A new decoder is proposed to decode the (24, 12, 8) binary extended Golay code up to four errors. It consists of the conventional hard decoder for correcting up to three errors, the detection algorithm for four errors and the soft decoding for four errors. For a weight-4 error in a received 24-bit word, Method 1 or 2 is developed to determine all six possible error patterns. The emblematic probability value of each error pattern is then defined as the product of four individual bit-error probabilities corresponding to the locations of the four errors. The most likely one among these six error patterns is obtained by choosing the maximum of the emblematic probability values of all possible error patterns. Finally, simulation results of this decoder in additive white Gaussian noise show that at least 93% and 99% of weight-4 error patterns that occur are corrected if the two Eb/N0 ratios are greater than 2 and 5 dB, respectively. Consequently, the proposed method can achieve a better percentage of successful decoding for four errors at variable signal-to-noise ratios than Lu et al.'s algorithm in software. However, the speed of the method is slower than Lu et al.'s algorithm.

A new algorithm is developed to facilitate faster decoding of the (47,24,11) quadratic residue (QR) code. This decoder, based on the idea first developed by Reed in a 1959 MIT Lincoln Laboratory Report, uses real channel data to estimate the individual bit-error probabilities in a received word. The algorithm then sequentially inverts the bits with the highest probability of error until one of the errors is canceled. The remaining errors are then corrected by the use of algebraic decoding techniques. This new algorithm, called the reliability-search algorithm, is a complete decoder that significantly reduces the decoding complexity in terms of CPU time while maintaining the same bit-error rate (BER) performance. In fact, this algorithm is an appropriate modification to the algorithm developed by Chase.

The (23,12,7) Golay code is a perfect linear error-correcting code that can correct all patterns of three or fewer errors in 23 bit positions. A simple BCH decoding algorithm, given in E. Berlekamp (1968), can decode the (23,12,7) Golay code provided there are no more than two errors. The shift-search algorithm, developed by Reed et a. (1990), sequentially inverts the information bits until the third error is canceled. It then utilizes the BCH decoding algorithm to correct the remaining two errors. In this paper a simplified decoding algorithm, called the reliability-search algorithm, is proposed. This algorithm uses bit-error probability estimates to cancel the third error and then uses the BCH decoding algorithm to correct the remaining two errors. Simulation results show that this new algorithm significantly reduces the decoding complexity for correcting the third error while maintaining the same BER performance.