This paper is concerned with the evaluation of the block error probability of maximum likelihood decoding (MLD) for a block code or a block modulation code over an AWGN channel. It is infeasible to evaluate the block error probability of MLD for a long block code with a large minimum distance by simulation. In this paper, a new evaluation method of the block error probability of MLD by an analytical method combined with simulation with a low-weight sub-trellis diagram is proposed. We show that this proposed method gives a tighter upper bound on the block error probability than the conventional one, and can be applicable to a relatively long block code with a large minimum distance for which conventional simulation is infeasible.

This paper describes relation between the number of library pairs and error probability to have all the pairs as fixed points for second-order bidirectional associative memory (BAM). To estimate accurate error probability, three methods have been compared; (a) Gaussian approximation, (b) characteristic function method, and (c) Hermite Gaussian approximation (proposed by this paper). Comparison shows that Gaussian approximation is valid for the larger numbers of neurons in both two layers than 1000. While Hermite Gaussian approximation is applicable for the larger number of neurons than 30 when Hermite polynomials up to 8th are considered. Capacity of second-order BAM at the fixed error probability is estimated as the function of the number of neurons.

Error locating codes were first presented in 1963 by J.K. Wolf and B.Elspas. Since then several code design methods have been proposed. However, their algebraic structure has not yet been clarified. It is apparent that necessary and sufficient conditions for error correcting/detecting codes can be expressed by Hamming distance, but, on the other hand, those for error locating codes cannot always be expressed only by Hamming distance. This paper presents necessary and sufficient conditions for error locating codes by using a newly defined metric and a function. The function represents the number of bytes where Hamming distance between corresponding bytes of two codewords has a certain integer range. These conditions show that an error locating code having special code parameters is an error correcting/detecting code. This concludes that error locating codes include existing bit/byte error correcting/detecting codes in their special cases.

In this paper a new class of single error-correcting fixed block-length (d, k) codes has been proposed. The correctable error types are peak-shift error, insertion or deletion error, symmetric error, etc. The basic technique to construct codes is a systematic construction algorithm of multilevel sequences with a constant Lee weight (TALG algorithm). The coding rate and efficiency are considerably good, and hence the proposed new codes will be very useful for improving the reliability of high density magnetic recording.

This paper proposes a new speech codec based on CELP for PHS multimedia communication. PHS portable terminals should consume as little power as possible, and the codec used in them has to be robust against channel errors. Therefore, the proposed codec operates with low computational complexity while reducing the deterioration in speech quality due to channel errors. This codec uses two new schemes to reduce computational complexity. One is moving average scalar quantization for the filter coefficients of the synthesis filter. This scheme requires 90% less complexity to quantize synthesis filter coefficients compared to the widely used vector quantization. The other is pre-selection for selecting an algebraic codebook used as random excitation source. An orthogonalization scheme is used for stable pre-selection. Deterioration of speech quality is suppressed by using CRC and parameter estimation for error protection. Two types of codec are proposed: a 10-ms frame type that transmits 160 bits every 10-ms and a 15-ms frame type that transmits 160 bits every 15 ms. The computational complexity of these codecs is less than 5 MOPS. In a nochannel error environment, the speech quality is equal to that of ITU-TG.726 at 32.0 kbit/s. With 0.3% channel error, both codecs offer more comfortable conversation than G.726. Moreover, at 1.0% channel error, the 10-ms frame type still provides comfortable conversation.

This paper presents an event-driven approach to the timing verification of latch-synchronized systems. The proposed method performs critical path extraction and timing error detection at the same time, and extracts the critical path only if necessary. By doing so, the complexity of analysis is reduced and efficiency is greatly improved over the conventional approaches which detect timing errors after extracting the complete critical paths of the system. Experimental results show that, compared to the existing methods, it provides a more than 12-fold improvement in speed on the average for ISCAS benchmark circuits, and the relative efficiency of analysis improves as the circuit size grows.

In this paper, we present an error concealment method to recover damaged blocks for block-based image coding schemes. Imperfect transmission of image data results in damaged blocks in the reconstructed images. Hence recovering damaged image blocks is needed for reliable image communications. To recover damaged blocks is to estimate damaged blocks from the correctly received or undamaged neighborhood information with a priori knowledge about natural images. The recovery problem considered in our method is to estimate a larger block, which consists of a damaged block and the undamaged neighborhood, from the undamaged neighborhood. To find an accurate estimate, a set of the feature vectors is introduced and an estimate is expressed as a linear combination of the feature vectors. The proposed method recoveres damaged blocks by projecting the undamaged neighborhood information onto the feature vectors. The sequential projections onto the feature vectors algorithm is proposed to find the projection coefficients of the feature vectors to minimize the squared difference of an estimate and the undamaged neighborhood information. We tested our algorithm through computer simulations. The experimental results showed the proposed method ourperforms the frequency domain prediction method in the PSNR values by 4.0-5.0dB. Tthe reconstructed images by the proposed method provide a good subjective quality as well as an objective one.

It is well known that offset errors in the multipliers of neural LSIs can have fatal effects on performance. The aim of this study is to understand theoretically how offset errors affect performance of neural LSIs. We have used a single-layer perceptron as an example, and compare our theoretically derived results with computer simulations. We have found that offset errors in the multipliers for the forward process can be canceled out through learning, but those for the updating process cannot be. We have examined the asymptotic behavior of learning for the updating process and derived a mathematical expression for dL, the excess of the averaged loss function L. The derived expression gives us a basis for estimating robustness with respect to the offset errors. Our analysis indicates that dL can be expressed in the form of a quadratic form of offset errors and the inverse of the Hessian matrix of L. We have found that increasing the number of synapses degrades the performacne. We have also learned that enlarging the input signal level and reducing the signal level of the desired response can be effective techniques for reducing the effects of offset errors of the updating process.

Efforts have been cumulated to measure tooth mobility, in order to accurately characterize the mechanical features of periodontal tissues. This paper provides a totally new technique for accomplishing the task of measuring tooth displacement in 6 degrees of freedom, using a range finder. Its intraoral equipment comprises two elements, a moving polyhedron and a referential device, both of which are secured to a subject tooth and several other teeth splinted together. The polyhedron has 6 planar surfaces, each oriented in a distinctly different direction, with each plane facing an opposing range finder mounted on the referential part. If the sensor geometry is provided, the position and orientation of the movable part, vis-a-vis the reference, can be determined theoretically from the distances between all the range finders and their opposing surfaces. This computation was mathematically formulated as a non-linear optimization problem, the numerical solution of which can be obtained iteratively. Its error-propagation formula was also provided as a linear approximation.

UNcorrectable Bit Errors (UNBEs) are important in considering the reliability of Redundant Array of Inexpensive Disks (RAID). They, however, have been ignored or have not been studied in detail in existing reliability analysis of RAID. In this paper, we present an analytic model to study the reliability of declustered-parity RAID by considering UNBEs. By using the analytic model, the optimistic and the pessimistic estimates of the probability that data loss occurs due to an UNBE during the data reconstruction after a disk failed (we call this DB data loss) are obtained. Then, the optimistic and the pessimistic estimates of the Mean Time To Data Loss (MTTDL) that take into account both DB data loss and the data loss caused by double independent disk failures (we call this DD data loss) are obtained. Furthermore, how the MTTDL depends on the number of units in a parity stripe, rebuild time of a failed disk and write fraction of data access are studied by numerical analysis.

This paper proposes a novel FEC (forward error correction) scheme for high-speed wireless systems aiming at mobile computing applications. The proposed scheme combines inner nonredundant error correction with outer parallel encoding random FEC for differentially detected QPSK (quadrature phase shift keying) signals. This paper, first, examines error patterns after the differential detection with nonredundant error correction and reveals that particular double symbol errors occur with relatively high probability. To improve the outer FEC performance degradation due to the double symbol errors, the proposed scheme uses I and Q channel serial to parallel conversion in the transmission side and parallel to serial conversion in the receiving side. As a result, it enables to use simple FEC for the outer parallel encoding random FEC without interleaving. Computer simulation results show the proposed scheme employing one bit correction BCH coding obtains a required Eb/No improvement of 1.2 dB at a Pe of 10-5 compared to that with the same memory size interleaving in an AWGN environment. Moreover, in a Rician fading environment where directional beam antennas are assumed to be used to improve the degradation due to severe multipath signals, an overall Eb/No improvement at Pe of 10-5 of 3.0 dB is achieved compared to simple differential detection when the condition of delay spread of 5 nsec, carrier to multipath signal power ratio of 20 dB and Doppler frequency at 20 GHz band of 150 Hz.

A multicast (point-to-multipoint) protocol of a satellite broadcast channel by a source and many destinations is presented and its performance characteristics are analyzed. We propose a new time-domain multicast scheme for packet satellite channels, retransmission via collisions protocol (called RVCP). RVCP is classified to the automatic repeat request (ARQ) of the multi-selective-repeat scheme and does not require individual channels for each receiving station to request for broadcast packets that have been received incorrectly. Our analytical models show that RVCP performs considerably better than the other protocols, particularly in the situation that packet error rate is less than 10-4 or there are a large number of destinations. It is an excellent characteristic of RVCP that the equipment of the source station need not increase in proportion to the number of destinations, too. And since RVCP is a relatively simple protocol, it is easy to be implemented.

This paper investigates the error rate performance of parallel combinatorial spread spectrum (PC/SS) communicaion systems that use coherent and differential multiphase modulation: multiphase parallel combinatorial spread spectrum (MPC/SS) communication systems. The PC/SS systems are multicode SS systems based on orthogonal pseudo-noise (PN) sequences. Data is transmitted by delivering a combination of multiple PN sequences among a set of pre-assigned PN sequences. In the MPC/SS systems, every PN sequence on transmission is modulated by q-ary coherent or differential phase shift keying (PSK). Symbol error rate (SER) and average bit error rate (BER) in coherent and differential MPC/SS systems are investigated. The BER comparison between the MPC/SS systems and simple multicode SS systems with q-ary coherent and differential PSK is also presented. Numerical results show that the MPC/SS systems are superior to the conventional q-ary PSK systems, if they have equal spectral efficiency.

This paper presents an adaptive coding rate trellis-coded octal phase-shift keying system with rates of 1/3, 1/2, 2/3, and 5/6, under the restriction of a constant transmission bit rate, where the ratio between the informaion bits and error-correcting redundant bits varies according to channel conditions. This system has the advantage of using a simple modem configuration. Because it has no need to change modulation type, transmitter/receiver filters, and clock and carrier recovery circuits, and it can use a convenient Read-Only-Memory table encoder. As for code design, the trellis structures and its signal assignments for rates of 1/3, 1/2, and 5/6 are proposed and investigated, and their BER performances are estimated. As a result, when the system requirement is to keep the bit error rate of 10-4, this system can operate at the lower Eb/No value of 1.5dB on the reduction of transmitting information bits.

We present a comparison of correlated failures for multiversion software using community error recovery (CER) and software breeding (SB). In CER, errors are detected and recovered at checkpoints which are inserted in all the versions of the software. SB is analogous to the breeding of plants and animals. In SB, versions consist of loadable modules, and a driver exchanges the modules between versions to detect and eliminate faulty modules. We formulate reliability models to estimate the probability of failure for software using either CER or SB. Our reliability models assume failures in the checkpoints in CER and the driver in SB. We use beta-binomial distribution for modeling correlated failures of versions, because much of the evidence suggests that the assumption that failures in versions occur independently is not always true. Our comparison indicates that multiversion software using SB is more reliable than that using CER when the probability of failure in the checkpoints in CER or the driver in SB is 10-7.

Constantin and Rao have given a method for constructing single asymmetric error correcting (SAEC) codes based on the theory of the Abelian group, This paper uses the method of generating function in combinatorics to solve the implementation problems of the SAEC group theoretic codes. The encoding and decoding algorithms of the coding scheme perform simple arithmetic operations recursively. The idea of generating function can also be applied to t symmetric errors and simultaneously detect all unidirectional errors (t-syEC/AUED) codes for 1t3.

This paper focuses on recovering from processor transient faults in pipelined multiprocessor systems. A pipelined machine may employ out of order execution and branch prediction techniques to increase performance, thus a precise computation state would not be available. We propose an efficient scheme to maintain the precise computation state in a pipelined machine. The goal of this paper is to implement checkpointing and rollback recovery utilizing the technique of precise interrupt in a pipelined system. Detailed analysis is included to demonstrate the effectiveness of this method.

Calculation Nv(x) of complex order v numerically, we must calculate Df{JN+ε(x)}. When Df{JN+ε(x)} is calculated by the recurrence method, this letter will analyze the error of Df{JN+ε(x)}, and will determine the optimum number of recurrences.

In this paper, the error performance of block coded 8-PSK modulation systems of length 32, designed for unequal error protection (UEP) of messages transmitted over a Rayleigh fading channel, is investigated. Computer simulation are reported showing that, with transmission over a Rayleigh fading channel, a good improvement in coding gain is obtained by the use of a binary linear UEP (LUEP) code as a constituent code in the multilevel construction, compared with conventional block coded modulation (BCM) of the same length.

A modified error correction/detection scheme based on the scheme by Yi and Lee is proposed. Algebraic decoding is used to perform error correction. Error detection is performed by an absolute value test. It is shown that the proposed scheme bridges the performance gap between Yi and Lee's scheme and Forney's optimal scheme.