Parallel concatenated tail-biting convolutional code and decoder therefor

A method for decoding parallel concatenated convolutional codes, comprising the steps of:

• receiving from a channel a composite codeword that comprises a formatted collection of bits from a plurality (N) of component codewords that have been generated by applying tail-biting nonrecursive systematic convolutional codes to a block of data bits in a parallel concatenated encoder, forming received component codewords from the received composite codeword, each respective received component codeword being received by a corresponding one of a plurality of N component decoders of a composite decoder, each respective component decoder also receiving a set of a priori soft-decision information for vales of the data bits;
• decoding the received component codewords by a process of iterations through the N component decoders and N-1 interleavers to provide soft-decision outputs from the composite decoder, the N component decoders each providing soft-decision information on each data bit in the data block in the order encoded by the corresponding component encoder, the N-1 interleavers each interleaving the soft-decision information from a preceding component decoder to provide a permuted block of soft information to a subsequent component decoder, the set of a priori soft-decision information for the first of the N component decoders being calculated assuming that the data bits' values are equally likely for the first iteration and thereafter comprising a first function of the soft-decision information, which first function of the soft-decision information is fed back from the N.sup.th component decoder via a first deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the first deinterleaver being applied in reverse order to the N-1 interleavers, the set of a priori soft-decision information provided to each other component decoder comprising the first function of the soft-decision information from the previous sequential component decoder;
• and
• deinterleaving in a second deinterleaver to provide a second function of the soft-decision output from the N.sup.th component decoder as the composite decoder's soft-decision output using N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the second deinterleaver being applied in reverse order to the N-1 interleavers.

A method for encoding and decoding parallel concatenated convolutional codes, comprising the steps of:

• providing a block of data bits to a parallel concatenated encoder comprising a plurality of N component encoders and N-1 interleavers connected in a parallel concatenation;
• encoding the block of data bits in a first one of the component encoders by applying a tail-biting nonrecursive systematic convolutional code thereto and thereby generating a corresponding first component codeword comprising the data bits and parity bits;
• interleaving the block of data bits to provide a permuted block of data bits;
• encoding the resulting permuted block of data bits in a subsequent component encoder by applying a tail-biting nonrecursive systematic convolutional code thereto and thereby generating a corresponding second component codeword comprising the data bits and parity bits;
• repeating the steps of interleaving and encoding the resulting permuted block of data bits through the remaining N-2 interleavers and the remaining N-2 component encoders, and thereby generating component codewords comprising the data bits and parity bits;
• formatting the bits of the component codewords to provide a composite codeword;
• inputting the composite codeword to a channel;
• receiving a received composite codeword from a channel;
• forming received component codewords from the received composite codeword
• providing each respective received component codeword to a corresponding one of a plurality of N component decoders of a composite decoder, each respective component decoder also receiving a set of a priori probabilities for values of the data bits;
• decoding the received component codewords by a process of iterations through the N component decoders and N-1 interleavers to provide soft-decision outputs from the composite decoder, the N component decoders each providing soft-decision information on each data bit in the data block in the order encoded by the corresponding component encoder, the N-1 interleavers each interleaving the soft-decision information from a preceding component decoder to provide a permuted block of soft information to a subsequent component decoder, the set of a priori soft-decision information for the first of the N component decoders being calculated assuming that the data bits' values are equally likely for the first iteration and thereafter comprising a first function of the soft-decision information, which first function of the soft-decision information is fed back from the N.sup.th decoder via a first deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the first deinterleaver being applied in reverse order to the N-1 interleavers, the set of a priori soft-decision information provided to each other component decoder comprising the first function of the soft-decision information from the previous sequential component decoder;
• and
• deinterleaving in a second deinterleaver to provide a second function of the soft-decision output from the N.sup.th component decoder as the composite decoder's soft-decision output using N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the second deinterleaver being applied in reverse order to the N-1 interleavers.

A composite decoder for decoding parallel concatenated convolutional codes, comprising:

• a composite-codeword-to-component-codeword converter for receiving a composite codeword from a channel, the composite codeword comprising selected bits of a plurality of N component codewords that have been generated by applying tail-biting nonrecursive convolutional codes to a block of data bits in a parallel concatenated encoder, and forming a plurality of N corresponding received component codewords therefrom;
• a plurality (N) of component decoders, each respective decoder receiving a corresponding received component codeword from the composite-codeword-to-component-codeword converter, each respective decoder also receiving a set of a priori soft-decision information for values of the data bits, the N component decoders each providing soft-decision information on each data bit in the data block in the order encoded by a corresponding component encoder in the parallel concatenated encoder;
• a plurality of N-1 interleavers, each respective interleaver interleaving the soft-decision information from a corresponding component decoder to provide a permuted block of soft information to a subsequent component decoder, the received codewords being decoded by a process of iterations through the N component decoders and N-1 interleavers to provide soft-decision output from the composite decoder;,
• a first deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the first deinterleaver being applied in reverse order to the N-1 interleavers, the set of a priori soft-decision information for the first of the N component decoders being calculated assuming that the data bits' values are equally likely for the first iteration and thereafter comprising a first function of the soft-decision information, which first function of the soft-decision information is outputted by the N.sup.th decoder and fed back via the first deinterleaver, the set of a priori soft-decision information provided to each other component decoder comprising the first function of the soft-decision information from the previous sequential component decoder;
• and
• a second deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the second deinterleaver being applied in reverse order to the N-1 interleavers, the second deinterleaver deinterleaving a second function of the soft-decision output from the N.sup.th component decoder to provide the composite decoder's soft-decision output.

An encoder and decoder system for encoding and decoding parallel concatenated convolutional codes, comprising:

• a parallel concatenated encoder comprising a plurality (N) of component encoders and a plurality (N-1) of encoder interleavers connected in a parallel concatenation for systematically applying tail-biting nonrecursive systematic convolutional codes to a block of data bits and various permutations of the block of data bits, and thereby generating component codewords comprising the data bits and parity bits;
• and
• a composite codeword formatter for formatting the collection of bits from the component codewords to provide a composite codeword;
• a composite-codeword-to-component-codeword converter for receiving the composite codeword from a channel and forming a plurality of N corresponding received component codewords therefrom;
• a plurality (N) of component decoders, each respective decoder receiving a corresponding received component codeword from the composite-codeword-to-component-codeword converter, each respective decoder also receiving a set of a priori soft-decision information for values of the data bits, the N component decoders each providing soft-decision information on each data bit in the data block in the order encoded by a corresponding component encoder in the parallel concatenated encoder;
• a plurality of N-1 interleavers, each respective interleaver interleaving the soft-decision information from a corresponding component decoder to provide a permuted block of soft information to a subsequent component decoder, the received codewords being decoded by a process of iterations through the N component decoders and N-1 interleavers to provide soft-decision output from the composite decoder;
• a first deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the first deinterleaver being applied in reverse order to the N-1 interleavers, the set of a priori soft-decision information for the first of the N component decoders being calculated assuming that the data bits' values are equally likely for the first iteration and thereafter comprising a first function of the soft-decision information, which first function of the soft-decision information is outputted by the N.sup.th decoder and fed back via the first deinterleaver, the set of a priori soft-decision information provided to each other component decoder comprising the first function of the soft-decision information from the previous sequential component decoder;
• and
• a second deinterleaver comprising N-1 deinterleavers corresponding to the N-1 interleavers, the N-1 deinterleavers of the second deinterleaver being applied in reverse order to the N-1 interleavers, the second deinterleaver deinterleaving a second function of the soft-decision output from the N.sup.th component decoder to provide the composite decoder's soft-decision output.