Development of a variable rate syndrome sequential decoder based on a stack algorithm

The design of a soft decision variable rate sequential decoder using a modified stack algorithm is described. The feedback systematic convolutional code is used for encoding, and a syndrome decoding method is used for decoding. The stack decoder searches the most likely paths using the syndrome sequence, which is formed by a syndrome former. A dummy-bit-insertion technique permits effective decoding of high-rate codes, such as R=3/4 and 7/8. It is concluded that since this stack decoder provides a coding gain much higher than the conventional Viterbi decoder, its application to power-limited satellite or space communication systems will make it possible to use transmission power more efficiently and/or to improve the transmission quality