This paper addresses the problem of designing an unconditionally secure conference system that fulfills the requirements of both traceability and dynamic sender. In a so-called conference system, a common key is shared among all authorized users, and messages are encrypted using the shared key. It is known that a straightforward implementation of such a system may present a number of security weaknesses. Our particular concern lies in the possibility that unauthorized users may be able to acquire the shared key by illegal means, say from one or more authorized but dishonest users (called traitors). An unauthorized user who has successfully obtained the shared key can now decrypt scrambled messages without leaving any evidence on who the traitors were. To solve this problem, in this paper we propose a conference system that admits dynamic sender traceability. The new solution can detect traitors, even if the sender of a message is dynamically determined after a shared key is distributed to authorized users. We also prove that this scheme is unconditionally secure.

In this work, using 0.2 µm GaAs modulation doped FET (MODFET), a high performance downconverter MMIC was developed for direct broadcasting satellite (DBS) applications. The downconverter MMIC showed a noise figure of 4.3 dB which is lower by 5 dB than conventional ones, and required only a low LO power of -10 dBm for normal DBS operation. At a low LO power of -10 dBm, the power consumption was 175 mW, which is lower than 50 percent of conventional ones. The frequency response of conversion gain exhibited a low gain ripple of 0.9 dB, and the LO leakage power was suppressed to a lower value than -30 dBm under a LO input power of -10 dBm. The fabricated chip exhibited a small size of 0.840.9 mm2. The objectives of this work are to improve the traditional direct broadcasting satellite (DBS) downconverters by an efficient circuit design and to describe the techniques employed in the design.

An adaptive rate communication system based on the N-MSK modulation technique is described. Two examples of the system using a 2-MSK adaptive modulation scheme and a 4-MSK adaptive modulation scheme are presented and analysed in slow fading channel. The channel attenuation obeys either Rayleigh or lognormal distribution. The proposed adaptive rate communication system is able to track slow variations of channel attenuation and the average system throughput is therefore increased at a given BER.

In this paper, two efficient codebook searching algorithms for vector quantization (VQ) are presented. The first fast search algorithm utilizes the compactness property of signal energy of orthogonal transformation. On the transformed domain, the algorithm uses geometrical relations between the input vector and codeword to discard many unlikely codewords. The second algorithm, which transforms principal components only, is proposed to alleviate some calculation overhead and the amount of storage. The relation between the principal components and the input vector is utilized in the second algorithm. Since both of the proposed algorithms reject those codewords that are impossible to be the nearest codeword, they produce the same output as conventional full search algorithm. Simulation results confirm the effectiveness of the proposed algorithms.

We propose an encoding method for one-point algebraic geometry codes that usually requires less computation than the ordinary systematic encoder.

We study a class of nonlinear dynamical systems to develop efficient algorithms. As an efficient algorithm, interior point method based on Newton's method is well-known for solving convex programming problems which include linear, quadratic, semidefinite and lp-programming problems. On the other hand, the geodesic of information geometry is represented by a continuous Newton's method for minimizing a convex function called divergence. Thus, we discuss a relation between information geometry and convex programming in a related family of continuous Newton's method. In particular, we consider the α-projection problem from a given data onto an information geometric submanifold spanned with power-functions. In general, an information geometric structure can be induced from a standard convex programming problem. In contrast, the correspondence from information geometry to convex programming is slightly complicated. We first present there exists a same structure between the α-projection and semidefinite programming problems. The structure is based on the linearities or autoparallelisms in the function space and the space of matrices, respectively. However, the α-projection problem is not a form of convex programming. Thus, we reformulate it to a lp-programming and the related ones. For the reformulated problems, we derive self-concordant barrier functions according to the values of α. The existence of a polynomial time algorithm is theoretically confirmed for the problem. Furthermore, we present the coincidence with the gradient vectors for the divergence and a modified barrier function. These results connect a part of nonlinear and algorithm theories by the discreteness of variables.

In this paper, we deal with the problem of compatibility class encoding, and propose a novel algorithm for finding a good functional decomposition with application to LUT-based FPGA synthesis. Based on exploration of the design space, we concentrate on extracting a set of components, which can be merged into the minimum number of multiple-output CLBs or LUTs, such that the decomposition constructed from these components is also minimal. In particular, to explore more degrees of freedom, we introduce pliable encoding to take over the conventional rigid encoding when it fails to find a satisfactory decomposition by rigid encoding. Experimental results on a large set of MCNC91 logic synthesis benchmarks show that our method is quite promising.

This paper describes a unique motion estimation and compensation (ME/MC) hardware architecture for a scene-adaptive algorithm. By statistically analyzing the characteristics of the scene being encoded and controlling the encoding parameters according to the scene, the quality of the decoded image can be enhanced. The most significant feature of the architecture is that the two modules for ME/MC can work independently. Since a time interval can be inserted between the operations of the two modules, a scene-adaptive algorithm can be implemented in the architecture. The ME/MC architecture is loaded on a single-chip MPEG-2 video encoder.

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.

Using decision trees to fill the missing values in data has been shown experimentally to be useful in some domains. However, this is not the general case. In other domains, using decision trees for imputing missing attribute values does not outperform other methods. Trying to identify the reasons behind the success or failure of the various methods for filling missing values on different domains can be useful for deciding the technique to be used when learning concepts from a new domain with missing values. This paper presents a technique by which to approach to previous goal and presents the results of applying the technique on predicting the success or failure of a method that uses decision trees to fill the missing values in an ordered manner. Results are encouraging because the obtained decision tree is simple and it can even provide hints for further improvement on the use of decision trees to impute missing attribute values.

This paper describes an embedded software scheme for a single-chip MPEG-2 encoder that executes concurrent video, audio, and system encoding in real-time. The software features a scalable module structure, which is hierarchically composed and has expandable plug-in modules. For increased applicability, several task-modules are prepared for the respective video, audio, and system processing. In addition, an effective task management scheme that features polling and interrupt-based task switching has been proposed in order to achieve real-time operation. The software having these features and including all task-modules is implemented on a single media-processor D30V on a single chip MPEG-2 video, audio, and system encoder. This encoder realizes real-time MPEG-2 video encoding, Dolby Digital or MPEG-1 audio encoding, and system encoding that generates TS or PS over 50 Mbps for various applications. Assuming a DVD or DTV encoder system, the software is reconstructed with less than 56.6-kbytes of instruction and 145.6 MIPS performance. The single media-processor with 64-kbytes of instruction RAM and 162 MIPS performance, running at a clock rate of 162 MHz, can successfully accomplish a real-time operation with the proposed embedded software.

In this paper, a new expression is derived for the bit error rate (BER) performance of Gray-encoded MDPSK for M=2 and 4 in orthogonal frequency division multiplexing (OFDM) systems over time-variant and frequency-selective Rayleigh fading channels. We assume that the guard time is sufficiently larger than the delay spread to solve the intersymbol interference (ISI) problem on the demodulated OFDM signal. In this case, the performance depends on the Doppler spread of fading channel. The closed form expression for the bit error probability of MDPSK/OFDM extended from the result in [5] shows that the BER performance of MDPSK is determined by (N + NG ) fD Ts where N is the number of subchannels, NG the length of the guard interval, fD the maximum Doppler frequency, and Ts the sampling period. The theoretical analysis results are confirmed by computer simulations for DPSK and QDPSK signals.

A single-chip MPEG-2 video, audio, and system encoder LSI has been developed. It performs concurrent real-time processing of MPEG-2 422P@ML video encoding, 2-channel Dolby Digital or MPEG-1 audio encoding, and system encoding that generates a multiplexed transport stream (TS) or a program stream (PS). Advanced hybrid architecture, which combines a high performance VLIW media-processor D30V and hardwired video processing circuits, has been adopted to satisfy the demands of both high flexibility and enormous computational capability. A unified control scheme has been newly proposed that hierarchically manages adaptive task priority control over asynchronous video, audio, and system encoding processes in order to achieve real-time concurrent processing using a single D30V. Dual dedicated motion estimation cores consisting of a coarse ME core (CME) for wide range searches and a fine ME core (FME) for precise searches have been integrated to produce high picture quality while using a small amount of hardware. Adopting these features, a single-chip encoder has been fabricated using 0.25-micron 4-layer metal CMOS technology, and integrated into a 14.2 mm 14.2 mm die with 11 million transistors.

Increasing the capacity and intelligence of the next-generation Internet requires the application of optical technologies to switching nodes as well as transmission lines, and the development of advanced network architectures with end-to-end connection setup processing at the source node and autonomous routing at intermediate nodes. In the present paper, we design a new CDM-based switching scheme and node configurations that are suitable for a photonic IP switching system, in which a set of multiple-encoding CDM codes is utilized as routing information. In addition, we calculate the BER characteristics of the multiple-encoding CDM system by simulation. Under the condition that the chip duration of a certain code is a multiple of that of another code, the BER characteristics of the multiple-encoding system are shown to coincide with that of the single-encoding system by the longer code.

The encoding procedure that allows one to represent integers by binary vectors (codewords) in such a way that addition is replaced with the OR operation applied to these vectors is described. The codeword of the sum is constructed using the decoding algorithm. As a result, many of the transformations can be realized using parallel processing, and the method can be considered as a competitor to existing computer arithmetic.

An MPEG-2 422P@HL encoder chip set composed of a preprocessing LSI, an encoding LSI, and a motion estimation LSI is described. This chip set realizes a two-type scalability of picture resolution and quality, and executes a hierarchical coding control in the overall encoder system. Due to its scalable architecture, the chip set realizes a 422P@HL video encoder with multi-chip configuration. This single encoding LSI achieves 422P@ML video, audio, and system encoding in real time. It employs an advanced hybrid architecture with a 162 MHz media processor and dedicated video processing hardware. It also has dual communication ports for parallel processing with multi-chip configuration. Transferring of reconstructed data and macroblock characteristic data between neighboring encoder modules is executed via these ports. The preprocessing LSI is fabricated using 0.25 micron three-layer metal CMOS technology and integrates 560 K gates in an area of 12.0 mm 12.0 mm . The encoding LSI is fabricated using 0.25 micron four-layer metal CMOS technology and integrates 11 million transistors in an area of 14.2 mm 14.2 mm . The motion estimation LSI is fabricated using 0.35 micron three-layer metal CMOS technology. It integrates 1.9 million transistors in an area of 8.5 mm 8.5 mm . This chip set makes various system configurations possible and allows for a compact and cost-effective video encoder with high picture quality.

A software requirements specification (SRS) is a document at the first phase of software development. Since it is difficult to make an accurate SRS at the beginning of software development, we propose a supporting method to detect and interpret the inconsistency of SRS. First, we classify and define the inconsistency of SRS. Next, we describe how to detect and interpret the inconsistency of SRS. We use the Requirements Frame Model to detect the inconsistency of SRS. We apply the Dempster and Shafer's theory to interpret the inconsistency of SRS. We illustrate our method with an example.

This paper summarizes power reduction methods applicable for VLSI bus systems in terms of reduction of signal swing, effective capacitance reduction and reduction of signal transition, which have been studied in authors' research group. In each method the basic concept is reviewed quickly along with some examples of its application. A future perspective is also described in conclusion.

We propose a query processing method for amalgamated knowledge bases. Our query processing method is an extension of the magic sets technique for query processing in amalgamated knowledge bases, augmented with the capabilities of handling amalgamated atoms. Through rewriting rules in a given amalgamated knowledge base, our method offers the advantages associated with top-down as well as bottom-up evaluation. We discuss how to handle amalgamated atoms, consider how to check whether an amalgamated atom is satisfiable in a fact set and how to extend a fact set by inserting an amalgamated atom. We also give the transformation procedures for amalgamated knowledge databases and show the correctness of our method.

In microwave hyperthermia for cancer therapy, two power feeding techniques can be utilized: incoherent and coherent operations. In the incoherent operation, not-synchronized microwave power is fed into each array element, whereas the coherent operation is achieved by feeding synchronized microwave to the array elements. The authors have been studying the coaxial-slot antenna for interstitial microwave hyperthermia. The antenna is usually employed as an array applicator inserting several antennas into the tissue to generate large heating area. So far we have examined the control of the heating pattern by feeding techniques in order to obtain more uniform and enlarged heating region. Particularly, `tip-heating,' which means sufficient heating at the area near the tip of the applicator, is significant not to damage surrounding normal tissue in interstitial hyperthermia. In this paper, two feeding techniques are combined and calculated temperature distributions in a hexagonal array applicator are examined by solving Pennes bioheat transfer equation by finite difference method. As a result, in the coherent feeding, large heating area was obtained, while better tip-heating was achieved in the incoherent feeding. Moreover, an instance of sequential combination of two feeding techniques is depicted. In this case, temperature distribution had both characteristics of large heating area and tip-heating, therefore the ability of the control of heating characteristics by sequential combination of the coherent and the incoherent feedings was presented.