[Commit-gnuradio] r8143 - gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general

[trondeau]

Author: trondeau
Date: 2008-03-31 16:42:14 -0600 (Mon, 31 Mar 2008)
New Revision: 8143

Modified:
   
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_frame_sink.cc
   
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_mapper_bcv.cc
Log:
appropriately places subcarriers around the nulled DC carriers. Works for all 
multiples of 4 occupied-tones, which is a restriction we placed in it from 
another time.

Modified: 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_frame_sink.cc
===================================================================
--- 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_frame_sink.cc
      2008-03-31 18:22:13 UTC (rev 8142)
+++ 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_frame_sink.cc
      2008-03-31 22:42:14 UTC (rev 8143)
@@ -212,25 +212,39 @@
   }
   
   // if there's extras left to be processed
-  // put the first carriers onto the end if there's at least 4 carriers
-  if(diff >= 4) {
-    carriers.insert(carriers.length(), "f");
-    diff -= 4;
-  }
-  // if we still have carriers left, stick them in front
-  if(diff) {
+  // divide remaining to put on either side of current map
+  // all of this is done to stick with the concept of a carrier map string that
+  // can be later passed by the user, even though it'd be cleaner to just do 
this
+  // on the carrier map itself
+  int diff_left=0;
+  int diff_right=0;
+
+  // dictionary to convert from integers to ascii hex representation
+  char abc[16] = {'0', '1', '2', '3', '4', '5', '6', '7', 
+                 '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+  if(diff > 0) {
     char c[2] = {0,0};
-    c[0] = (pow(2,diff) - 1) + 0x30;
+
+    diff_left = (int)ceil((float)diff/2.0f);  // number of carriers to put on 
the left side
+    c[0] = abc[((1 << diff_left) - 1)];       // convert to bits and move to 
ASCI integer
     carriers.insert(0, c);
+    
+    diff_right = diff - diff_left;           // number of carriers to put on 
the right side
+    c[0] = abc[(0xF^(1 << diff_left) - 1)];   // convert to bits and move to 
ASCI integer
+    carriers.insert(carriers.length(), c);
   }
 
-  int i,j,k;
-  for(i = 0; i < (int)(d_occupied_carriers/4); i++) {
+  // It seemed like such a good idea at the time...
+  // because we are only dealing with the occupied_carriers
+  // at this point, the diff_left in the following compensates
+  // for any offset from the 0th carrier introduced
+  unsigned int i,j,k;
+  for(i = 0; i < (d_occupied_carriers/4)+diff_left; i++) {
     char c = carriers[i];
     for(j = 0; j < 4; j++) {
       k = (strtol(&c, NULL, 16) >> (3-j)) & 0x1;
       if(k) {
-       d_subcarrier_map.push_back(4*i + j);
+       d_subcarrier_map.push_back(4*i + j - diff_left);
       }
     }
   }

Modified: 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_mapper_bcv.cc
===================================================================
--- 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_mapper_bcv.cc
      2008-03-31 18:22:13 UTC (rev 8142)
+++ 
gnuradio/branches/developers/trondeau/ofdm/gnuradio-core/src/lib/general/gr_ofdm_mapper_bcv.cc
      2008-03-31 22:42:14 UTC (rev 8143)
@@ -67,17 +67,28 @@
     carriers.insert(carriers.length(), "f");
     diff -= 8;
   }
+
   // if there's extras left to be processed
-  // put the first carriers onto the end if there's at least 4 carriers
-  if(diff >= 4) {
-    carriers.insert(carriers.length(), "f");
-    diff -= 4;
-  }
-  // if we still have carriers left, stick them in front
-  if(diff) {
+  // divide remaining to put on either side of current map
+  // all of this is done to stick with the concept of a carrier map string that
+  // can be later passed by the user, even though it'd be cleaner to just do 
this
+  // on the carrier map itself
+  int diff_left=0;
+  int diff_right=0;
+
+  // dictionary to convert from integers to ascii hex representation
+  char abc[16] = {'0', '1', '2', '3', '4', '5', '6', '7', 
+                 '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+  if(diff > 0) {
     char c[2] = {0,0};
-    c[0] = (pow(2,diff) - 1) + 0x30;
+
+    diff_left = (int)ceil((float)diff/2.0f);   // number of carriers to put on 
the left side
+    c[0] = abc[((1 << diff_left) - 1)];        // convert to bits and move to 
ASCI integer
     carriers.insert(0, c);
+    
+    diff_right = diff - diff_left;            // number of carriers to put on 
the right side
+    c[0] = abc[(0xF^(1 << diff_left) - 1)];    // convert to bits and move to 
ASCI integer
+        carriers.insert(carriers.length(), c);
   }
   
   // find out how many zeros to pad on the sides; the difference between the 
fft length and the subcarrier
@@ -88,8 +99,8 @@
   unsigned int i,j,k;
   for(i = 0; i < carriers.length(); i++) {
     char c = carriers[i];                            // get the current hex 
character from the string
-    for(j = 0; j < 4; j++) {                        // walk through all four 
bits
-      k = (strtol(&c, NULL, 16) >> (3-j)) & 0x1;          // convert to int 
and extract next bit
+    for(j = 0; j < 4; j++) {                         // walk through all four 
bits
+      k = (strtol(&c, NULL, 16) >> (3-j)) & 0x1;     // convert to int and 
extract next bit
       if(k) {                                        // if bit is a 1, 
        d_subcarrier_map.push_back(4*(i+diff) + j);  // use this subcarrier
       }