updated gr-trellis documentation

1 files changed, 12 insertions, 2 deletions

diff --git a/gr-trellis/doc/gr-trellis.xml b/gr-trellis/doc/gr-trellis.xml
index 4f117ec38..5f1921343 100644
--- a/gr-trellis/doc/gr-trellis.xml
+++ b/gr-trellis/doc/gr-trellis.xml
@@ -822,7 +822,7 @@ The modulated symbols are filtered by the ISI channel and AWGN with appropriate
 
 <para>
 Since the output alphabet of the equivalent FSM is quite large (1024) we chose to utilize the combined metrics calculator and Viterbi algorithm block.
-also note that the first L observations are irrelevant and tus can be skipped.
+Also note that the first L observations are irrelevant and thus can be skipped.
 </para>
 <programlisting>
  33      # RX
@@ -873,7 +873,17 @@ The function returns the number of symbols and the number of symbols in error. O
 
 <para>
 Soft versions of the algorithms have been implemented.
-Also examples of turbo equalization/decoding and of sccc can be found in the examples directory.
+Also examples of turbo equalization/decoding and of sccc can
+be found in the examples directory.
+
+Recently we added gnuradio blocks for sccc and pccc encoders and 
+turbo decoders.
+Although these can be generated by existing gr-trellis blocks (in particular,
+the SISO blocks, as done in some of the python examples) there is an advantage
+in having this functionality as a single block. To see why, think of a turbo decoder with 10 iterations. Previously we needed to concatenate 10 x 2 SISO blocks
+(for a sccc decoder) to emulate the passing of soft information between SISOs over 10 iterartions. With the new block however, only a single such block is needed that internally loops through 10 iterations; this results in space savings
+and possibly time saving as well (since queueing at the input/ouput of the gr-blocks is avoided). 
+
 
 Still need to document them...
 </para>