Convolutional FEC codes are very popular because of their powerful error correction capability and are especially suited for correcting random errors. The most effective decoding method for these codes is the soft decision Viterbi algorithm. ntVIT core is a high performance, fully configurable convolutional FEC core, comprised of a 1/N convolutional encoder, a variable code rate puncturer/depuncturer and a soft input Viterbi decoder. Depending on the application, the core can be configured for specific code parameters requirements. The highly configurable architecture makes it ideal for a wide range of applications. The convolutional encoder maps 1 input bit to N encoded bits, to generate a rate 1/N encoded bitstream. A puncturer can be optionally used to derive higher code rates from the 1/N mother code rate. On the encoder side, the puncturer deletes certain number of bits in the encoded data stream according to a user defined puncturing pattern which indicates the deleting bit positions. On the decoder side, the depuncturer inserts a-priori-known data at the positions and flags to the Viterbi decoder these bits positions as erasures. The Viterbi decoder uses a maximum-likelihood detection recursive process to cor-rect errors in the data stream. The Viterbi input data stream can be composed of hard or soft bits. Soft decision achieves a 2 to 3dB in-crease in coding gain over hard-decision decoding. Data can be received continuously or with gaps.
