The normalized least mean square (NLMS) algorithm has the drawback that the convergence speed of adaptive filter coefficients decreases when the reference signal has high auto-correlation. A technique to improve the convergence speed is to apply the decorrelated reference signal to the calculation of the gradient defined in the NLMS algorithm. So far, only the effect of the improvement is experimentally examined. The convergence property of the adaptive algorithm to which the technique is applied is not analized yet enough. This paper first defines a cost function properly representing the criterion to estimate the coefficients of adaptive filter. The name given in this paper to the adaptive algorithm exploiting the decorrelated reference signal, 'normalized least mean EE' algorithm, exactly expresses the criterion. This adaptive algorithm estimates the coefficients so as to minimize the product of E and E' that are the differences between the responses of the unknown system and the adaptive filter to the original and the decorrelated reference signals, respectively. By using the cost function, this paper second specifies the convergence condition of the normalized least mean EE' algorithm and finally presents computer simulations, which are calculated using real speech signal, to demonstrate the validity of the convergence condition.

In this letter, the bandwidth adaptation of an adaptive IIR multiline enhancer is explored. In addition to the problem of bias cancellation of the main structure, different aspects of the proposed filter such as noise equivalent bandwidth and optimal bandwidth are considered and compared with the half power bandwidth of the adaptive multiline enhancer. Since the center frequency of the multiple sinusoids of the input signal is estimated with no bias, with the assumption that the center frequency of the incoming signal is accurately adapted, the error surface of the algorithm is calculated analytically as a function of the filter bandwidth. Computer simulations are used to compare optimum and adapted bandwidths.

Mass measurement system for the measurement of mass of substances placed in randomly vibrating circumstances has been developed. Mass measurement range was defined from 0 g to 400 g for the primary model with the measurement error of approximately 3% when randomly directional vibration of 6 m/sec2 acceleration was applied to the system.

In order that speech recognition system may have a high recognition rate in a noisy environment, a wide-band sharp directional microphone system is required at the input for securing a high S/N ratio. The authors have already reported the realization of a wide-band uni-directional microphone system by three-microphone integration method. In this paper, we intend to describe the derivation of a sharp directivity function and the realization of its microphone system. First, setting the shape of the characteristic function to bring a sharp directional pattern and then expanding it into the Fourier series, we derive a new directivity function. Next, on the basis of this directivity function, we will present a sharp directional microphone system with only three non-directional microphones and the subsequent analog signal processing. And also, the directional pattern acquired by the proposed method and the effect of the dispersion in the sensitivity of the constituent microphones on the directivity are discussed in detail.

This paper describes a new method for estimating the direction of arrival (DOA) using a nonlinear microphone array system based on complementary beamforming. Complementary beamforming is based on two types of beamformers designed to obtain complementary directivity patterns with respect to each other. In this system, since the resultant directivity pattern is proportional to the product of these directivity patterns, the proposed method can be used to estimate DOAs of 2(K-1) sound sources with K-element microphone array. First, DOA-estimation experiments are performed using both computer simulation and actual devices in real acoustic environments. The results clarify that DOA estimation for two sound sources can be accomplished by the proposed method with two microphones. Also, by comparing the resolutions of DOA estimation by the proposed method and by the conventional minimum variance method, we can show that the performance of the proposed method is superior to that of the minimum variance method under all reverberant conditions.

In this paper, we discuss power spectrum overlapping of wideband/narrowband signals and wideband/wideband signals for increasing transmission efficiency. Here, in order to eliminate cross signal interference among those signals, we propose a generalized zero-forcing type decorrelating detection. Our numerical results show that, with the decorrelating detector, the overlapped wideband/wideband signal transmission can much improve the transmission efficiency. This implies that, for a given frequency bandwidth, in order to increase the information transmission rate, we should employ two different kinds of direct sequence spread spectrum-based signals with each power spectrum appropriately overlapped, not taking a single carrier-based approach nor an orthogonal multi-carrier approach.

This paper presents a method of statistical system optimization. The method uses a constraint generation, which is a design methodology based on a hierarchical top-down design, to give specifications to sub-circuits of the system. The specifications are generated not only to reduce the costs of sub-circuits but also to take adequate margin to achieve enough yield of the system. In order to create an appropriate amount of margin, a term which expresses a statistical figure based on Mahalanobis' distance is added to the constraint generation problem. The method is applied to a PLL, and it is confirmed that the yield of the lock-up time reaches 100% after the optimization.

The hardware-software codesign of distributed embedded systems is a more challenging task, because each phase of codesign, such as copartitioning, cosynthesis, cosimulation, and coverification must consider the physical restrictions imposed by the distributed characteristics of such systems. Distributed systems often contain several similar parts for which design reuse techniques can be applied. Object-oriented (OO) codesign approach, which allows physical restriction and object design reuse, is adopted in our newly proposed Distributed Embedded System Codesign (DESC) methodology. DESC methodology uses three types of models: Object Modeling Technique (OMT) models for system description and input, Linear Hybrid Automata (LHA) models for internal modeling and verification, and SES/workbench simulation models for performance evaluation. A two-level partitioning algorithm is proposed specifically for distributed systems. Software is synthesized by task scheduling and hardware is synthesized by system-level and object-oriented techniques. Design alternatives for synthesized hardware-software systems are then checked for design feasibility through rapid prototyping using hardware-software emulators. Through a case study on a Vehicle Parking Management System (VPMS), we depict each design phase of the DESC methodology to show benefits of OO codesign and the necessity of a two-level partitioning algorithm.

In this paper, an architecture of multi-threaded processor for embedded systems is proposed and evaluated comparing with other processors for embedded systems. The experimental results show the trade-off of hardware costs and execution times among processors. Taking proposed multi-threaded processor into account as an embedded processor, design space of embedded systems are enlarged and more suitable architecture can be selected under some design constraints.

As noncoherent direct sequence code-division multiple-access (DS-CDMA) mobile satellite communications, two typical transmission schemes are compared; one is a quasi-synchronous differential BPSK (QS-DBPSK) where orthogonal signals are used for reducing the multiple access interference and the other is M-ary orthogonal signaling (MOS) scheme where orthogonal signals are used for exploiting more efficient modulation. The performances are evaluated in additive white Gaussian noise (AWGN) and shadowed Rician fading (SRF) channels and the effects of timing misalignments in the QS-DBPSK system and the amount of Doppler shifts of a SRF channel are investigated. The results show that MOS much outperforms QS-DBPSK in the region of low system loading up to about 50% and a precise chip synchronization is required for QS-DBPSK. In a SRF channel, it is also shown that QS-DBPSK much outperforms MOS in a slow fading channel but MOS has a performance gain against the large Doppler shift.

A secret sharing scheme allows a secret to be shared among a set of participants, P, such that only authorized subsets of P can recover the secret, but any unauthorized subset can not recover the secret. It can be used to protect important secret data, such as cryptographic keys, from being lost or destroyed without accidental or malicious exposure. In this paper, we consider secret sharing schemes based on interpolating polynomials. We show that, by simply increasing the number of shares held by each participant, there is a multiple assignment scheme for any monotone access structure such that cheating can be detected with very high probability by any honest participant even the cheaters form a coalition in order to deceive him.

A simplified analysis is presented for the reverse link maximum capacity trade-offs between each layer, spectrum efficiency and its multi-rate features of TDMA/W-CDMA and N-CDMA/W-CDMA overlaid systems with the perfect power control based on the measurement of signal-to-interference ratio (CIR). In order to suppress the multi-cross interference, the other important techniques used in the analysis are the ideal notch filtering and the signal level clipper for W-CDMA system transmitters and receivers. We firstly propose the concepts of the notch filtering depth and signal level clipping depth in the paper. The numerical results can be adopted as a guideline in designing the overlaid systems in the various cases as well as a means to investigate the flexibility of sharing of the spread spectrum and their feasibility in the future mobile communication system.

In this paper, we propose a generalized frequency assignment algorithm to minimize the intermodulation products caused by nonlinear amplification in satellite transponder. We also analyze the performance of proposed algorithms in terms of C/IM and execution time. Most of the published algorithms are too restrictive to be applied to the frequency planning of many realistic systems that are usually characterized by multi-level and/or multi-bandwidth. In developing the proposed "TDTI algorithm," we utilized and modified basic concepts of Okinaka's DELINS-INSDEL algorithm to extend its applicability from one-level systems to more general systems. We also propose a modified version of TDTI algorithm called "WTDI-SDELINS" to circumvent the problem of relatively long execution time.

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 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.

In this paper, we examine an optimal reliability assignment/redundant allocation problem formulated as a nonlinear mixed integer programming (nMIP) model which should simultaneously determine continuous and discrete decision variables. This problem is more difficult than the redundant allocation problem represented by a nonlinear integer problem (nIP). Recently, several researchers have obtained acceptable and satisfactory results by using genetic algorithms (GAs) to solve optimal reliability assignment/redundant allocation problems. For large-scale problems, however, the GA has to enumerate a vast number of feasible solutions due to the broad continuous search space. To overcome this difficulty, we propose a hybridized GA combined with a neural-network technique (NN-hGA) which is suitable for approximating optimal continuous solutions. Combining a GA with the NN technique makes it easier for the GA to solve an optimal reliability assignment/redundant allocation problem by bounding the broad continuous search space by the NN technique. In addition, the NN-hGA leads to optimal robustness and steadiness and does not affect the various initial conditions of the problems. Numerical experiments and comparisons with previous results demonstrate the efficiency of our proposed method.

This paper presents an efficient approach for a hardware/software partitioning problem: synthesis of an application-specific coprocessor which accelerates an embedded software running on a main processor. Given a set of data flow graphs (DFGs), most of previous hardware/software partitioning approaches have focused on mapping DFGs to hardware or software. Their common weaknesses are that 1) they ignore various implementation alternatives in realizing DFGs as hardware based on the assumption that only a single hardware implementation exists for a DFG, and that 2) they don't consider the effect of merging on hardware area when synthesizing a coprocessor by merging DFGs. To deal with the first issue, we formulate both the mapping of DFGs to hardware or software and the selection of the appropriate hardware implementation for each DFG as a single integer programming problem, and then apply an iterative algorithm based on the Kernighan and Lin's heuristic to solve the problem. To reduce the CPU time, we have devised data structures that quickly calculate costs of hardware implementations. To deal with the second issue, our method links DFGs with dummy nodes to produce a single large DFG, and then synthesizes a target coprocessor by globally scheduling the DFG and allocating its datapath. Experimental results demonstrate that our approach outperforms the previous approach based on genetic algorithm (GA) in both the coprocessor area and the CPU time.

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 presents a method of determining a fitness function in a genetic algorithm for routing the shortest route via several designated points. We can search for the optimum route efficiently by using the proposed fitness function and its validity is verified by applying it to the actual map data.

This paper proposes a new adaptation-mode control (AMC) for a robust adaptive microphone array with an adaptive blocking matrix (RAMA-ABM). The proposed AMC is based on cross correlations of two microphone signals and uses a state machine for controlling the adaptation to avoid target-signal cancellation. Evaluation with sound data obtained in different acoustic environments demonstrates that the noise reduction by the proposed AMC is 3 dB better than that by the AMC based on the SNR estimate. Subjective listening tests show that the quality of the output signal by the proposed AMC is comparable to or even better than those by the conventional AMCs.