We propose a soft decision Viterbi decoding scheme and a self-interference cancellation method applicable to a Parallel Combinatory CDMA (PC-CDMA) system. In this decoding scheme, branch metric is calculated for every bit by weighting the output levels of the PC-CDMA correlators so as to enable an effective soft decision capability to the system. The effectivity of this scheme is then further enhanced by the use of a simple pseudo-random bit interleaving scheme. Moreover, to increase the capacity of the PC-CDMA system, we propose a simple self-interference cancellation method for self-induced cross-correlation arising from the multipath environment. This further enhances the efficacy of the decoding scheme because the false contributions of the self-induced cross-correlation component are removed from the branch metric prior to soft decision Viterbi decoding. Finally, we simulated a possible PC-CDMA system with a user data rate of 1.92Mbps, transmitting it at a chip rate of 3.84Mcps and at 7.68Mcps under a multipath-Rayleigh fading interference environment. For a chip rate of 7.68Mcps, BER after Viterbi decoding is less than 3.2e-7 even without the use of interference cancellation. For a chip rate of 3.84Mcps, BER after Viterbi decoding with interference cancellation is 1.0e-4.

In this paper, we propose a quasi-optimum multiuser detector using co-channel interference cancellation technique in an asynchronous code-division multiple-access communication system, and evaluate its performance by computer simulations. In the proposed detector, maximum likelihood sequence estimation is performed to compare the original received signal with replicas of the signal which are produced from the demodulation data bit sequence of a co-channel interference canceller. In several conditions, the proposed detector is compared with the co-channel interference canceller, and it is shown that the average bit error rate characteristics of the propose detector are improved considerably.

The computers are connected with each other by the network as a result of the progress of technology in the field of the computer and network, and then all of the data to be processed are transferred quickly and at the real-time through the computer network. However the user can use the computer system at any time, the user must go to the location of the computer system to use the computer resources. The necessities for using the computer system occur anywhere and anytime in spite of the location of the computer system. For this requirement the mobile computing environment (MCE) is expected strongly. In this paper we introduce the model of MCE and discuss the need of the user authentication at entering and logging-in the network in MCE only with a user ID. We propose the method of a user ID assignment from which a server ID can be decided by a simple logical operation. Also, we propose a protocol for a user authentication in MCE and discuss the robustness of security against the various attacking on the route.

This study was conducted to assess the relationship between fatigue and pupillary responses. Pupillary responses, ECG and blood pressure were measured for 24 hours every 30 min in 8 subjects. A questionnaire was used to rate subjective feeling of fatigue. Twenty-four hours were divided equally into four 6-hour blocks. Subjective feeling of fatigue increased markedly in the fourth block, and the difference in subjective fatigue between fourth and first blocks was significant. Of nine pupillary responses, the pupil diameter was found to decrease with time. With respect to the function of the autonomic nervous system such as heart rate, systolic blood pressure and diastolic blood pressure, only heart rate was found to be sensitive to the increased subjective feeling of fatigue. A significant difference was found in the mean pupil diameter and mean heart rate between the last and first blocks. This result indicates that pupil diameter is related to fatigue and can be used to assess fatigue. Possible implications for fatigue assessment are discussed.

In this study, we show how changing a frequency in one of N chaotic circuits coupled by a resistor effects our system by means of both circuit experiment and computer calculation. In these N chaotic circuits, N-1 circuits are completely identical, and the remaining one has altered the value of the oscillation frequency. It is found that for the case of N = 3 when a value of a coupling resistor is gradually increased, only one circuit with different frequency exhibits bifurcation phenomena including inverse period-doubling bifurcation, and for larger value of coupling resistor, the chaotic circuit with different frequency suddenly stops oscillating and the remaining two chaotic circuits exhibit completely anti-phase synchronization.

In client-server database management systems (DBMSs), inter-transaction caching is an effective technique for improving the performance. However, inter-transaction caching requires a cache consistency maintenance (CCM) protocol to ensure that cached copies at clients are kept mutually consistent. Such a protocol could be complex to implement and expensive to run, since several rounds of message exchange may be required. In this paper, we propose a new CCM scheme based on the primary-copy locking algorithm. In the proposed scheme, a number of lock requests and a data-shipping request are combined into a single message packet to reduce client-server interactions, which are known to be very critical to the performance of clientserver DBMSs. We examine its performance tradeoffs on the basis of a simulation model under a wide range of workloads. The performance results indicate that the proposed scheme improves the overall system throughput significantly over the caching two-phase locking and the optimistic two-phase locking scheme. Its higher performance mainly results from its lower communication overhead and lower degree of transaction blocking ratio.

In this paper, we propose a modified R-ISMA (reserved idle signal multiple access) protocol for a wireless local area network (WLAN) with a hybrid system construction. The protocol can support a basic service area as large as that supported by a centralized system and allows the direct transmission between neighbor stations as in a distributed system without the problem of hidden terminals. Since a polling scheme is used during transmission of information packets, an ARQ (auto repeat request) scheme is easily applied. A dynamic analysis using transient fluid approximation analysys is used for performance evaluation. In the analysis, we use Fritchman channel model to describe a burst error environment. Some numerical examples using a set of practical system parameters are given. It is shown that the system performance is improved compared with a centralized system with R-ISMA.

This paper presents the evaluation for personal communication systems (PCS). Two types of PCS are supposed for low and high degree of mobility. The service area with 30km radius is covered by a multiple hexagonal cells, which are micro cells and macro cells for the low mobility and high mobility planes respectively. As for a traffic distribution, uniform and exponentially tapered traffic distributions are assumed. After defining the system model, cost evaluation form along with capacity has been derived. The evaluation and discussions are made in terms of cost economy, capacity and spectrum usage in various conditions. It is shown that there exist the optimum cell radius for the prescribed subscriber numbers and the integration of two systems is desirable for the support of full mobility with cost-effectiveness and spectrum efficiency.

In this article, a new type of diffusion template and an analogic CNN algorithm using this diffusion template for detecting some lung cancer symptoms in X-ray films are proposed. The performance of the diffusion template is investigated and our CNN algorithm is verified to detect some key lung cancer symptoms, successfully.

In this paper a novel narrow-band bandpass filter with an output pair of analytic signals is presented. Since it is based on the complex analog filter, both synthesis and response characteristics of this filter are different from conventional bandpass filters. In the design of this filter, the frequency shift method is employed and the conventional lowpass to bandpass frequency transformation is not required. The analysis and examples show that the output signal pair of the proposed filter possesses same filtering characteristics and a 90 degree phase shifting characteristics in the passband. Therefore, the proposed filter will be used for a single sideband (SSB) signal generator without quadrature generator.

Spectral transform methods have been widely studied for classification and analysis of logic functions. Spectral methods have also been used for logic synthesis, and by use of BDDs, practical-sized synthesis problems have been solved. Wavelet theory has recently attracted the attention of researchers in the signal processing field. The Haar function is used in both spectral methods and in signal processing to obtain spectral coefficients of logic functions of signals. In this paper spectral transform-based analysis of neural nets verifying signal processing and discrete function is presented. A neural net element is defined as a discrete function with multi-valued input signals and multi-valued or binary outputs. The multi-valued variable is realized as a variable (V, W) formed by a pair of a binary value and a multi-value pulse width. The multi-valued encoding is used with the multi-valued Haar function to give meanings to the wavelet coefficients from the view of Boolean algebra. A design example shows that these conceptually different concepts are closely related.

A modified fully-digital code tracking loop is proposed in this paper for direct-sequence spread-spectrum signaling on a frequency-selective fading channel. A data-modulated channel estimator is used to cope with the time-varying Rayleigh fading effect and the data modulation effect, and extract the desired error signal from each path independently in the multipath environments. By taking advantage of the inherent diversity with the maximal ratio combining (MRC) or a proposed Even/odd maximal ratio combining (EMRC) technique, this modified code tracking loop can avoid the problem due to the drift or flutter effects of the error characteristics, and provide better performance on frequency selective fading channels. Extensive computer simulation has verified the analysis and indicated very attractive behavior of the proposed digital tracking loop.

A suggestion for creating an excitable/oscillatory field with solid-state material is proposed. In essence, the idea is to make a spatial array of "mesoscopic particles" with the characteristics of a first-order phase transition. A theoretical computation shows that an auto-wave, or excitable wave, is generated in such an excitable field. A simple example of using this system as a diode in information flow is given.

A new method is proposed for estimating a single complex sinusoid and its parameters (frequency and amplitude) from measurements corrupted by white noise. This method is called the ECKF-SVD method, which is derived by applying an extended complex Kalman filter (ECKF) to a nonlinear stochastic system whose state variables consist of the AR coefficient (a function of frequency) and a sample of the original signal. Proof of the stability is given in the case of a single sinusoid. Simulations demonstrate that the proposed ECKF-SVD method is effective for estimating a single complex sinusoid and its frequency under a low signal-to-noise ratio (SNR). In addition, the amplitude estimation by means of the ECKF-SVD method is also discussed.

The paper provides the algorithm to estimate the deviation bound admitting to recovering irregularly sampled signals in wavelet subspaces, which does not need the symmetricity sampling constraint of Paley-Wiener's and relaxes the deviation bounds in some wavelet subspaces. Meanwhile the method does not need the continuity and decay constraints imposed on scaling functions by Liu-Walter and Chen-Itoh-Shiki.

The TLS method is an unbiased estimator for solving the overdetermined set of linear equations when errors occur in all data. However it doesn't show robustness while the errors have a heavy tailed pdf. In this letter we derive a robust method of TLS (ROTLS) based on the characteristics of TLS solution, where the performance of ROTLS is verified by applying it to the system identification problem.

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.

In this paper, we propose a method to construct structure models of articulated objects from multiple local observations of their motion using state transition analysis of local geometric constraints. The object model is constructed by a bottom-up approach with three levels. Each level groups sensor data with a constraint among local features observed by the sensor, and constructs the local model. If the sensor data in current model conflict, the model is reconstructed. In each level, the first level estimates a local geometric feature from the local sensor data (eg. edge, feature point) The second level estimates a rigid body from the local geometric feature. The third level estimates an object from the rigid bodies. In the third level, the constraint between rigid bodies is estimated by transition states, which are motions between rigid bodies. This approach is implemented on a blackboard system.

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.

Electric fishes generate an AC electric field around themselves by the electric organ in the tail. Spatial distortion of the field by nearby objects is detected by an electroreceptor array located an over the body surface to localize the object electrically when other senses such as vision and mechanosense are useless. Each fish has its own 'frequency band' for its electric organ discharges, and jamming of the electrolocation system occurs when two fish with similar discharge frequencies encounter. To avoid janmming, the fish shift their discharge frequencies in appropriate directions. A computational algorithm for this electrical behavior and its neuronal implementation by the brain have been discovered. The design features of the system, however, are rather complex for this simple behavior and cannot be readily explained by functional optimization processes during evolution. To gain insights into the origin of the design features, two independently evolved electric fish species which perform the same behavior are compared. Complex features of the neuronal computation may be explained by the evolutionary history of neuronal elements.