    <param>
+      <key>update_time</key>
+      <value>0.10</value>
+    </param>
+    <param>
+      <key>ylabel</key>
+      <value>Amplitude</value>
+    </param>
+    <param>
+      <key>yunit</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>ymax</key>
+      <value>100</value>
+    </param>
+    <param>
+      <key>ymin</key>
+      <value>-100</value>
+    </param>
+  </block>
+  <block>
+    <key>qtgui_time_sink_x</key>
+    <param>
+      <key>autoscale</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>ctrlpanel</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>entags</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(720, 371)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value>tab0@1</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>grid</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>qtgui_time_sink_x_0_0_0</value>
+    </param>
+    <param>
+      <key>legend</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alpha1</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color1</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label1</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker1</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width1</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha10</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color10</key>
+      <value>"blue"</value>
+    </param>
+    <param>
+      <key>label10</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker10</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width10</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha2</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color2</key>
+      <value>"red"</value>
+    </param>
+    <param>
+      <key>label2</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker2</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width2</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha3</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color3</key>
+      <value>"green"</value>
+    </param>
+    <param>
+      <key>label3</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker3</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width3</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha4</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color4</key>
+      <value>"black"</value>
+    </param>
+    <param>
+      <key>label4</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker4</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width4</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha5</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color5</key>
+      <value>"cyan"</value>
+    </param>
+    <param>
+      <key>label5</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker5</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width5</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha6</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color6</key>
+      <value>"magenta"</value>
+    </param>
+    <param>
+      <key>label6</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker6</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width6</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha7</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color7</key>
+      <value>"yellow"</value>
+    </param>
+    <param>
+      <key>label7</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker7</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width7</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha8</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color8</key>
+      <value>"dark red"</value>
+    </param>
+    <param>
+      <key>label8</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker8</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width8</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>alpha9</key>
+      <value>1.0</value>
+    </param>
+    <param>
+      <key>color9</key>
+      <value>"dark green"</value>
+    </param>
+    <param>
+      <key>label9</key>
+      <value></value>
+    </param>
+    <param>
+      <key>marker9</key>
+      <value>-1</value>
+    </param>
+    <param>
+      <key>style9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>width9</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>name</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>nconnections</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>size</key>
+      <value>512</value>
+    </param>
+    <param>
+      <key>srate</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>tr_chan</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>tr_delay</key>
+      <value>15</value>
+    </param>
+    <param>
+      <key>tr_level</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>tr_mode</key>
+      <value>qtgui.TRIG_MODE_TAG</value>
+    </param>
+    <param>
+      <key>tr_slope</key>
+      <value>qtgui.TRIG_SLOPE_POS</value>
+    </param>
+    <param>
+      <key>tr_tag</key>
+      <value>corr_est</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>float</value>
+    </param>
+    <param>
+      <key>update_time</key>
+      <value>0.10</value>
+    </param>
+    <param>
+      <key>ylabel</key>
+      <value>Amplitude</value>
+    </param>
+    <param>
+      <key>yunit</key>
+      <value>""</value>
+    </param>
+    <param>
+      <key>ymax</key>
+      <value>4000</value>
+    </param>
+    <param>
+      <key>ymin</key>
+      <value>-100</value>
+    </param>
+  </block>
+  <block>
+    <key>qtgui_tab_widget</key>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>comment</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(296, 435)</value>
+    </param>
+    <param>
+      <key>gui_hint</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>id</key>
+      <value>tab0</value>
+    </param>
+    <param>
+      <key>label0</key>
+      <value>Corr</value>
+    </param>
+    <param>
+      <key>label1</key>
+      <value>|Corr|^2</value>
+    </param>
+    <param>
+      <key>label10</key>
+      <value>Tab 10</value>
+    </param>
+    <param>
+      <key>label11</key>
+      <value>Tab 11</value>
+    </param>
+    <param>
+      <key>label12</key>
+      <value>Tab 12</value>
+    </param>
+    <param>
+      <key>label13</key>
+      <value>Tab 13</value>
+    </param>
+    <param>
+      <key>label14</key>
+      <value>Tab 14</value>
+    </param>
+    <param>
+      <key>label15</key>
+      <value>Tab 15</value>
+    </param>
+    <param>
+      <key>label16</key>
+      <value>Tab 16</value>
+    </param>
+    <param>
+      <key>label17</key>
+      <value>Tab 17</value>
+    </param>
+    <param>
+      <key>label18</key>
+      <value>Tab 18</value>
+    </param>
+    <param>
+      <key>label19</key>
+      <value>Tab 19</value>
+    </param>
+    <param>
+      <key>label2</key>
+      <value>Tab 2</value>
+    </param>
+    <param>
+      <key>label3</key>
+      <value>Tab 3</value>
+    </param>
+    <param>
+      <key>label4</key>
+      <value>Tab 4</value>
+    </param>
+    <param>
+      <key>label5</key>
+      <value>Tab 5</value>
+    </param>
+    <param>
+      <key>label6</key>
+      <value>Tab 6</value>
+    </param>
+    <param>
+      <key>label7</key>
+      <value>Tab 7</value>
+    </param>
+    <param>
+      <key>label8</key>
+      <value>Tab 8</value>
+    </param>
+    <param>
+      <key>label9</key>
+      <value>Tab 9</value>
+    </param>
+    <param>
+      <key>num_tabs</key>
+      <value>2</value>
+    </param>
+  </block>
+  <connection>
+    <source_block_id>blocks_add_const_vxx_0</source_block_id>
+    <sink_block_id>blocks_throttle_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>blocks_complex_to_mag_squared_0</source_block_id>
+    <sink_block_id>qtgui_time_sink_x_0_0_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>blocks_multiply_const_vxx_0</source_block_id>
+    <sink_block_id>blocks_add_const_vxx_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>blocks_stream_to_tagged_stream_0</source_block_id>
+    <sink_block_id>interp_fir_filter_xxx_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>blocks_throttle_0</source_block_id>
+    <sink_block_id>blocks_stream_to_tagged_stream_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>blocks_vector_source_x_0</source_block_id>
+    <sink_block_id>blocks_multiply_const_vxx_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>channels_channel_model_0</source_block_id>
+    <sink_block_id>digital_corr_est_cc_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>digital_corr_est_cc_0</source_block_id>
+    <sink_block_id>blocks_complex_to_mag_squared_0</sink_block_id>
+    <source_key>1</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>digital_corr_est_cc_0</source_block_id>
+    <sink_block_id>qtgui_time_sink_x_0_0</sink_block_id>
+    <source_key>1</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>digital_corr_est_cc_0</source_block_id>
+    <sink_block_id>fir_filter_xxx_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>fir_filter_xxx_0</source_block_id>
+    <sink_block_id>qtgui_time_sink_x_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>interp_fir_filter_xxx_0</source_block_id>
+    <sink_block_id>channels_channel_model_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
+</flow_graph>
diff --git a/gr-digital/include/gnuradio/digital/corr_est_cc.h b/gr-digital/include/gnuradio/digital/corr_est_cc.h
index e8211cf60b..237a499b6b 100644
--- a/gr-digital/include/gnuradio/digital/corr_est_cc.h
+++ b/gr-digital/include/gnuradio/digital/corr_est_cc.h
@@ -42,6 +42,7 @@ namespace gr {
      * \li tag 'phase_est': estimate of phase offset
      * \li tag 'time_est': estimate of symbol timing offset
      * \li tag 'corr_est': the correlation value of the estimates
+     * \li tag 'amp_est': 1 over the estimated amplitude
      * \li tag 'corr_start': the start sample of the correlation and the value
      *
      * \li Optional 2nd output stream providing the advanced correlator output
@@ -51,12 +52,11 @@ namespace gr {
      * offset estimate. These estimates are passed downstream as
      * stream tags for use by follow-on synchronization blocks.
      *
-     * The sync word is provided as a set of symbols along with a
-     * baseband matched filter which we use to create the filtered and
-     * upsampled symbols that we will receive over-the-air.
+     * The sync word is provided as a set of symbols after being
+     * filtered by a baseband matched filter.
      *
      * The phase_est tag can be used by downstream blocks to adjust
-     * their phase estimatopm/correction loops, and is currently
+     * their phase estimator/correction loops, and is currently
      * implemented by the gr::digital::costas_loop_cc block.
      *
      * The time_est tag can be used to adjust the sampling timing
diff --git a/gr-digital/lib/corr_est_cc_impl.cc b/gr-digital/lib/corr_est_cc_impl.cc
index 772fc780dc..dfcd966b05 100644
--- a/gr-digital/lib/corr_est_cc_impl.cc
+++ b/gr-digital/lib/corr_est_cc_impl.cc
@@ -55,6 +55,17 @@ namespace gr {
     {
       d_sps = sps;
 
+      // In order to easily support the optional second output,
+      // don't deal with an unbounded max number of output items.
+      // For the common case of not using the optional second output,
+      // this ensures we optimally call the volk routines.
+      const size_t nitems = 24*1024;
+      set_max_noutput_items(nitems);
+      d_corr = (gr_complex *)
+               volk_malloc(sizeof(gr_complex)*nitems, volk_get_alignment());
+      d_corr_mag = (float *)
+                   volk_malloc(sizeof(float)*nitems, volk_get_alignment());
+
       // Create time-reversed conjugate of symbols
       d_symbols = symbols;
       for(size_t i=0; i < d_symbols.size(); i++) {
@@ -96,16 +107,7 @@ namespace gr {
       //  volk_get_alignment() / sizeof(gr_complex);
       //set_alignment(std::max(1,alignment_multiple));
 
-      // In order to easily support the optional second output,
-      // don't deal with an unbounded max number of output items.
-      // For the common case of not using the optional second output,
-      // this ensures we optimally call the volk routines.
-      const size_t nitems = 24*1024;
-      set_max_noutput_items(nitems);
-      d_corr = (gr_complex *)
-               volk_malloc(sizeof(gr_complex)*nitems, volk_get_alignment());
-      d_corr_mag = (float *)
-                   volk_malloc(sizeof(float)*nitems, volk_get_alignment());
+      d_scale = 1.0f;
     }
 
     corr_est_cc_impl::~corr_est_cc_impl()
@@ -193,14 +195,7 @@ namespace gr {
     corr_est_cc_impl::_set_threshold(float threshold)
     {
       d_stashed_threshold = threshold;
-
-      // Compute a correlation threshold.
-      // Compute the value of the discrete autocorrelation of the matched
-      // filter with offset 0 (aka the autocorrelation peak).
-      float corr = 0;
-      for(size_t i = 0; i < d_symbols.size(); i++)
-        corr += abs(d_symbols[i]*conj(d_symbols[i]));
-      d_thresh = threshold*corr*corr;
+      d_pfa = -logf(1.0f-threshold);
     }
 
     void
@@ -228,10 +223,6 @@ namespace gr {
       // Our correlation filter length
       unsigned int hist_len = history() - 1;
 
-      // Delay the output by our correlation filter length so we can
-      // tag backwards in time
-      memcpy(out, &in[0], sizeof(gr_complex)*noutput_items);
-
       // Calculate the correlation of the non-delayed input with the
       // known symbols.
       d_filter->filter(noutput_items, &in[hist_len], corr);
@@ -239,19 +230,31 @@ namespace gr {
       // Find the magnitude squared of the correlation
       volk_32fc_magnitude_squared_32f(&d_corr_mag[0], corr, noutput_items);
 
+      float detection = 0;
+      for(int i = 0; i < noutput_items; i++) {
+        detection += d_corr_mag[i];
+      }
+      detection /= static_cast<float>(noutput_items);
+      detection *= d_pfa;
+
       int isps = (int)(d_sps + 0.5f);
       int i = 0;
       while(i < noutput_items) {
-        // Look for the correlator output to cross the threshold
-        if (d_corr_mag[i] <= d_thresh) {
+        // Look for the correlator output to cross the threshold.
+        // Sum power over two consecutive symbols in case we're offset
+        // in time. If off by 1/2 a symbol, the peak of any one point
+        // is much lower.
+        float corr_mag = d_corr_mag[i] + d_corr_mag[i+1];
+        if(corr_mag <= 4*detection) {
           i++;
           continue;
         }
+
         // Go to (just past) the current correlator output peak
         while ((i < (noutput_items-1)) &&
-               (d_corr_mag[i] < d_corr_mag[i+1]))
+               (d_corr_mag[i] < d_corr_mag[i+1])) {
           i++;
-
+        }
         // Delaying the primary signal output by the matched filter
         // length using history(), means that the the peak output of
         // the matched filter aligns with the start of the desired
@@ -262,8 +265,9 @@ namespace gr {
         add_item_tag(0, nitems_written(0) + i, pmt::intern("corr_start"),
                      pmt::from_double(d_corr_mag[i]), d_src_id);
 
+#if 0
         // Use Parabolic interpolation to estimate a fractional
-        // sample delay. There are more accurate methods as 
+        // sample delay. There are more accurate methods as
         // the sample delay estimate using this method is biased.
         // But this method is simple and fast.
         // center between [-0.5,0.5] units of samples
@@ -275,6 +279,21 @@ namespace gr {
           double denom = 2*(d_corr_mag[i-1]-2*d_corr_mag[i]+d_corr_mag[i+1]);
           center = nom/denom;
         }
+#else
+        // Calculates the center of mass between the three points around the peak.
+        // Estimate is linear.
+        double nom = 0, den = 0;
+        nom = d_corr_mag[i-1] + 2*d_corr_mag[i] + 3*d_corr_mag[i+1];
+        den = d_corr_mag[i-1] + d_corr_mag[i] + d_corr_mag[i+1];
+        double center = nom / den;
+        center = (center - 2.0); // adjust for bias in center of mass calculation
+#endif
+
+        // Estimated scaling factor for the input stream to normalize
+        // the output to +/-1.
+        uint32_t maxi;
+        volk_32fc_index_max_16u(&maxi, (gr_complex*)in, noutput_items);
+        d_scale = 1 / std::abs(in[maxi]);
 
         // Calculate the phase offset of the incoming signal.
         //
@@ -304,6 +323,8 @@ namespace gr {
         // N.B. the appropriate d_corr_mag[] index is "i", not "index".
         add_item_tag(0, nitems_written(0) + index, pmt::intern("corr_est"),
                      pmt::from_double(d_corr_mag[i]), d_src_id);
+        add_item_tag(0, nitems_written(0) + index, pmt::intern("amp_est"),
+                     pmt::from_double(d_scale), d_src_id);
 
         if (output_items.size() > 1) {
           // N.B. these debug tags are not offset to avoid walking off out buf
@@ -313,6 +334,8 @@ namespace gr {
                        pmt::from_double(center), d_src_id);
           add_item_tag(1, nitems_written(0) + i, pmt::intern("corr_est"),
                        pmt::from_double(d_corr_mag[i]), d_src_id);
+          add_item_tag(1, nitems_written(0) + i, pmt::intern("amp_est"),
+                       pmt::from_double(d_scale), d_src_id);
         }
 
         // Skip ahead to the next potential symbol peak
@@ -325,6 +348,10 @@ namespace gr {
       //               pmt::intern("ce_eow"), pmt::from_uint64(noutput_items),
       //               d_src_id);
 
+      // Delay the output by our correlation filter length so we can
+      // tag backwards in time
+      memcpy(out, &in[0], sizeof(gr_complex)*noutput_items);
+
       return noutput_items;
     }
 
diff --git a/gr-digital/lib/corr_est_cc_impl.h b/gr-digital/lib/corr_est_cc_impl.h
index 6e8dd17083..e0d4c8ef25 100644
--- a/gr-digital/lib/corr_est_cc_impl.h
+++ b/gr-digital/lib/corr_est_cc_impl.h
@@ -44,6 +44,9 @@ namespace gr {
       gr_complex *d_corr;
       float *d_corr_mag;
 
+      float d_scale;
+      float d_pfa; // probability of false alarm
+
       void _set_mark_delay(unsigned int mark_delay);
       void _set_threshold(float threshold);
author	Tom Rondeau <tom@trondeau.com>	2016-06-14 10:33:51 -0700
committer	Martin Braun <martin.braun@ettus.com>	2016-06-14 10:58:05 -0700
commit	32d1c7d3188bf3107b45f350e44907cf23faee3e (patch)
tree	de3870cf17fef15d37199534507de9701ae05e78
parent	e2004886d012076e3835b148462d1c52480a6e88 (diff)