This dissertation develops a set of new algorithms for soft decision decoding of binary linear block codes. The performance (i.e. the probability of error) of these algorithms is asymptotically optimum for high signal-to-noise ratio for binary linear block codes transmitted over the additive white gaussian (AWGN) channel using antipodal signalling.
Among the algorithms proposed are the generalized Chase algorithms. In contrast to Chase algorithms, which require a {(d-1)/2} hard error-correcting decoder for decoding a binary linear block code of minimum distance d, the generalized Chase algorithms can use a binary decoder that can correct less than {(d-1)/2} hard errors. The Chase algorithms are particular cases of the generalized Chase algorithms. Modified generalized Chase algorithm 2 and 3 are proposed for codes that have an overall parity check. These algorithms use fewer test patterns than the generalized Chase algorithms and they also have asymptotically optimum performance for high signal-to-noise ratio.
The erasure information decoding algorithm of Tanaka and Kakigahara is generalized so that any hard decoder that corrects only up to t errors, 0 (LESSTHEQ) t (LESSTHEQ) {(d-1)/2} can be used to obtain asymptotically optimal performance for high signal-to-noise ratio. The modified erasure information decoding algorithm is proposed for codes that have an overall parity check. The modified erasure information decoding algorithm requires fewer test patterns than the erasure information decoding algorithm and its performance is also asymptotically optimum for high signal-to-noise ratio.
The algorithms proposed by Dorsch and, Baumert and McEliece are analyzed to determine the conditions under which their performance would be asymptotically optimum for high signal-to-noise ratio.
Simulation results for the (47,23) Quadratic Residue code are shown to demonstrate the performance of the algorithms. The results indicate that even for low signal-to-noise ratio the performance of a maximum likelihood decoder can be approached by a relatively simple decoding procedure.
This dissertation develops a set of new algorithms for soft decision decoding of binary linear block codes. The performance (i.e. the probability of error) of these algorithms is asymptotically optimum for high signal-to-noise ratio for binary linear block codes transmitted over the additive white gaussian (AWGN) channel using antipodal signalling.
Among the algorithms proposed are the generalized Chase algorithms. In contrast to Chase algorithms, which require a {(d-1)/2} hard error-correcting decoder for decoding a binary linear block code of minimum distance d, the generalized Chase algorithms can use a binary decoder that can correct less than {(d-1)/2} hard errors. The Chase algorithms are particular cases of the generalized Chase algorithms. Modified generalized Chase algorithm 2 and 3 are proposed for codes that have an overall parity check. These algorithms use fewer test patterns than the generalized Chase algorithms and they also have asymptotically optimum performance for high signal-to-noise ratio.
The erasure information decoding algorithm of Tanaka and Kakigahara is generalized so that any hard decoder that corrects only up to t errors, 0 (LESSTHEQ) t (LESSTHEQ) {(d-1)/2} can be used to obtain asymptotically optimal performance for high signal-to-noise ratio. The modified erasure information decoding algorithm is proposed for codes that have an overall parity check. The modified erasure information decoding algorithm requires fewer test patterns than the erasure information decoding algorithm and its performance is also asymptotically optimum for high signal-to-noise ratio.
The algorithms proposed by Dorsch and, Baumert and McEliece are analyzed to determine the conditions under which their performance would be asymptotically optimum for high signal-to-noise ratio.
Simulation results for the (47,23) Quadratic Residue code are shown to demonstrate the performance of the algorithms. The results indicate that even for low signal-to-noise ratio the performance of a maximum likelihood decoder can be approached by a relatively simple decoding procedure.
Soft decision decoding of binary linear block codes transmitted over the additive white Gaussian channel (AWGN) using antipodal signaling is considered. A set of decoding algorithms called generalized Chase algorithms is proposed. In contrast to Chase algorithms, which require a\lfloor (d- 1)/2 \rfloorbinary error-correcting decoder for decoding a binary linear block code of minimum distanced, the generalized Chase algorithms can use a binary decoder that can correct less than\lfloor ( d - 1)/2 \rfloorhard errors. The Chase algorithms are particular cases of the generalized Chase algorithms. The performance of all proposed algorithms is asymptotically optimum for high signal-to-noise ratio (SNR). Simulation results for the(47, 23)quadratic residue code indicate that even for low SNR the performance level of a maximum likelihood decoder can be approached by a relatively simple decoding procedure.
The generalized minimum distance (GMD) and Chase (1972) decoding algorithms are some of the most important suboptimum bounded distance decoding algorithms for binary linear block codes over an additive white Gaussian noise (AWGN) channel. We compute the limitation of the ratio between the probability of decoding error for the GMD or any one of the Chase decoding algorithms and that of the maximum-likelihood (ML) decoding when the signal-to-noise ratio (SNR) approaches infinity. If the minimum Hamming distance of the code is greater than 2, the limitation is shown to be equal to 1 and thus the GMD and Chase decoding algorithms are asymptotically optimum.
This dissertation deals with maximum-likelihood soft-decision decoding as well as suboptimal soft-decision decoding of linear block codes. We present three new decoding algorithms: $MA\sp*D,\ H\sp*,$ and Directed Search. The first algorithm, $MA\sp*D,$ is an instance of Algorithm $A\sp*$ that conducts heuristic search through a code tree of the transmitted code when the decoding problem is transformed into a problem of graph-search through a code tree. $MA\sp*D$ takes into consideration more properties of the code and is considerably more efficient than the original $A\sp*$ decoding algorithm presented by Han, Hartmann, and Chen in 1993. The second algorithm, $H\sp*,$ is a new decoding algorithm that determines the value of every component of a minimum-cost codeword by estimating the cost of the minimum-cost codeword, which has a fixed value at one of the k most reliable, linearly independent bit positions. The suboptimal version of this algorithm is combined with other decoding algorithms to reduce the search space during the decoding process. The third algorithm, Directed Search, is designed to enhance the performance of soft-decision decoding by searching in continuous space. This approach explores the search space between a given vector and the received vector and finds the codeword closest to the received vector in the space explored. We also present a novel and efficient hybrid decoding algorithm for (n, k) linear block codes. It hybridizes $MA\sp*D,\ H\sp*,$ and Directed Search algorithms, utilizing their strengths to make the decoding more efficient. Simulation results for this hybrid algorithm are presented for the (104,52) binary-extended quadratic residue code and for the (128,64), the (256, 131), and the (256, 139) binary-extended BCH codes. This hybrid algorithm can efficiently decode the (104,52) binary extended quadratic residue code and the (128,64) code for any signal-to-noise ratio and has near-optimal to optimal performance. Previously, no practical decoder could decode these two codes with such a performance for all signal-to-noise ratio ranges.
This dissertation presents a novel approach to soft decision decoding for binary linear block codes. The basic idea of this approach is to achieve a desired error performance progressively in a number of stages. For each decoding stage, the error performance is highly bounded and the decoding is terminated at the stage where either near-optimum error performance or a desired level of error performance is achieved. As a result, more flexibility in the trade-off between performance and decoding complexity is provided. The proposed decoding is based on the reordering of the received symbols according to their reliability measure. In the dissertation, we evaluate the statistics of the noise after ordering. Based on these statistics, we derive two monotonic properties which dictate the reprocessing strategy. Each codeword is decoded in two steps: (1) hard-decision decoding based on reliability information and (2) reprocessing of the hard-decision decoded codeword in successive stages until the desired performance is achieved. The reprocessing is based on the monotonic properties of the ordering and is carried out using a cost function. A new resource test highly related to the reprocessing strategy is introduced to reduce the number of computations for each reprocessing stage. For short codes of lengths N ≤ 32 or medium codes with 32 < N ≤ 64 with rate R ≥ 0.6, near-optimum bit error performance is achieved in two stages of reprocessing with at most a computation complexity of o(K2) constructed code-words, where K is the dimension of the code. For longer codes, three or more reprocessing stages are required to achieve near-optimum decoding. However, most of the coding gain is obtained within the first two reprocessing stages for error performances of practical interest. The proposed decoding algorithm applies to any binary linear code, does not require any data storage and is well suitable for parallel processing. Furthermore, the maximum number of computations required at each reprocessing stage is fixed, which prevents buffer overflow at low SNR. Further reductions of the number of computations based on probabilistic or decomposable properties of the code considered are also investigated. The generalization of the algorithm to other channels is discussed. Finally, the discrete time channel associated with the AWGN model after ordering is greatly simplified. This simplification allows an important reduction of the number of computations required to evaluate the theoretical error performance of any algorithm based on a partial or total ordering.
In this correspondence, we consider the decoding of binary block codes over the additive white Gaussian noise (AWGN) channel with binary phase-shift keying (BPSK) signaling. By a reliability-order-based decoding algorithm (ROBDA), we mean a soft-decision decoding algorithm which decodes to the best (most likely) codeword of the form that is the sum of the hard-decision tuple and an error pattern in a set determined only by the order of the reliabilities of the hard decisions. Examples of ROBDAs include many well-known decoding algorithms, such as the generalized-minimum-distance (GMD) decoding algorithm, Chase decoding algorithms, and the reliability-based decoding algorithms proposed by Fossorier and Lin. It is known that the squared error-correction-radii of ROBDAs can be computed from the minimal squared Euclidean distances (MSEDs) between the all-one sequence and the polyhedra corresponding to the error patterns. For the computation of such MSEDs, we give a new method which is more compact than the one proposed by Fossorier and Lin. These results are further used to show that any bounded-distance ROBDA is asymptotically optimal: The ratio between the probability of decoding error of a bounded-distance ROBDA and that of the maximum-likelihood (ML) decoding approaches 1 when the signal-to-noise ratio (SNR) approaches infinity, provided that the minimum Hamming distance of the code is greater than 2.
A non-soft decision decoding algorithm for binary linear block codes transmitted over AWGN channel is presented. Unlike soft decision decoding algorithms, the proposed algorithm does not computing weighted Hamming distances. Based on the majority of code word candidates from the hard decision decoding output, the proposed algorithm improves error-correcting performance by 1 dB of coding gain compared to that of hard decision decoding algorithms. Also, a schematic block diagram for finding the codeword of majority is developed. Furthermore, a comparison of hardware complexity is made between the computation of weighted Hamming distances and the finding of majority code word.