Patent ID: 7073114
Filing Date: 2006-07-04
Classification: H03M

Abstract:
1. A method of decoding for parallel-concatenated convolutional codes that consist of at least two binary convolutional constituent subcodes of finite blocklength value and share a block of information-bits with respect to corresponding interleaver-orderings, so as to produce a block of said blocklength value decoded binary bits for the information-bits that are an approximation to decoded bits obtained from an iterative maximum a posteriori decoder when initially given code-bit channel-symbol values or quantized digital data representing channel-symbol values, wherein the decoding method is a procedure comprising the steps: (a) quantizing received code-bit channel-symbol values into digital data, (b) initializing by storing of digital data corresponding to code-bits into assigned memory locations as well as storing appropriate initialized digital data values at required locations including the memory locations that are shared by constituent subcodes to represent maximum a posteriori reliability estimates which are initialized to digital data representing equally likely estimates as also are the memory locations for extrinsic estimates and punctured code-bits, (c) applying of a recursive table-lookup decoding method for each constituent convolutional subcode while utilizing a set of pre-stored lookup tables and memory locations for each subcode, (d) applying more iterations of step (c) until a total of iterations has been completed, (e) extracting decoded binary estimates for the information-bits from the digital data at the shared memory locations representing the maximum a posteriori estimates by utilizing a most significant bit of the digital data, wherein the recursive table-lookup decoding method is a decoding method for a binary convolutional code of said finite blocklength value so as to produce: memory updated with digital data representing approximations for the maximum a posteriori reliability estimates for the number, equal to blocklength value, of information-bits; and memory updated with digital data representing approximations for the extrinsic reliability estimates for the number, equal to blocklength value of information-bits, wherein the decoding method is a recursive table-lookup procedure comprising the steps: (a) initializing by storing of data into memory, (b) reading data from the memory, (c) reading data from a set of pre-stored lookup tables, (d) storing data read from lookup tables into the memory, (e) incrementing a memory location-address pointer, when initially given memory stored with digital data representing: the channel-symbol reliability estimates for the number, equal to blocklength value, of parity-bits; previous extrinsic reliability estimates for the number, equal to blocklength value, of information-bits; and maximum a posteriori reliability estimates for the number, equal to blocklength value, of information-bits, which is a function of the previous extrinsic estimates, a priori estimates, and the channel-symbol estimates.