3. Decoding

3.1 Algorithms for decoding convolutional codes

Convolutional codes: first, let's take a look at convolutional codes. We're only interested here in the case of systematic recursive convolutional codes. An encoder for the systematic recursive code (15/17) is shown in figure 7 . The data to be encoded X _i enter the encoder from the left. The encoder has three internal flip-flops. At time i, the encoder calculates two binary values R _i and n _i according to the following equations: