The paper proposes a transmitter diversity scheme with a desired signal selection for the mobile communication systems in which the severe cochannel interference (CCI) is assumed to occur at the base station. The feature of the proposed scheme is that the criterion of the downlink branch selection is based on the desired signal power estimated by the correlation between the received signal and the unique word at the matched filter. Moreover, the unique word length control method according to the instantaneous SIR is applied to the proposed scheme, taking account of the uplink transmission efficiency. Computer simulation results show that the proposed scheme provides the better performance than the conventional transmitter diversity in the severe CCI environments, and that the unique word length control method applied to the proposed scheme decreases the unique word length without the degradation of the transmission quality, comparing with the fixed unique word length method.

A novel Multi-Level Partitioning (MLP) technique taking into account real-world constraints for hardware-software partitioning in Distributed Embedded Multiprocessor Systems (DEMS) is proposed. This MLP algorithm uses a gradient metric based on hardware-software cost and performance as the core metric for selection of optimal partitions and consists of three nested levels. The innermost level is a simple binary search that allows quick evaluations of a large number of possible partitions. The middle level iterates over different possible allocations of processors (that execute software) to subsystems. The outermost level iterates over the number of processors and the hardware cost range. Heuristics are applied to each level to avoid the expensive exhaustive search. The application of MLP as a recently purposed Distributed Embedded System Codesign (DESC) methodology shows its feasibility. Comparisons between real-world examples partitioned using MLP and using other existing techniques demonstrate contrasting strengths of MLP. Sharing, clustering, and hierarchical system model are some important features of MLP, which contribute towards producing more optimal partition results.

This paper briefly surveys architectural technologies of recent or future high-performance, low-power processors for improving the performance and power/energy consumption simultaneously. Achieving both high performance and low power at the same time imposes a lot of challenges on processor design, and therefore gives us a lot of opportunities for devising new technologies. The paper also tries to provide some insights into the technology direction in future.

This paper presents efficient time slot assignment algorithms applicable to the uplink of SDMA system. A frame consists of one control time slot and multiple communication time slots where terminals in different angular positions share the same time slot. In the proposed algorithms, a time slot is assigned to a new terminal considering not only the signal quality of the new terminal but also the signal quality of active terminals. Simple calculation method for estimated signal-to-interference plus noise ratio (SINR) is employed to decrease the computational complexity. The performance of the proposed algorithms is evaluated by computer simulation and compared with sectorized systems to show the validity of the proposed algorithms.

This paper is, in half part, written in review nature, and presents recent theoretical results on linear-filtering and -prediction problems of nonstationary Gaussian processes. First, the basic concepts, signal and noise, are mathematically characterized, and information sources are defined by linear stochastic differential equations. Then, it is shown that the solution to a conventional problem of filtering or prediction of a nonstationary time series is, in principle, reducible to a problem, of which solution is given by Kalman-Bucy's theory, if one can solve a problem of finding the canonical representation of a Gaussian process such that it has the same covariance functions as those of the time series under consideration. However, the problem mentioned above is left open. Further, the problem of time-frequency analysis is discussed, and physical realizability of the evolutionary, i.e., the online, spectral analyzer is shown. Methods for dealing with differential operators are presented and their basic properties are clarified. Finally, some of related open problems are proposed.

For physically disabled persons, the conventional computer keyboard is insufficient as a useable communication device. In this paper, Morse code is selected as a communication adaptive device for persons with impaired hand coordination and dexterity. Morse code is composed of a series of dots, dashes, and space intervals. Each element is transmitted by sending a signal for a defined length of time. Maintaining a stable typing rate by the disabled is difficult. To solve this problem, a suitable adaptive automatic recognition method, which combines a variable degree variable step size LMS algorithm with a learning vector quantization method, was applied to this problem in the present study. The method presented here is divided into five stages: space recognition, tone recognition, learning process, adaptive processing, and character recognition. Statistical analyses demonstrated that the proposed method elicited a better recognition rate in comparison to alternative methods in the literature.

The capability of frequency-swept cross-borehole radar to detect an empty rectangular cylinder embedded in a dielectric medium is simulated numerically by employing the boundary element method. The frequency loci providing the strongest double dips in the received signal pattern are plotted as functions of the observation distance and the cross-sectional width. It is found that, regardless of the shape of the rectangular cross-section, the strongest double dips become double nulls in the near-field region.

This paper describes an efficient k-out-of-n threshold digital signature scheme for a smart card based system where a signer uses multiple cards so that the signature can be issued in a dependable manner. The main feature of our method is that it does not require a secret communication path among these cards in the signature issuing protocol, and that it requires low communication and computational complexity. Former is an advantage under the current export control regulation which makes hard to export more than 56-bit cipher techniques, and latter is advantage over so-called robust signature.

An aspect of the diverse developments of digital signal processing (DSP) over the last decade are summarized. The current progress of some core fields from the widespread fields are treated in this paper. The selected fields are filter design, wavelet theory and filter bank, adaptive signal processing, nonlinear filters, multidimensional signal processing, intelligent signal processing, and digital signal processor. Through the overview of recent research activities, the interdisciplinary character of the DSP should be proved. Some challenging research direction is described in the last section.

ID-based key sharing scheme is one of the important topics in Key management, and the Key Predistiribution System (KPS) is one of the major divisions of such key sharing schemes. In KPS, in order to share a common key between the participants, one of the participants need to simply feed-in his partner's identifier value into their secret-algorithm. In contrast to its such remarkable property and its high contribution to the field of key management for digital signature, it has downsides as well. In this paper, we propose an efficient signature scheme on the KPS infrastructure that can overcome such difficulties that are faced. It is shown that if an ID-based key sharing system belonging to KPS is provided, the new digital signature scheme can be used straightforwardly. Moreover, this signature scheme is proven to be secure if the discrete logarithm is reasonably complex. There already exists other digital signature scheme which are also based on KPS, but they contain inevitable flaws: its verifier is restricted and a tamper resistant module(TRM) is required. Our method resolved these problems. In our signature scheme, it is an ensured fact that, all signatures are authenticated by any entity, which is based on the inherence behavior of key generator and not of some common key. Moreover, TRM is not required in our scheme. In order to describe our new scheme, a new concept of "one-way homomorphism" is introduced.

A new approach to 3-D profilometry for the white light interferometric (WLI) is presented. The proposed method is the extended depth from focus (EDFF) that determine the zero optical path difference (OPD) from the quantity of fringe contrast degradation of white light interferometer. In the method, the variance of the mismatch function and the modified local variance function are used as the focus measures. The method has a theoretically unlimited range and can profile with subpixel accuracy both optically rough and smooth surfaces without changing algorithm.

This paper, for the first time, presents a provably secure signature scheme with message recovery based on the elliptic-curve discrete logarithm. The proposed scheme is proven to be secure in the strongest sense (i.e., existentially unforgeable against adaptively chosen message attacks) in the random oracle model under the discrete logarithm assumption. We give a concrete analysis of the security reduction. When practical hash functions are used in place of truly random functions, the proposed scheme is almost as efficient as the elliptic-curve version of the Schnorr signature scheme and existing schemes with message recovery such as the elliptic-curve version of the Nyberg-Rueppel and Miyaji schemes.

In this paper, we investigate the blocking characteristics of all-optical WDM (Wavelength-Division Multiplexing) networks under distributed wavelength assignment policies. For assigning wavelengths in a distributed manner, we consider two algorithms: random and locally-most-used algorithm. For a random wavelength assignment policy, we develop new blocking models of unidirectional/bidirectional ring networks based on the M/M/c/c queueing models under uniform/nonuniform traffic conditions. These models are shown to be more accurate than the previous blocking models since our approach considers the large traffic correlation among links in ring networks. We also analyze the blocking performance of the locally-most-used algorithm by comparing with that of the globally-most-used algorithm in fixed routing networks. We show that our analysis models match well with the simulation results in ring and mesh networks. Through the comparison with the previous centralized/distributed algorithms, it is demonstrated that the distributed locally-most-used algorithm is computationally efficient with good blocking performance.

The signed regressor algorithm, a variation of the least mean square (LMS) algorithm, is characterized by the estimation way of using the clipped reference signals, namely, its sign (). This clipping, equivalent to quantizing the reference signal to 1, only increases the estimation error by about 2 dB. This paper proposes to increase the number of the quantization steps to three, namely, 1 and 0, and shows that the 'tri-quantized-x' normalized least mean square (NLMS) algorithm with three quantization steps improves the convergence property.

An automated method for cryptanalysis of DFT-based analog speech scramblers is presented through statistical estimation treatments. In the proposed system, the ciphertext only attack is formulated as a combinatorial optimization problem leading to a search for the most likely key estimate. For greater efficiency, we also explore the benefits of genetic algorithm to develop an estimation method which takes into account the doubly stochastic characteristics of the underlying keyspace. Simulation results indicate that the global explorative properties of genetic algorithms make them very effective at estimating the most likely permutation and by using this estimate significant amount of the intelligibility can be recovered from the ciphertext following the attack on DFT-based speech scramblers.

Methods for implementing SS7 functions are proposed for a large-capacity decentralized switching node; they satisfy the condition of hiding distributed configurations from adjacent nodes. First, line accommodation and acquisition methods are clarified for a large-capacity switching node in which multiple modules are used to realize trunk circuits and SS7 signaling links. Two methods are then proposed for allocating SS7 functions within the switching node. One distributes the functions over multiple circuit-switched modules (distributed allocation) while the other centralizes the functions in dedicated signaling modules (centralized allocation). We quantitatively evaluate both methods in terms of node scale versus the number of modules and signaling links required, the inter-module data transfer rate required, and the node traffic handling capacity when a particular module fails. From the evaluation results, we show that the distributed allocation should be employed for small-scale nodes and the centralized allocation for large-scale nodes. We also show the effectiveness of a method for avoiding a characteristic problem that arises when a particular module fails. Finally, we implement an experimental system as an example.

New designs of MAXFLAT discrete and differentiating Hilbert transformers are presented using their interrelationships with digital differentiators. The new designs have the explicit formulas for their tap-coefficients, which are further modified to obtain a new class of narrow transition band filters, with a performance comparable to the Chebyshev filters.

This letter points out some flaws in the previous works on UKS (unknown key-share) attacks. We show that Blake-Wilson and Menezes' revised STS-MAC (Station-to-Station Message Authentication Code) protocol, which was proposed to prevent UKS attack, is still vulnerable to a new UKS attack. Also, Hirose and Yoshida's key agreement protocol presented at PKC'98 is shown to be insecure against public key substitution UKS attacks. Finally, we discuss countermeasures for such UKS attacks.

In the beginning of the new century, many information appliance (IA) products will replace traditional electronic appliances to help people in smart, efficient, and low-cost ways. These successful products must be capable of communicating multimedia information, which is embedded into the electronic appliances with high integration, innovation, and power-throughput tradeoff. In this paper, we develop a codesign procedure to analyze, compare, and emulate the multimedia communication applications to find the candidate implementations under different criteria. The experimental results demonstrate that in general, memory technology dominates the optimal tradeoff and ALU improvements impact greatly on particular applications. The results also show that the proposed procedure is effective and quite efficient.

In this letter we propose a filter for extracting a quasi-periodic signal from a noisy observation using wavelets. It is assumed that the instantaneous frequency of the signal is known. A particularly difficult task when the frequency and amplitude of the desired signal are varying with time is shown. The proposed algorithm is compared with three other methods.