Patent FR-2822316-A1 (FR)
Title: Method and device for resources-constrained optimization of the size of coded data blocks, for use in advanced telecommunication systems
Inventor: GUEGUEN ARNAUD
IPC: H03M13/35
Filed: 2001-03-19
Abstract: The method for optimizing the size of coded data blocks to be subjected to an iterative decoding process comprises the first step for evaluating an available resource for decoding a block of current size (N), and the second step for searching among a set of block sizes (N/k) for sub-multiples of the current size given by an integer factor (k) which is greater than or equal to 1, and which necessitates an average number of iterations compatible with the available resource, so to obtain a lower rate of output errors in the iterative decoding. The available resource is a time (T) or an energy available for receiving all the data of a block and for effecting the iterative decoding.  The data are interleaved by an interleaver channel, and the available resource is used for obtaining the data of a block in de-interleaved form and for effecting the iterative decoding on de-interleaved data. A maximum number of iterations compatible with the available resource is also determined for the size of current block at the first step. A minimum or required number of iterations (nreq) which effects the iterative decoding is estimated as a function of the maximum rate of errors for the size of current block and the signal-to-noise or the carrier/noise (C/N) ratio. The second step is not effected if the maximum number of iterations exceeds the minimum number. The size of block and the highest maximum number of iterations associated with the size are selected at the second step giving the average number of iterations compatible with the available resource; the optimal size allowing the lowest rate of output errors is found by searching among the si zes of selected sub-multiples. The iterations are terminated when a predetermined reliability criterion is satisfied, or when the number of iterations attains the maximum number. The average numbers of iterations for different sizes of sub-multiples, different maximum numbers of iterations and different signal-to-noise ratios are stored in a table, and the table is updated as the iterative decoding progresses. The average numbers of iterations are obtained by interpolation on the basis of values available in the table. The data of a block of initial size are coded as a sequence of sub-blocks of optimal size, and the sub-blocks are decoded one by one by a succession of iterations of the iterative decoding, or the sub-blocks are decoded by effecting successively on each sub-block an iteration of the iterative decoding. A device for iterative decoding of data blocks coded by a turbo-coder comprises means for implementing the optimization method which include means for transmitting to th e turbo-coder an information on the optimal size of block. A system for coding/decoding comprises a turbo-coder adapted to coding the blocks of data and the device for iterative decoding which comprises means for receiving the information on the optimal size of block and for modifying the size of at least one internal interleaver as a function of received information. A device for coding data block comprises means for implementing the optimization method which include means for adaptively modifying the size of coded data blocks as a function of the optimal block size. A device for turbo-equilization of data blocks coded by a coder and modulated comprises means for implementing the optimization method which include means for transmitting to the coder the information on the optimal block size.