Error-correcting coding has become one integral part in nearly all the modern data transmission and storage systems. Due to the powerful error-correcting capability, Reed-Solomon (RS) codes are among the most extensively used error-correcting codes with applications in wireless communications, deep-space probing, magnetic and optical recording, and digital television. Traditional hard-decision decoding (HDD) algorithms of RS codes can correct as many symbol errors as half the minimum distance of the code. Recently, much attention has been paid to algebraic soft-decision decoding (ASD) algorithms of RS codes. These algorithms incorporate channel probabilities into an algebraic interpolation process. As a result, significant coding gain can be achieved with a complexity that is polynomial in codeword length. Practical ASD algorithms include the Koetter-Vardy, low-complexity Chase (LCC) and bit-level generalized minimum distance (BGMD) decodings. This book focuses on the design of efficient VLSI architectures for ASD decoders.

Algebraic soft-decision decoding (ASD) algorithms of Reed-Solomon (RS) codes have attracted much interest due to their significant coding gain and polynomial complexity. Practical ASD algorithms include the Koetter-Vardy, low-complexity Chase (LCC) and bit-level generalized minimum distance (BGMD) decodings. This thesis focuses on the design of efficient VLSI architectures for ASD decoders. One major step of ASD algorithms is the interpolation. Available interpolation algorithms can only add interpolation points or increase interpolation multiplicities. However, backward interpolation, which eliminates interpolation points or reduces multiplicities, is indispensable to enable the re-using of interpolation results. In this thesis, a novel backward interpolation is first proposed for the LCC decoding through constructing equivalent Grbner bases. In the LCC decoding, 2 test vectors need to be interpolated over. With backward interpolation, the interpolation result for each of the second and later test vectors can be computed by only one backward and one forward interpolation iterations. Compared to the previous design, the proposed backward-forward interpolation scheme can lead to significant memory saving. To reduce the interpolation latency of the LCC decoding, a unified backward-forward interpolation is proposed to carry out both interpolations in a single iteration. With only 40percent area overhead, the proposed unified interpolation architecture can almost double the throughput when large is adopted. Moreover, a reduced-complexity multi-interpolator scheme is developed for the low-latency LCC decoding. The proposed backward interpolation is further extended to the iterative BGMD decoding. By reusing the interpolation results, at least 40 percent of the interpolation iterations can be saved for a (255, 239) code while the area overhead is small. Further speedup of the BGMD interpolation is limited by the inherent serial nature of the interpolation algorithm. In this thesis, a novel interpolation scheme that can combine multiple interpolation iterations is developed. Efficient architectures are presented to integrate the combined and backward interpolation techniques. A combined-backward interpolator of a (255, 239) code is implemented and can achieve a throughput of 440 Mbps on a Xilinx XC2V4000 FPGA device. Compared to the previous fastest implementation, our implementation can achieve a speedup of 64percent with 51percent less FPGA resource. The factorization is another major step of ASD algorithms. In the re-encoded LCC decoding, it is proved that the factorization step can be eliminated. Hence, the LCC decoder can be further simplified. In the reencoded ASD decoders, a re-encoder and an erasure decoder need to be added. These two blocks can take a significant proportion of the overall decoder area and may limit the achievable throughput. An efficient re-encoder design is proposed by computing the erasure locator and evaluator through direct multiplications and reformulating other involved computations. When applied to a (255, 239) code, our re-encoder can achieve 82percent higher throughput than the previous design with 11percent less area. With minor modifications, the proposed design can also be used to implement erasure decoder. After applying available complexity-reducing techniques, complexity comparisons for three practical ASD decoders were carried out. It is derived that the LCC decoder can achieve similar or higher coding gain with lower complexity for high-rate codes. This thesis also provides discussions on how the hardware complexities of ASD decoders change with codeword length, code rate and other parameters.

A divide-and-conquer approach to perform the bivariate polynomial interpolation procedure is discussed in Chapter 3. This method can potentially reduce the interpolation complexity of algebraic soft-decision decoding of Reed-Solomon code.

This monograph is a thoroughly revised and extended version of the author's PhD thesis, which was selected as the winning thesis of the 2002 ACM Doctoral Dissertation Competition. Venkatesan Guruswami did his PhD work at the MIT with Madhu Sudan as thesis adviser. Starting with the seminal work of Shannon and Hamming, coding theory has generated a rich theory of error-correcting codes. This theory has traditionally gone hand in hand with the algorithmic theory of decoding that tackles the problem of recovering from the transmission errors efficiently. This book presents some spectacular new results in the area of decoding algorithms for error-correcting codes. Specificially, it shows how the notion of list-decoding can be applied to recover from far more errors, for a wide variety of error-correcting codes, than achievable before The style of the exposition is crisp and the enormous amount of information on combinatorial results, polynomial time list decoding algorithms, and applications is presented in well structured form.