[Commit-gnuradio] [gnuradio] 06/10: gr-fec: update/add documentation for LDPC GRC blocks.

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commit f91929b8fc88019e6143145fd5b0ead995d9215a
Author: tracierenea <address@hidden>
Date:   Sun Mar 20 21:24:41 2016 -0500

    gr-fec: update/add documentation for LDPC GRC blocks.
---
 gr-fec/grc/ldpc_decoder_def_list.xml          | 6 +++++-
 gr-fec/grc/variable_ldpc_G_matrix_object.xml  | 2 +-
 gr-fec/grc/variable_ldpc_H_matrix_object.xml  | 2 +-
 gr-fec/grc/variable_ldpc_bit_flip_decoder.xml | 6 ++----
 gr-fec/grc/variable_ldpc_encoder_G.xml        | 7 ++++++-
 gr-fec/grc/variable_ldpc_encoder_H.xml        | 6 +++++-
 6 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/gr-fec/grc/ldpc_decoder_def_list.xml 
b/gr-fec/grc/ldpc_decoder_def_list.xml
index 8304e03..007f855 100644
--- a/gr-fec/grc/ldpc_decoder_def_list.xml
+++ b/gr-fec/grc/ldpc_decoder_def_list.xml
@@ -78,6 +78,10 @@ self.$(id) = $(id) = map( (lambda b: map( ( lambda a: 
fec.ldpc_decoder.make($fil
     </param>
 
     <doc>
-        This block does some kind of ldpc
+This is a soft-decision decoder that uses belief propagation (also known as 
message passing) that is described at:
+
+www.cs.toronto.edu/~radford/ftp/LDPC-2012-02-11/decoding.html
+
+Designed for a memoryless AWGN channel, it assumes a noise variance of the 
value specified for sigma.
     </doc>
 </block>
diff --git a/gr-fec/grc/variable_ldpc_G_matrix_object.xml 
b/gr-fec/grc/variable_ldpc_G_matrix_object.xml
index cd6b02c..cd9360c 100644
--- a/gr-fec/grc/variable_ldpc_G_matrix_object.xml
+++ b/gr-fec/grc/variable_ldpc_G_matrix_object.xml
@@ -32,7 +32,7 @@
 This block creates a LDPC Generator Matrix variable.
 
 This variable can be used by:
-  1) LDPC Generator Matrix Encoder Definition block
+  1) LDPC Encoder Definition (via Generator) block
   2) LDPC Bit Flip Decoder Definition block
 
 Provide an alist file, which contains a Generator matrix, G, in the standard 
format G = [I P], where I is an identity matrix and P is the parity submatrix.
diff --git a/gr-fec/grc/variable_ldpc_H_matrix_object.xml 
b/gr-fec/grc/variable_ldpc_H_matrix_object.xml
index 81476d6..1bfb6be 100644
--- a/gr-fec/grc/variable_ldpc_H_matrix_object.xml
+++ b/gr-fec/grc/variable_ldpc_H_matrix_object.xml
@@ -38,7 +38,7 @@
 This block creates a FEC LDPC Parity Check Matrix variable.
 
 This variable can be used by:
-  1) LDPC Encoder Definition block
+  1) LDPC Encoder Definition (via Parity Check) block
   2) LDPC Bit Flip Decoder Definition block
 
 The format of alist files is described at:
diff --git a/gr-fec/grc/variable_ldpc_bit_flip_decoder.xml 
b/gr-fec/grc/variable_ldpc_bit_flip_decoder.xml
index 2b407f3..dd9dabb 100644
--- a/gr-fec/grc/variable_ldpc_bit_flip_decoder.xml
+++ b/gr-fec/grc/variable_ldpc_bit_flip_decoder.xml
@@ -78,10 +78,8 @@ self.$(id) = $(id) = map((lambda b: map((lambda a: 
fec.ldpc_bit_flip_decoder.mak
 This block creates a LDPC Bit Flip Decoder Definition variable.
 
 The decoder requires knowledge of the matrix used to create (encode) the 
codewords. In the LDPC FEC Matrix ID field, input the ID of either a:
-  1) LDPC Matrix variable, or
-  2) LDPC R. U. Parity Check Matrix variable
-
-Be sure to specify the same matrix ID as the matrix that was used for encoding.
+  1) LDPC Generator Matrix variable, or
+  2) LDPC Parity Check Matrix variable
 
 Max iterations may be increased from 100 for possibly better performance, but 
significantly higher number of iterations may slow things down.
     </doc>
diff --git a/gr-fec/grc/variable_ldpc_encoder_G.xml 
b/gr-fec/grc/variable_ldpc_encoder_G.xml
index 74d95fa..d138fa3 100644
--- a/gr-fec/grc/variable_ldpc_encoder_G.xml
+++ b/gr-fec/grc/variable_ldpc_encoder_G.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!--
 ###################################################
-# FEC LDPC GENERATOR MATRIX ENCODER
+# FEC LDPC ENCODER DEFINITION (VIA GENERATOR)
 ###################################################
  -->
 
@@ -69,4 +69,9 @@ self.$(id) = $(id) = map((lambda b: map((lambda a: 
fec.ldpc_encoder_make($G)), r
     <type>raw</type>
   </param>
 
+  <doc>
+Given a generator matrix in systematic form, G = [I|P], where I is the 
identity matrix and P is the parity submatrix, the information word s is 
encoded into a codeword x via:
+
+x = G'*s
+  </doc>
 </block>
diff --git a/gr-fec/grc/variable_ldpc_encoder_H.xml 
b/gr-fec/grc/variable_ldpc_encoder_H.xml
index 403f809..555891b 100644
--- a/gr-fec/grc/variable_ldpc_encoder_H.xml
+++ b/gr-fec/grc/variable_ldpc_encoder_H.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!--
 ###################################################
-# FEC LDPC RICHARDSON URBANKE ENCODER
+# FEC LDPC ENCODER DEFINITION (PARITY CHECK)
 ###################################################
  -->
 <block>
@@ -67,5 +67,9 @@ self.$(id) = $(id) = map((lambda b: map((lambda a: 
fec.ldpc_par_mtrx_encoder_mak
         <value></value>
         <type>raw</type>
     </param>
+  <doc>
+This block creates a LDPC Encoder Definition variable.
 
+This encoder performs a reduced complexity algorithm described by Richardson 
and Urbanke in Appendix A of their book: Modern Coding Theory. Compared to the 
block "LDPC Encoder Definition (via Generator)," this encoder requires orders 
of magnitude fewer operations to create each codeword. This is accomplished by 
completing a significant amount of the complex matrix manipulation (including 
inverse, multiplication, and Gaussian elimination operations) during 
preprocessing. The disadvantage  [...]
+  </doc>
 </block>