Convolutional encoding and Viterbi decoding using the DSP56001

Abstract

Digital signal processors began their life like the laser — an invention in search of applications. Of course, digital signal processors were originally designed for applications such as low-pass filtering which could not be accomplished by conventional microprocessors. As DSP has become more widespread, the range of applications has increased. This application note describes the use of digital signal processors in convolutional encoding and decoding. Convolutional encoding provides an improved way of transmitting data at high speeds over noisy channels. Its use has been limited by the need to carry out the high-speed realtime operations required by convolutional encoders/decoders. The new digital signal processors now make it possible to implement systems that require very large numbers of simple (e.g. shifting and adding, exclusive or, etc.) high-speed computations. This application note looks at both the theory of the Viterbi (or trellis) convolutional encoder/decoder and its implementation.