channel::decode_mlse() : add a new unit test for MLSE time domain equ…

…alizer

inc/susa/channel.h

@@ -105,6 +105,7 @@ template <class T> class channel
      *
      * @param mat_arg the encoded signal vector
      * @param dbl_ebn0 the signal to noise ratio Eb/N0
+     * @return Log Likelihood Ratio (LLR) vector
      */
     matrix <T> decode_bcjr(const matrix <T> &mat_arg, T dbl_ebn0);
 
@@ -310,7 +311,6 @@ template <class T> matrix <T> channel <T>::decode_mlse(const matrix <T> &mat_arg
     }
 
 
-
     // Trace Back the Trellis (decoding)
     unsigned int uint_curr_state = uint_init_state;
     unsigned int uint_curr_input;
@@ -338,16 +338,13 @@ template <class T> matrix <T> channel <T>::decode_mlse(const matrix <T> &mat_arg
     // It detects the initial and final states.
 
     T dbl_metric = 0;
-    unsigned int uint_l = mat_taps.size() - 1;
-    unsigned int uint_num_stages = mat_arg.size() - 2 * uint_l;
-    unsigned int uint_num_states = uint_num_states_mem;
+    size_t sz_length = mat_arg.size();
+    size_t uint_l = mat_taps.size() - 1;
+    size_t uint_num_stages = sz_length - 2 * uint_l;
+    size_t uint_num_states = uint_num_states_mem;
 
-    matrix <T> mat_new_arg = mat_arg.mid(uint_l, mat_arg.size() - uint_l - 1);
+    matrix <T> mat_new_arg = mat_arg.mid(uint_l, sz_length - uint_l - 1);
 
-
-
-    ////matrix <T> mat_metric(uint_num_states, uint_num_stages + 1,std::numeric_limits<T>::max());
-    ////for (unsigned int uint_i = 0; uint_i < uint_num_states; uint_i++) mat_metric(uint_i, 0) = 0;
     matrix <T> mat_metric_past(uint_num_states, 1);
     matrix <T> mat_metric_next(uint_num_states, 1,std::numeric_limits<T>::max());
 
@@ -370,10 +367,12 @@ template <class T> matrix <T> channel <T>::decode_mlse(const matrix <T> &mat_arg
     T dbl_next_output;
     unsigned int uint_next_state;
 
-    for (unsigned int uint_stage = 0; uint_stage < uint_num_stages; uint_stage++) {
-        for (unsigned int uint_state = 0; uint_state < uint_num_states; uint_state++) {
-            for (unsigned int uint_pam_index = 0; uint_pam_index < uint_num_pam; uint_pam_index++) {
-
+    for (unsigned int uint_stage = 0; uint_stage < uint_num_stages; uint_stage++)
+    {
+        for (unsigned int uint_state = 0; uint_state < uint_num_states; uint_state++)
+        {
+            for (unsigned int uint_pam_index = 0; uint_pam_index < uint_num_pam; uint_pam_index++)
+            {
                 dbl_next_output = this->next_output(uint_state,uint_pam_index);
                 uint_next_state = this->next_state(uint_state,uint_pam_index);
 

test/channel.cpp

@@ -25,42 +25,18 @@
 
 int main(void)
 {
-
     // ignore the tail of the bits
     const unsigned len = 15;
 
-    susa::matrix<double> mat_bits(17,1);
-
     // the actual transmitted bits
-    mat_bits(0) = -1;
-    mat_bits(1) = -1;
-    mat_bits(2) = -1;
-    mat_bits(3) = -1;
-    mat_bits(4) = -1;
-    mat_bits(5) = 1;
-    mat_bits(6) = -1;
-    mat_bits(7) = 1;
-    mat_bits(8) = -1;
-    mat_bits(9) = 1;
-    mat_bits(10) = 1;
-    mat_bits(11) = -1;
-    mat_bits(12) = 1;
-    mat_bits(13) = -1;
-    mat_bits(14) = -1;
-    mat_bits(15) = 1;
-    mat_bits(16) = 1;
+    susa::matrix<double> mat_bits("-1 -1 -1 -1 1 1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1");
+    mat_bits.resize(18,1);
 
     // pulse amplitude (pam) vector
-    susa::matrix<double> mat_pam(2, 1);
-    mat_pam(0) = -1;
-    mat_pam(1) = 1;
+    susa::matrix<double> mat_pam("-1 1");
 
     // channel taps
-    susa::matrix<double> mat_taps(1, 4);
-    mat_taps(0) = 1;
-    mat_taps(1) = -0.9;
-    mat_taps(2) = 0.5;
-    mat_taps(3) = .4;
+    susa::matrix<double> mat_taps("1 -0.9 0.5 0.4");
 
     susa::channel<double> ch(mat_taps, mat_pam);
 
@@ -74,12 +50,11 @@ int main(void)
     {
         mat_decoded_bits(uint_i) = mat_decoded(uint_i) > 1 ? 1 : -1;
     }
-
-    //std::cout << "\ncoded : \n" << mat_coded;
-    //std::cout << "\nuncoded : \n" << mat_bits.left(len);
-    //std::cout << "\ndecoded : \n" << mat_decoded_bits.left(len);
+
+    susa::matrix <double> mat_decoded_mlse = ch.decode_mlse(mat_coded);
 
     SUSA_TEST_EQ(mat_bits.left(len), mat_decoded_bits.left(len), "BCJR channel equalizer.");
+    SUSA_TEST_EQ(mat_bits.left(len), mat_decoded_mlse.left(len), "MLSE (Viterbi) channel equalizer.");
     SUSA_TEST_PRINT_STATS();
 
     return (uint_failed);