Recently, there has been increasing interest in Code Division Multiplex (CDM) systems. We reported the CDM system using the -chip shift multiplex operation. So far the performance of this system evaluated under the optimum . In this letter, we evaluate an influence of the phase difference between the groups on BER performance in 2M-plex system.

The performance of processing elements can be improved by the progress of VLSI circuit technology, while the communication overhead can not be negligible in parallel processing system. This paper presents a unified scheduling that allocates tasks having different task processing times in multiple processing elements. The objective function is formulated to measure communication time between processing elements. By employing constraint conditions, the scheduling efficiently generates an optimal solution using an integer programming so that minimum communication time can be achieved. We also propose a VLSI processor for robotics whose latency is very small. In the VLSI processor, the data transfer between two processing elements can be done very quickly, so that the communication cycle time is greatly reduced.

The paper considers multiple-valued logic systems having the property that the ambiguity of the system increases as the ambiguity of each component increases. The partial-ordering relation with respect to ambiguity with the greatest element 1/2 and minimal elements 0, 1 or simply the ambiguity relation is introduced in the set of truth values V {0, 1/ (p1), , 1/2, , (p2) / (p1), 1}. A-monotonic p-valued logic functions are defined as p-valued logic functions monotonic with respect to the ambiguity relation. A necessary and sufficient condition for A-monotonic p-valued logic functions is presented along with the proofs, and their logic formulae using unary operators defined in the ambiguity relation are given. Some discussions on the extension of theories to other partial-ordering relations are also given.

The path diversity improvement inherent in direct sequence spread spectrum (DS/SS) signalling under multi-path propagation environments is investigated for mobile/personal radio communications systems that employ DPSK modulation. The bit error rate (BER) performance of post-demodulation selection diversity reception is theoretically analyzed in the presence of noise-only-paths in the time window for diversity combining. Results of laboratory experiments conducted to evaluate the BER performance are also presented. It is shown that the experimental results agree well with the theoretical BER.

Formal verification has become an increasing prominent technique towards establishing the correctness of hardware designs. We present a framework to specifying and verifying the design of systolic architectures. Our approach allows users to represent systolic arrays in Z specification language and to justify the design semi-automatically using the verifier. Z is a notation based on typed set theory and enriched by a schema calculus. We describe how a systolic array for matrix-vector multiplication can be specified and justified with respect to its algorithm.

We propose a direct-sequence spread-spectrum multi-access (DS/SSMA) receiver that incorporates multipath diversity combining and multistage co-channel interference (CCI) cancellation. This receiver structure which is more resistant to the near/far problem essentially removes more and more of the CCI with each successive cancellation stage. With the assumption that perfect channel estimates have been obtained, we analyze the bit error rate (BER) performance of this system when received powers are unequal. Results show that the BER can approach that of a single-user case as the number of CCI cancellation stages increases.

The inverted slot line (ISL) has been propoaed for millimeter-wave LiNbO3 optical modulator. It is simple in structure, and capable of achieving the perfect velocity matching between carrier and modulating waves. The excellent performance of the ISL optical modulator has been demonstrated at 100 GHz, and the extension into the 50 GHz range is being expected. This paper addresses the analysis of the ISL based on the spectral domain approach. The major results obtained here are the demonstration of the perfect velocity matching not only at 10 GHz but also at 50 GHz, and the characterization of the ISL in terms of effective refractive index, characteristic impedance, overlap integral factor and transmission loss. The depth of optical phase modulation is also estimated at 50 GHz to show a promising performance in the millimeter-wave frequency range. The effective refractive index and the characteristic impedance are found to be theoretically predictable, but the field profile, the overlap integral factor and the transmission loss are not necessarily in good agreement with measurements. As a result of analysis, it can be concluded that the Y-cut substrate is superior to the Z-cut substrate in the following respects: 1. Coupling with the surface wave mode hardly occurs near the operating frequency range. 2. The perfect velocity matching can be attained with a larger spacing between the electrode and the ground plane. 3. The transmission loss is smaller. 4. The field intensity and the voerlap integral factor do not seem to be much deteriorated in the actual ISL.

This paper presents two methods for securely realizing caller-authenticated and callee-specified calls over telecommunication networks with terminals that accept IC cards having KPS-based cryptographic functions. In the proposed protocols, users can verify that the partner is the proper owner of a certain ID or a certain pen name. Users' privacy is protected even if they do the caller-authenticated and callee-specified calls and do not pay their telephone charge in advance.

Let TBP be the server busy period of an M/G/1 queueing system characterized by arrival intensity λ and service time c.d.f. A(τ). In this paper, we investigate the regularity structure of the Laplace transform σBP(s)=E[] on the complex s-plane. It is shown, under certain broad conditions, that finite singular points of σBP(s) are all branch points. Furthermore the branch point s0 having the greatest real part is always purely negative and is of multiplicity two. The basic branch point s0 and the associated complex structure provide a basis for an asymptotic representation of various descriptive distributions of interest. For a natural relaxation time |s0|-1 of the M/G/1 system, some useful bounds are obtained and the asymptotic behavior as traffic intensity approaches one is also discussed. Detailed results of engineering value are provided for two important classes of service time distributions, the completely monotone class and the Erlang class.

There have been few studies on formal approaches to the specification and realization of asynchronous sequential circuits. For synchronous sequential circuits, an algebraic method is proposed as one of such approaches, but it cannot be applied to asynchronous ones directly. This paper describes an algebraic method of specifying the abstract behavior of asynchronous sequential circuits. We select an daisy chain arbiter as an example of them. In the arbiter, state transitions are caused by input changes, and all the modules do not always make state transitions simultaneously. These are main obstacles to specify it in the same way as sychronous sequential circuits. In order to remove them, we modify the meaning of input in specifications and introduce pseudo state transitions so that we can regard all the modules as if they make state transitions simultaneously. This method can be applied to most of the other asynchronous sequential circuits.

This paper describes a computer-aided service creation environment (CSCE) for the intelligent network which supports easier graphical specification description for service designers of various skill levels, and service logic program (SLP) generation. The CSCE design concept consists of stepwise service specification description and SLP generation, message sequence chart description language (LSDL: Layered Service Specification Description Language), computer-aided sophisticated interface (IEDs: Intelligent Editors), automatic specification verification and rapid service prototyping. Service specification is described by three steps and in LSDL or SDL, and SLPs are generated through three converters referring to two knowledge databases. Three tests are conducted on the specifications described. The effectiveness of the CSCE is demonstrated by the results that the amount of SLP descriptions for five new practical services using the CSCE is reduced to less than about 20% in LSDL description, compared to C language description.

This paper describes the performance evaluation of the Translation Look-aside Buffer (TLB) for highly integrated microprocessors, especially concerning the TLB in the SPARC Reference MMU specification. The analysis covers configurations, the number of entries, and replacement algorithms for the instruction TLB and the data TLB, which are assumed to be practically integrated on one die. We also present performance improvement using a Page Table Cache (PTC). We evaluate some types of TLB configurations with software simulation and excute the Systems Performance Evaluation Cooperative (SPEC) programs.

The purpose of this paper is to propose a technique to simplify the communications software descriptions written in a procedural language in order to enhance their comprehensibility. Although such a technique was not much studied and discussed in the past, this technique is important to realize high productivity and high quality of the communications software by reducing the complexity of the software description. This paper firstly systematically presents various simplification methods with their principles for the descriptions of the communications software from the viewpoints of their layout, syntactical structures etc. Then, it describes a simplification support system based on these principles for the software specifications written in SDL. Lastly, this paper demonstrates the usefulness and effectiveness of the proposed simplification technique by analyzing the evaluation results of the simplification system.

In LOTOS, requirements for a distributed system are described as a service definition. On the protocol level, each node (protocol entity) must exchange some data values and synchronization messages to provide a service described in a service definition. The tuple of the specifications of all nodes in the system which provide the service is called as a protocol specification. In order to develop the communication programs satisfying a given service definition, it is very important to develop the correct protocol specification. For this purpose, the simulation of protocol specifications is useful and it is desirable that the designer can observe how a protocol specification is executed in parallel and how synchronization messages are exchanged among the nodes. Therefore, we have developed a new tool named PROSPEX. For a given pair of a service definition and a protocol specification, it executes the protocol specification in parallel and shows its execution process graphically on X Window System. If the protocol specification executes an event sequence which does not satisfy the service definition, then PROSPEX informs it to the designer. In this paper, the design and usefulness of PROSPEX are described.

An integrated platform INTEGRAL has been developed for developing large complex communication software systems. At the heart of INTEGRAL, a pair of graphical and textual specification languages, DISCOL (DIStributed Communication-Oriented Language), has been developed based on Petri nets. Around DISCOL, a wide variety of design and analysis tools have been integrated in coherent manner so that a seamless support from design to verification and testing are made available along with software life-cycle. The platform has been applied to the development of a PBX simulator named UICPBX. In the development, some real communication services have been fully specified with DISCOL. Such experiences have revealed the effectiveness of the proposed techniques.

Net-Oriented Analysis and Design (NOAD) is defined as three items: (1) Various nets are utilized as an effective modeling method. (2) Inter-relationships among verious nets are determined. (3) Verification or analysis methods for nets are provided and they are implemented based on the mathematical theory, that is Net theory. Very few methods have been presented to satisfy these three items. For example, the Real-Time SA method covers item (1) only. The Object-Oriented Analysis and Design method (OOA/OOD) covers items (1) and (2). NOAD can be regarded as an extension to OOA/OOD. This paper discusses how effectively various nets have been used in actual software development support metnods and tools and evaluates such several methods and tools from the NOAD viewpoint.

This paper presents unique specification environments for LOTOS, which is one of FDTs (Formal Description Techniques) developed in ISO. We first discuss the large gap in terms of syntax and semantics between informal specifications at the early stage of specification design and formal specifications based on FDT such as LOTOS. This large gap has been bridged by human intelligent works thus far. In order to bridge the large gap, we have designed user-friendly specification environments for FDTs. The outlines of SEGL (Specification Environment for G-LOTOS), CBP (Concept-Based Programming environment) and MBP (Model-Based Programming environment) are described. The effectiveness of software development under such an environment is demonstrated using application examples from OSI and non-OSI protocols.

This paper describes a verification scheme for service specifications and presents verification results for prototype system. Verified specifications are described by information sequence charts, which describe the communicating states between users and the messages between a user and a network. The verification scheme consists of two steps: macro sequence verification, which treats rough transitions of states, and transition procedure verification, which treats procedure of all messages. A prototype verification system demonstrates that this scheme can detect about 90% of errors in a specification within 4.4 seconds.

A specification formalism for business application software is presented. Our approach is to investigate specification documents which are actually used in development projects of business applications in banking, insurance, and government systems. Since the specification documents are prepared mainly for users' review for the developing software, the representation of the documents is designed to be easy to understand for users, only in business terminology without losing a certain level of formality. Also, to avoid redundancy of the specification, there are some implicit assumptions in the specification. We have analyzed some commonality of these assumptions hidden in specification documents and are trying to construct a language by formalizing the underlying system model.

A Ge/Si structure grown by chemical vapor deposition (CVD) is angle-lapped and characterized by the micro-Raman spectroscopy. Near the interface, the phonon mode due to the Si-Ge bond is clearly observed, which indicates that a SiGe alloy is formed by the solid-phase interdiffusion at the interface. The thickness of the interfacial alloy layer is about 0.2 µm. Amount of residual strain is estimated by comparing the measured phonon frequencies with those predicted from the composition profie, but the shift due to the residual strain is not appreciable. Both the interdiffusion at the interface and the nearly complete relaxation of the lattice mismatch are attributed to the high growth temperature of the CVD sample.