This paper presents the theoretical analysis of subband adaptive array combining cyclic prefix transmission scheme (SBAA-CP) in multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). An example of implementing SBAA-CP as a software antenna is also presented.

This paper proposes and investigates a coding and decoding scheme to achieve adaptive channel coding using a Finite State Machine (FSM) for Software Defined Radio (SDR). Adaptive channel coding and decoding systems that can switch between different coding rates and error correcting capabilities in order to adapt to changing applications and environments, are effective for SDR. However, in these systems, a receiver cannot always select the correct decoder which causes decoding errors, usually referred to as Decoder-Selection-Errors (DSE). We propose a trellis encoder estimation scheme that compensates for this problem. This scheme uses the circuit of FSM to limit the encoder transition and the Viterbi algorithm for maximum likelihood trellis encoder estimation. Computer simulations are applied for evaluating the DSE rate, the Bit Error Rate (BER) and Throughput of the proposed scheme in comparison with a conventional scheme.

Intensive accesses to a web server causes its response delay and/or service suspension. We propose, to solve the problem in this paper, a service model for web servers grounded upon admission control and call waiting service, which are common approaches to designing telephone systems. Software architecture which consists of a front-end server and child servers is also designed based on the service model. Through performance evaluation for an implementation of the architecture, it is shown that the overall throughput becomes much better by keeping child web servers from overload. We drew a conclusion that the architecture enhances flexibility of a resulting software with discussions from the extensibility view.

Software with design flaws increases maintenance costs, decreases component reuse, and reduces software life. Even well-designed software tends to deteriorate with time as it undergoes maintenance. Work on restructuring object-oriented designs involves estimating the quality of the designs using metrics, and automating transformations that preserve the behavior of the designs. However, these factors have been treated almost independently of each other. A long-term goal is to define transformations preserving the behavior of object-oriented designs, and automate the transformations using metrics. In this paper, we describe a genetic algorithm based restructuring approach using metrics to automatically modify object-oriented designs. Cohesion and coupling metrics based on abstract models are defined to quantify designs and provide criteria for comparing alternative designs. The abstract models include a call-use graph and a class-association graph that represent methods, attributes, classes, and their relationships. The metrics include cohesion, inheritance coupling, and interaction coupling based on the behavioral similarity between methods extracted from the models. We define restructuring operations, and show that the operations preserve the behavior of object-oriented designs. We also devise a fitness function using cohesion and coupling metrics, and automatically restructure object-oriented designs by applying a genetic algorithm using the fitness function.

This paper considers a software reliability model which allows for two types of imperfect debuggings at each failure of the software system. For one type of imperfect debugging, a fault that causes the failure is imperfectly debugged without altering the fault contents of the software system. For the other type of imperfect debugging, the fault is not only imperfectly debugged, but also a new fault is generated and introduced into the system. The probability of perfect debugging is assumed to be an increasing function of the number of debuggings performed prior to the current failure of the system. Based on the software reliability model presented, we consider three profit models to determine the optimal software release times which maximize the expected software profit. These models consider: (1) constant life cycle, (2) random life cycle, (3) random life cycle and penalty cost which is imposed when the software is delivered late. The optimal release times are shown to be finite and unique. Numerical examples are provided for illustrative purposes.

Agent-based computing has been advocated by many researchers and software developers as a promising and innovative way to model, design and implement complex Web-related applications. KODAMA (Kyushu university Open & Distributed Autonomous MultiAgent) project, which is described in this paper, is our endeavour to advance both the technology and engineering of well-known multiagent systems. In particular, we have noted that software agents might be the potential solution to many problems faced by today's Web. However, building a high-quality, large-scale multiagent system, which can operate in open environments, is a great challenge. So far, we have devoted a lot of effort to design and implement a generic agent architecture, a hierarchical agent community structure, and an independent network communication middleware. To ensure that KODAMA can be used to create Web-agent applications, its network communication performance and a prototype distributed database retrieval system have been tested. The result shows that KODAMA is suitable for developing network-aware applications.

Properly representation of the complexity of class structure will be useful in object oriented software developments. Although some class complexity metrics have been proposed, they have ignored directions of coupling relationships among methods and attributes, such as whether a method writes data onto an attribute or reads data from the attribute. In this paper, we use a directed graph model to represent such coupling relationships. Based on the directed graph model, we propose a metric of class structural complexity. The proposed metric satisfies necessary conditions of complexity metric suggested by Briand and others. The following fact is showed by experimental data of Java classes. While the proposed metric follows a conventional metric, the proposed metric can capture an aspect of class structural complexity which is lost by the conventional one.

The group organization used for group learning in a knowledge intensive domain like software development affects educational achievement. This paper proposes a group organization system for software engineering education done through group learning. The organizational problem itself is defined and why a Genetic Algorithm (GA) is an appropriate means of solving this problem is explained. This system is a Web application developed with open source software and runs on an open source software platform. Based on the group organization data collected from actual classes, we generated various group organizations by using different strategy parameter values. We then gave a questionnaire to actual students asking them which solution produced the fairest group organization. The replies received revealed that the candidate solution that set greater weight on leadership capability and system analysis capability was the fairest.

Network traffic characteristics impacts directly network performance, and resource allocation policies. In this work, we introduce a multi-agent system, that manages the performance of web servers with minimal cost of mirroring. In our proposed system each web server is viewed as a software agent that perceives its environment by monitoring its traffic. The goal of the agent is to manage the performance, using cooperative mirror servers, while minimizing the cost of mirroring. Communication between the agents enables each web server to decide about its future actions, which is whether to share its load with the cooperative mirror servers, and how much load to assign to them. The architecture of a software agent that is intended to manage the performance of a web server, is elaborated and its different modules are described. Also a set of cooperative agents is defined, that form a multi-agent system and is intended to assure maintaining the performance with minimal cost of mirroring. The experimental results presented in this article illustrates the effectiveness of the proposed system.

As a center of mobile multimedia of the 21st century, it is very much looking forward to explosion of R&D and business of the next generation of mobile communication systems and the ITS (Intelligent Transport Systems) because ITS will enable information-oriented in the field of the road, traffic and vehicles, by using the most advanced technologies of mobile communications and devices, for the various purposes such as decrease of the traffic accident, the reduction of traffic jam, the increase in efficiency of the logistics and the harmony with the earth environment. This invited paper will first briefly introduce evolution of mobile communications and ITS in ministries, industries and academia in Japan. Then core communication technologies for ITS will be overviewed such as spread spectrum CDMA, adaptive antenna array, and software radio or software defined radio. Demands of SoC (System on a Chip) to carry out the core technologies will be addressed.

In this paper, we discuss an IF image rejection system with variable bandwidth and center frequency. The system is consists of a pair of frequency mixers multiplied by the complex sinusoid and a complex analog filter. By employing the complex leapfrog structure using OTA-C configuration and the frequency transformation from the normalized LPF, the proposed system is capable of variable bandwidth and center frequency characteristics. SPICE simulations result more than 43 [dB] image rejection is achieved for 6 [kHz] and 12 [kHz] bandwidths at 50 [kHz] IF.

This paper reports on clich and related mechanisms appearing in a process of human design of software. During studies on human design knowledge, the authors found frequent instance of same pattern of detailing, named clich. In our study, clich is an intermediate level of design knowledge, during a hierarchical detailing step, residing in between simple reuse and creation by micro design rules, which have already been reported. These three kinds of design knowledge are of various types and have different complexities. Discussions on them, focusing on clich type, with procedures of formation of a simple clich skeleton and generation of a clich are given. The studies show a working model of Zipf's principle, and are some trials to reveal a more detail of human designs.

Today software piracy is a major concern to electronic commerce since a digitized product such as software is vulnerable to redistribution and unauthorized use. This paper presents an enhanced electronic software distribution and software protection model. Authentication scheme of the proposed model is based on zero-knowledge (ZK) proof which requires limited computation. The proposed model considers post installation security using authentication agent. It prevents software piracy and illegal copy. It also provides secure and efficient software live-update mechanism based on traitor tracing scheme. Even if software or personal key is copied illegally, a merchant can trace back to its original owner from the electronic license and personal key. The proposed model provides security and reasonable performance and safety.

This letter proposes a hardware/software partitioning algorithm for digital signal processor cores with two register files. Given a compiled assembly code and a timing constraint of execution time, the proposed algorithm generates a processor core configuration with a new assembly code running on the generated processor core. The proposed algorithm considers two register files and determines the number of registers in each of register files. Moreover the algorithm considers two or more types of functional units for each arithmetic or logical operation and assigns functional units with small area to a processor core without causing performance penalty. A generated processor core will have small area compared with processor cores which have a single register file or those which consider only one type of functional units for each operation. The experimental results demonstrate the effectiveness and efficiency of the proposed algorithm.

A system level approach for a memory power reduction is proposed in this paper. The basic idea is allocating frequently executed object codes into a small subprogram memory and optimizing supply voltage and threshold voltage of the subprogram memory. Since large scale memory contains a lot of direct paths from power supply to ground, power dissipation caused by subthreshold leakage current is more serious than dynamic power dissipation. Our approach optimizes the size of subprogram memory, supply voltage, and threshold voltage so as to minimize memory power dissipation including static power dissipation caused by leakage current. A heuristic algorithm which determines code allocation, supply voltage, and threshold voltage simultaneously so as to minimize power dissipation of memories is proposed as well. Our experiments with some benchmark programs demonstrate significant energy reductions up to 80% over a program memory which does not employ our approach.

This paper presents an enhancement of a software project simulator to perform risk prediction with cost estimation capability. So far, we have developed a software project simulator to simulate software development projects. In this simulator, a development process was described using Petri net model, and it was applied to some actual project data in a certain company successfully. On the other hand, we have also presented a risk predicting system to find "risky" projects by statistical analysis on risk questionnaire for project managers. In this approach, only the probability to be risky was calculated for a project. Thus, the managers in the company wanted to know a concrete proof why a software project becomes risky. In this paper, to present the proof that a software project becomes risky, we try to enhance the previous project simulator so that the simulator can deal with risk factors. To consider the risk factors, we modify the previous simulator so that both the fluctuation of skill level and the deadline pressure can be represented by the parameters in the simulator. By using a case study, we confirm that the enhanced simulator can estimate the development cost under some typical risks. As a result, we can expect that the simulator shows how much the development cost of a risky project exceeds an estimate.

Hardware/software partitioning is one of the key processes in a hardware/software cosynthesis system for digital signal processor cores. In hardware/software partitioning, area and delay estimation of a processor core plays an important role since the hardware/software partitioning process must determine which part of a processor core should be realized by hardware units and which part should be realized by a sequence of instructions based on execution time of an input application program and area of a synthesized processor core. This paper proposes area and delay estimation equations for digital signal processor cores. For area estimation, we show that total area for a processor core can be derived from the sum of area for a processor kernel and area for additional hardware units. Area for a processor kernel can be mainly obtained by minimum area for a processor kernel and overheads for adding hardware units and registers. Area for a hardware unit can be mainly obtained by its type and operation bit width. For delay estimation, we show that critical path delay for a processor core can be derived from the delay of a hardware unit which is on the critical path in the processor core. Experimental results demonstrate that errors of area estimation are less than 2% and errors of delay estimation are less than 2 ns when comparing estimated area and delay with logic-synthesized area and delay.

Over recent years, "Internet-able" applications and architectures have been used to support domains where there are multiple interconnected systems that are both decentralized and autonomous. In enterprise-level data management domains, both the schema of the data repository and the individual query needs of the users evolve over time. To handle this evolution, the resulting architecture must enforce the autonomy in systems that support the client needs and constraints, in addition to maintaining the autonomy in systems that support the actual data schema and extraction mechanisms. At the MITRE Corporation, this domain has been identified in the development of a composite data repository for the Center for Advanced Aviation System Development (CAASD). In the development of such a repository, the supporting architecture includes specialized mechanisms to disseminate the data to a diverse evolving set of researchers. This paper presents the motivation and design of such an architecture to support these autonomous data extraction environments. This run-time configurable architecture is implemented using web-based technologies such as the Extensible Markup Language (XML), Java Servlets, Extensible Stylesheets (XSL), and a relational database management system (RDBMS).

In this letter, we focus on achieving the reconfiguration of a multi-rate interference cancellation (IC) scheme via a software radio implementation. In the proposed multi-rate IC scheme, the estimates of each user signal are updated every cancellation stage with more clean signal, which are used in the next stage to yield more reliable estimates.

The software rejuvenation is one of the most effective preventive maintenance technique for operational software systems with high assurance requirement. In this paper, we propose the workload-based software rejuvenation scheme for a server type of software system, and develop stochastic models to determine the optimal software rejuvenation schedules for some dependability measures. In numerical examples, we evaluate quantitatively the performance of workload-based software rejuvenation scheme and compare it with the time-based rejuvenation scheme.