Changeset 4147

Timestamp:

06/11/07 18:51:18 (6 years ago)

Author:

hvolos

Message:

Added the convolutional code to SigProc?

Location:

SigProc/trunk/SigProc

Files:

• Makefile.am (modified) (1 diff)
• SigProc.h (modified) (5 diffs)
• fec_conv.cpp (added)

SigProc/trunk/SigProc/Makefile.am

@@ -6 +6 @@
     sources.cpp                     \
     utility.cpp                     \
+    fec_conv.cpp                    \
     fixed.c                         \
     modem.cpp

SigProc/trunk/SigProc/SigProc.h

@@ -34 +34 @@
 
 namespace SigProc {
+//-----------------------------------------------------------------------------
+//
+// Convolutional coding definitions
+//
+//-----------------------------------------------------------------------------
+
+/** \brief Defines the basic entry for building the trellis at the decoder
+*/
+class TrellisEntry{
+    public:
+        unsigned int previousState; ///< The state prior to the current state, used for tracing back the trellis
+        unsigned short int symbolNo; ///< The symbol that caused the change of state to the currrent state
+        signed int distance; ///< The total distance of the current state
+};
+
+/** \brief Includes all the necessary information for encoding and decoding the symbols
+ *
+ * The contructor has to be ALWAYS be used. The generator polynomials for each code rate have to be specified in DECIMAL, not OCTAL format
+ *
+ * For more information for the meaning of the symbols used and for generator polynomials look at
+ * Proakis Digital Communications book 4th Edition, pages 471 & 492 respectively.
+*/
+class trellisTable{
+    public:
+        /// The contructor has to be always used
+        trellisTable(unsigned int * generatorPolynomials, unsigned short int k, unsigned short int n, unsigned short K);
+
+        /// =The destructor
+        ~trellisTable();
+
+        unsigned short int k;///<the input bits at a time
+        unsigned short int n;///< the output bits at a time
+        unsigned short int K;///<the contraint length
+        unsigned short int numberOfInputStates;///< Based on k, how many different input states exist
+        unsigned int numberOfTrellisStates;///<Number of different trellis states, defined by k & K
+
+        unsigned int **output; ///< The rows are the trellis states and the columns the symbols, gives the output given the current state and symbol.
+        unsigned int **nextState;///< The sane as output, gives the the next state given the current state and synbol
+
+    protected:
+        ///Generates the trellis table given the generator polynomials in DECIMAL not OCTAL
+        void GenerateTrellisTable(unsigned int * generatorPolynomials);
+
+        ///Peforms modulo 2 addition to the bits of the input number (symbol)
+        unsigned short int Modulo2BitWiseAdd(unsigned short int inputNumber);
+};
+
+/** \brief Defines the basic functionality for the convolution encoding/decoding
+*/
+
+class fec_conv{
+    public:
+        /// It accepts the pointer to the trellis Table
+        void SetTrellisTable(trellisTable *theTrellisTableIn);
+
+    protected:
+        /// It converts a decimal numnber (symbol) into a vector of bits
+        void Dec2Bin(unsigned int decNumber,unsigned short int * outputData,unsigned short int numberOfBits);
+
+        trellisTable * theTrellisTable;///< It holds the trellis table used for encoding/decoding
+};
+
+/** \brief It defines the encoding functionality
+ *
+ * To use this class, first pass the trellis table pointer
+ *
+ * To encode: reset the state, feed data & get encoded data, repeat for the next packet.
+ *
+ * To make the encoder to return at the zero state during encoding, feed K 0 symbols after the encoding of the data is done.
+*/
+class fec_conv_encoder : public fec_conv{
+    public:
+        ///Default constructor
+        fec_conv_encoder();
+
+        ///Default destructor
+        ~fec_conv_encoder();
+
+        /// Resets the state of the encoder to the zero state
+        void ResetState();
+
+        ///It gets the current state of the encoder
+        unsigned int GetState();
+
+        ///It accepts a vector of k bits and returns a vector of n bits
+        void Encode(unsigned short int * inputData,unsigned short int * outputData);
+
+    protected:
+        unsigned int currentState;///<The current state of the encoder
+};
+
+/** \brief It defines the decoding functionality
+ *
+ * The following cycle should be followed to use this class:
+ *
+ * 1. Set the trellis table
+ *
+ * 2. Set the traceback length
+ *
+ * 3. Set mode
+ *
+ * 4. Feed symbols into the decoder
+ *
+ * 5. Trace back trellis
+ *
+ * 6. Get the decoded symbols
+ *
+ * 7. Reset and repeat from 4 for the next packet. If the decoding parameters change, might need to repeat from 1.
+*/
+class fec_conv_decoder:public fec_conv {
+    public:
+        ///Default contructor
+        fec_conv_decoder();
+
+        ///Default destructor
+        ~fec_conv_decoder();
+
+        /// Set the numbers of the input symbols to be decoded, this equals to the total bits on the output of the encoder divided by k
+        void SetNoOfSymbols2TraceBack(unsigned int tracebackLength);
+
+        /// Feeds a symbol (in a vector of n bits) at time for decoding
+        void Symbol2Decode(unsigned short int * inputData);
+
+        /// After all symbols were fed in the decoder, it will tracesback the trellis to the begining.
+        void TraceBackTrellis();
+
+        ///After the trellis was traced back, it returns a decoded symbol, starting from the beggining each time is called.
+        void GetDecodedSymbol(unsigned short int * outputData);
+
+        ///It resets the state of the decoder in order to be able to start a new decoding session
+        void Reset();
+
+        ///Sets the mode of the decoder 0: the encoded data start from zero state 1: the encoded data start from the the zero state and end at the zero state.
+        void SetMode(unsigned short int mode);
+
+    protected:
+        ///Calculates the distance between the input bits (symbol) to the current trellis symbol
+        signed int CalculateDistance(unsigned short int inBits, unsigned short int symbol);
+
+        unsigned int currentTrellisIndex;///<The current trellis stage used when building and tracing back the trellis.
+        unsigned int decodedSymbolIndex;///<The next symbol to be returned when the GetDecodedSymbol is called.
+        unsigned int noOfSymbols2TraceBack;///<Number of symbols to trace back, should be equal to the symbols used in the encoding process.
+        unsigned int mode;///<The mode of the encoder
+
+        unsigned int *tracedBackSymbols;///<A vector array with the symbols traced back
+        TrellisEntry **theTrellis; ///<A two dimensional array making the trellis, states are rows, and columns are each trellis stage.
+};
 
 //-----------------------------------------------------------------------------
@@ -132 +279 @@
     /// if buffer is full
     void Push(T _value) {
-        
+
         // OK to push value
         headPtr[i_head++] = _value;
-        
+
         // Ensure head index does not equal or exceed bufferSize (wrap)
         i_head = i_head % bufferSize;
@@ -293 +440 @@
             float & _gmin,
             float & _gmax);
-    
+
     /// Get status
     void GetStatus(float & _gain, float & _energy);
-    
+
     /// track signal energy and apply gain (real)
     void ApplyGain(short & I);
@@ -346 +493 @@
  public:
     phase_detect(float scale_factor);
- 
+
     void do_work(short I_in, short Q_in, short I_nco, short Q_nco, short &out);
 
@@ -785 +932 @@
 
 }
-
 #endif
+
+