With the evolution of sixth generation (6G) technologies and Internet of Things (IoT), base stations and IoT devices are deployed densely to achieve the ultra-high data rate, resulting in the scarcity of spectrum resource. To tackle it, we study a cell-free symbiotic radio network (CF-SRN) that consists of the cell-free network (CFN) and IoT network, and includes multiple access points (APs), multiple backscatter devices (BDs), and a single receiver. APs collaboratively transmit primary radio frequency (RF) signals to the receiver, and BDs split the energy of primary RF signals to perform backscatter communication, and energy harvesting. Existing works focus on the SRN with commensal symbiotic radio (CSR) or parasitic symbiotic radio (PSR) setup, while we design a hybrid CSR-PSR setup to balance the tradeoff between primary communication and backscatter communication in the CF-SRN. Based on the design, we formulate the sum backscatter throughput maximization problem by optimizing the time allocation vector, beamforming vectors of APs and BDs, and reflection coefficients of BDs, subject to the minimum sum primary throughput constraint. Due to the coupling relationship among high-dimensional variables, we decompose the formulated problem into time allocation optimization (TAO) subproblem, beamforming optimization (BO) subproblem, and reflection coefficient optimization (RCO) subproblem. For TAO subproblem, we use a linear programming method to obtain the optimal solution. For BO subproblem and RCO subproblem, we propose a block coordinate descent-based semi-definite relaxation and successive convex approximation (BSS) algorithm. Simulation results validate the superiority of the BSS algorithm and hybrid CSR-PSR setup.

This paper investigates a dynamic heterogeneous mobile edge computing network (HMECN), where mobile devices (MDs) could offload their full tasks to a small base station (SBS) directly or the macro base station (MBS) in direct or relay mode. As age of information (AoI) is a comprehensive and accurate metric to capture the freshness of computation results, we formulate a long-term weighted sum AoI (LWSA) minimization problem in the HMECN by jointly optimizing the offloading decisions of MDs as well as the bandwidth and computation resource allocation of all base stations, subject to energy, delay and peak AoI constraints. To address the formulated non-convex mixed integer nonlinear programming problem, we decompose it into the offloading decision optimization (ODO) top-problem and the resource allocation optimization (RAO) sub-problem. Based on the decomposition, we propose a federated learning (FL)-assisted hybrid DRL and convex approach that is comprised of a safe multi-agent DRL algorithm, convex optimization and FL. The ODO top-problem is solved by the safe multi-agent DRL algorithm, which strictly ensures that the actions of each agent do not exceed its energy constraint and then paves the way for using convex optimization to solve the RAO sub-problem. FL is used to alleviate the training instability problem aggravated by multi agent settings via breaking the limitation of partial knowledge for each individual agent. Simulation results demonstrate the superiority of the proposed approach in terms of the LWSA, convergence, scalability and robustness in dynamic environments.

Space-air-ground integrated network (SAGIN) represents a pivotal architecture for the future evolution of global mobile communications. However, its inherent high dynamics and stochastic nature pose significant challenges to conventional routing mechanisms. Moreover, the vast spatial-scale openness of SAGIN makes it particularly vulnerable to eavesdropping attacks. This paper presents a novel sleeping multi-armed bandit (SMAB) framework, designed to enable secure routing in SAGIN. Specifically, we first establish channel models for all types of links in SAGIN. Then, we theoretically analyze the statistical properties of secrecy capacity and end-to-end (E2E) delay for message transmission over arbitrary routes, and formulate the secure routing problem to maximize cumulative secure transmission throughput under the delay constraint. The uncertainty in the network state of SAGIN, along with the complexity of the optimization objective and constraint (non-convex, non-linear, and coupled), renders the solution to the secure routing problem highly intractable. To this end, we leverage the MAB model to transform the secure routing problem into a budget-constrained arm-pulling problem and introduce the “sleeping” mode to capture route unavailability due to intermittent link failures. To effectively balance route exploration and exploitation, we further apply the upper confidence bound (UCB) method to design the SMAB-based secure routing algorithm (SMAB-SR), and derive its regret upper bound theoretically. Finally, extensive simulations verify that the SMAB-SR algorithm exhibits significant advantages in E2E secure transmission throughput compared to benchmarks and can maintain highly effective across various SAGIN configurations.

The deep learning-based semantic communication system (DeepSC) is designed to improve the efficiency and accuracy of information transmission, by leveraging joint source-channel coding techniques to extract relevant semantic features. However, existing research on attack methods targeting DeepSC has primarily focused on text and image domains, leaving the speech domain largely unexplored. To this end, this paper proposes Iterative Semantic Gradient Update (ISGU), a novel approach for crafting physical layer adversarial attacks on DeepSC for speech transmission (DeepSC-ST). Specifically, we introduce a joint loss that combines the semantic similarity loss with Connectionist Temporal Classification loss to expedite the generation process of targeted attacks against the DeepSC-ST. In addition, we design an algorithm to generate adversarial examples, enhancing their imperceptibility by meticulously controlling the perturbation power added to the input speech. Extensive experiments indicate that ISGU is capable of rapidly generating highly covert adversarial examples, with a notably high attack success rate.

Semantic communication, an emerging AI-driven communication paradigm, offers great potential for multimodal data delivery in space-ground integrated networks (SGINs). However, the dynamic nature of SGINs presents severe challenges for path selection, making it difficult to ensure the quality of service (QoS) at the semantic level. To this end, we propose in this paper a novel path selection scheme in space-ground multimodal semantic communication networks based on the sleeping multi-armed bandit (MAB) approach. Specifically, we first model the approximate semantic entropy and semantic rate, formulating an optimal path selection problem that integrates link state information and semantic data transmission volume. Then, we convert the path selection problem into a sleeping MAB problem and meticulously design an upper confidence bound (UCB)-based algorithm to solve it, called Periodic Probability Sleeping Path Selection (PPSPS), which copes with the dynamic feature of SGINs. We further theoretically verify the bounded regret of the PPSPS algorithm, indicating that it can ensure good semantic communication QoS. Simulation results demonstrate the superiority of the proposed path selection scheme compared to traditional reinforcement learning methods.

In mobile edge networks, federated learning (FL) has garnered substantial attention as a distributed machine learning framework with significant advantages for protecting user privacy. Due to the limited resources of wireless bandwidth, such FL-based applications are quite susceptible to Distributed Denial-of-Service (DDoS) attacks. Prior solutions either rely on centralized mechanisms that require complete information about all participants or are customized to specific systems. However, these solutions are either obsolete or ineffective given the new properties of FL. In this work, we first formulate a DDoS mitigation problem on bandwidth allocation for FL within mobile edge networks. Considering interactions between various network components and users, we propose anEvolutionaryGame andDouble-sidedAuction-based framework, termed EGDA, which consists of EG-based and DA-based mechanisms for user-bandwidth allocation (UBA) and server-bandwidth allocation (SBA), respectively. Specifically, to address DDoS attacks on UBA, we design an EG-based approach with minimum latency for FL under limited information. The proposed EG-based allocation algorithm is proven to be stable and achieve the evolutionary equilibrium. To mitigate DDoS attacks on SBA, we study an approach of DA with social welfare maximization while protecting the privacy of participants. Then, an iterative DA-based allocation algorithm is developed to be convergent and satisfy desirable economic properties. Extensive evaluation demonstrates that EGDA mitigates DDoS attacks effectively and efficiently.

Warden collusion represents a hazardous threat to wireless covert communication, where wardens can combine their observations to perform a more aggressive detection attack. This paper investigates the impact of warden collusion on covert communication in a multi-antenna wireless network consisting of one source, one destination, multiple wardens and interferers. By employing the techniques of Laplace Transform and Cauchy Integral Theorem, we first establish a framework to model the aggregate interference distribution (AID) for covert communication in the network under the typical additive white Gaussian noise (AWGN) and Rayleigh fading channels. Based on the AID results, we then develop theoretical models to reveal the inherent relationship between the collusion intensity and fundamental communication metrics in terms of the covert outage probability, connection outage probability and covert throughput. With the help of these models, we further explore the covert throughput optimization problems and present extensive numerical results to illustrate the impact of warden collusion on the covert throughput under both channel models.

Distributed Vehicle Sharing System (DVSS) leverages emerging technologies such as blockchain to create a secure, transparent, and efficient platform for sharing vehicles. In such a system, both efficient matching of users with available vehicles and optimal pricing mechanisms play crucial roles in maximizing system revenue. However, most existing schemes utilize user-to-vehicle (two-sided) matching and pricing, which are unrealistic for DVSS due to the lack of participation of service providers. To address this issue, we propose in this paper a novel Three-sided stable Matching with an optimal Pricing (TRIMP) scheme. First, to achieve maximum utilities for all three parties simultaneously, we formulate the optimal policy and pricing problem as a three-stage Stackelberg game and derive its equilibrium points accordingly. Second, relying on these solutions from the Stackelberg game, we construct a three-sided cyclic matching for DVSS. Third, as the existence of such a matching is NP-complete, we design a specific vehicle sharing algorithm to realize stable matching. Extensive experiments demonstrate the effectiveness of our TRIMP scheme, which optimizes the matching process and ensures efficient resource allocation, leading to a more stable and well-functioning decentralized vehicle sharing ecosystem.

The energy harvesting D2D-enabled cellular network (EH-DCN) has emerged as a promising approach to address the issues of energy supply and spectrum utilization. Most of existing works mainly focus on the throughput, while the information freshness, which is critical to the time-sensitive applications, has been rarely explored. Considering above facts, we aim to develop an optimal mode selection and resource allocation (MSRA) policy that maximizes the long-term overall throughput of a time-varying dynamic EH-DCN, subject to an age of information (AoI) constraint. As the MSRA policy involves both continuous variables (i.e., bandwidth, power, and time allocations) and discrete variables (i.e., mode selection and channel allocation), the optimization problem is proved to be nonconvex and NP-hard. To solve the nonconvex NP-hard problem, we exploit a deep reinforcement learning (DRL) approach, called MSRA twin delayed deep deterministic policy gradient (MSRA-TD3). The MSRA-TD3 employs a double critic network structure to better fit the reward function, and could effectively mitigate the overestimation of Q-value in deep deterministic policy gradient (DDPG), which is a classical DRL algorithm. It is worth noting that in the design of the MSRA-TD3, we use the throughput of user equipments (UEs) at the previous time slot as a state to bypass the channel state information estimation resulting from the time-varying dynamic environment, and take the weights of throughput and AoI penalty into the reward function to evaluate two performance. Simulations demonstrate that the established MSRA-TD3 algorithm achieves better performance in terms of throughput and AoI than comparison DRL algorithms.

Air-ground integrated networks (AGINs) are promising to provide wide-coverage, high-capacity, and low-latency communication services, and thus have been attracting increasing attention from industry and academia recently. However, the open and dynamic nature of AGINs makes them vulnerable to eavesdropping attacks, posing a major challenge in ensuring end-to-end information transmission security. To this end, we propose in this paper a secure routing scheme in AGINs based on the multi-armed bandit (MAB) approach. Specifically, we first model the secrecy transmission performance for the ground-to-ground links and ground-to-air links. Based on this, we then formulate the end-to-end secure route selection problem and convert it into a budget-constrained MAB problem, where each arm is associated with a corresponding reward and cost. We further design a Secure Route Upper Confidence Bound (SRUCB) algorithm to solve the MAB problem, which copes with the scenario where the locations of eavesdroppers and jammers are unknown, and can be proven to have a bounded regret. Numerical results demonstrate the superiority of the proposed routing scheme compared to several online learning algorithms.

Benefiting from the booming of Big Data and artificial intelligence (AI) technologies, data-as-a-service is gradually transforming into knowledge-as-a-service. Extracting knowledge from massive raw data is becoming a popular paradigm to save network resources and improve efficiency, and establishing knowledge markets is receiving increasing attention from academia and industry. In this paper, we propose a one-stop knowledge acquisition ecosystem termed BWKA that covers the whole process from upper-layer knowledge trading to underlying knowledge generation. In the knowledge trading process, the knowledge-as-a-service platform (KSP) is the buyer and publishes knowledge demands to multiple local knowledge sellers (LKSs). In the knowledge generation process, each LKS aggregates data from its sensors and then trains data into knowledge according to the KSP's requirements. We resort to blockchain technology and provide a series of tailored operating rules and functions to protect the truthfulness of data gathering and the fairness of knowledge trading. In addition, we introduce incentive mechanisms to stimulate selfish and rational entities in the BWKA ecosystem to participate in knowledge acquisition. To analyze the strategic interactions among entities theoretically, we develop a nested hierarchical game model, where the upper-layer knowledge trading is evaluated based on the Contract Theory, and the lower-layer knowledge generation is formulated as a two-stage Stackelberg game. By solving the nested hierarchical game in a backward inductive way, we identify the optimal strategy for each entity in closed form. Experiments on the Ethereum blockchain and simulation results demonstrate the practical operability and outstanding performance of the BWKA ecosystem.

This paper studies the possible physical layer security (PLS) enhancement in a wiretapped two-way relay system from utilizing the reconfigurable intelligent surface (RIS) and beamforming techniques. We first jointly apply the RIS and beamforming (RIS-B) to develop an advanced secure transmission scheme for the system, and conduct related theoretical modeling for the system secrecy sum rate (SSR) under the RIS-B scheme. We then apply the theories of alternating optimization, successive convex approximation, augmented Lagrange method and the quasi-Newton method to devise both the optimal and low-complexity sub-optimal frameworks to identify the optimal settings of RIS phase shifts and beamforming matrix of the RIS-B scheme for SSR maximization. We further investigate a special case when solely the RIS technique is applied for SSR performance enhancement. With the help of Charnes-Cooper transformation, semidefinite programming and Gaussian randomization, we devise an optimization framework to identify the optimal settings of RIS phase shifts for SSR maximization. Finally, extensive numerical results are provided to illustrate the efficiency of the RIS and RIS-B schemes in PLS enhancement in comparison with the conventional channel-capacity-based secure transmission.

Mobile crowdsensing (MCS) has emerged as a popular and promising paradigm for solving challenging problems by utilizing collective wisdom and resources. However, the system architecture and operational rules for MCS have not been well-defined, and obtaining accurate and reliable results from conflicting data collected by workers is difficult due to discrepancies in sensor quality and privacy protection requirements. In this paper, we combine the methodologies of Dynamic Truth Discovery (DTD), Combinatorial Multi-Armed Bandit (CMAB), and Multi-Attribute Reverse Auction to develop a novel MCS ecosystem, with the objective of maximizing the sensing accuracy-aware utility under the budget constraint. We first establish the data collection model by jointly considering the task completion duration as well as the deviation caused by both endogenous errors and privacy protection-oriented injected noise. Then, we theoretically evaluate the accuracy of truth discovery and quantify the contribution of each worker to MCS to form the worker selection criterion. As the qualities of workers are initially unknown, the platform faces the exploration-exploitation dilemma. Therefore, we apply CMAB to transform the worker recruitment problem into a combinatorial arm-pulling problem and elaborately design an Upper Confidence Bound (UCB) algorithm to achieve a desirable exploration-exploitation tradeoff. Moreover, we design an auction-based payment method for the platform, stimulating workers to provide their quoted price honestly while enabling individual rationality. Extensive simulations and comparison results demonstrate the feasibility and effectiveness of our proposed MCS ecosystem.

As a new distributed data training framework, federated learning (FL) has attracted increasing attention owing to its advantages of preserving data privacy and low communication cost. However, in a wireless FL network, due to the limited bandwidth resources, when a large number of clients participate in FL, the communication burden is too heavy. Therefore, efficient bandwidth allocation is critical to facilitate the application of wireless FL. In this paper, we investigate bandwidth allocation in wireless FL networks with the objective of minimizing the latency of FL services. We first analyze and formulate the latency minimization problem. Then, considering that the computing and transmitting capabilities of each client cannot be completely and truly acquired, we develop an evolutionary game (EG) framework to model the dynamic process of bandwidth allocation in wireless FL. We further show the optimal bandwidth allocation solution is equivalent to the evolutionary equilibrium (EE) obtained by the replicator dynamics in the EG model, and prove the EE is asymptotically stable. With the help of these results, we propose the EG-based bandwidth allocation algorithm, which enables the latency of FL services to be reduced by performing the replicator dynamics iteratively. Numerical simulations are provided to demonstrate the evolutionary behaviors in the EG-based bandwidth allocation Algorithm.

In the era of big data, the unprecedented growth of data has spawned the commercial application of data trading markets in the Internet of Vehicles (IoV), while also posing challenges to their economic feasibility. In this paper, we propose a data-energy trading architecture in IoV consisting of a market operator, electric vehicles (EVs), and roadside units (RSUs), where RSUs exchange energy for data collected by EVs, and the market operator solves the data/energy allocation problem to maximize social welfare. However, due to the information asymmetry and fragmentation in the market, it is difficult to determine the optimal data and energy trading amount. To this end, we design an iterative double-sided auction (IDA) mechanism to regulate the interactive behaviors among the trading entities, where the market operator gathers local information from RSUs and EVs, and gradually adjusts the submitted bids of two sides to reach the desired payment and reward rules. The proposed IDA-based data-energy trading algorithm is convergent and satisfies the economic properties of efficiency, incentive compatibility, individual rationality, and budget balance. Numerical results demonstrate the performance of the proposed IDA-based data-energy trading architecture in IoV.

In the era of big data, the unprecedented growth of data has been regarded as an important asset and the commercial application of data acquisition markets has emerged accordingly. With the advancement of vehicle manufacturing and sensor technologies, a large amount of data can be collected and stored in electric vehicles (EV), making the data acquisition scenario gradually extend to the Internet of Vehicles (IoV), and thus the corresponding operational rules and economic feasibility need to be fully investigated there. In this paper, we focus on a general IoV-oriented data acquisition market that consists of a data center, multiple EVs, multiple roadside units (RSUs), and a market operator (broker), with the objective of social welfare maximization (SWM) by identifying the optimal data task allocation. However, due to the inherent information asymmetry and fragmentation in such a market, it is not feasible to solve the SWM problem directly. To this end, we propose an iterative double-sided auction (IDA) mechanism, which leverages the self-interested feature of RSUs and EVs to decompose the SWM problem, enabling every participant to make decisions in a distributed manner under the broker’s coordination. A complete set of operational rules covering the data task allocation, bidding, payment, and reimbursement are elaborately designed to achieve SWM, and energy is adopted as the pricing “currency”, such that an IDA-based Data-Energy Transaction (IDADET) ecosystem is established in IoV. We verify the economic feasibility of the proposed IDADET ecosystem by showing its convergence and desirable properties of individual rationality, budget balance, incentive compatibility, and economic efficiency. In addition, considering the psychological effects of practical market participants, we make amendments to the operational rules of the IDADET ecosystem from the behavioral economics perspective, aiming to ensure its long-term well-functioning. Extensive numerical results are presented to show the performance of the IDADET ecosystem and demonstrate its advantages in terms of economic properties, operational feasibility, fast convergence, and market social welfare.

In this paper, we focus on a multi-hop decentralized wireless network consisting of legitimate nodes, adversary wardens, and friendly but selfish jammers, and investigate the routing design for achieving covert communication. For a pair of source and destination nodes, we first provide theoretical analysis for a given route between them to reveal how the covertness performance is related to the jamming power of jammers in the network. Then, we design an incentive mechanism that stimulates selfish jammers to supply artificial jamming to protect communication covertness, by granting them rewards from the source. A two-stage Stackelberg game framework is developed to analyze the strategic interactions between the source and jammers, and so as to determine the optimal settings of rewards and jamming power. Based on these results, we formulate a shortest weighted path-finding problem to identify the optimal route for covert communication between the source and destination, which can be solved efficiently by employing Dijkstra's algorithm. Simulation results demonstrate the performance of the proposed incentive routing scheme.

This paper investigates secure communication in a two-hop relaying system based on physical layer security. The relay employs time-switching simultaneous wireless information and power transfer (SWIPT) to harvest energy and receive information from the source, and then transmits the source’s information and its own information to the destination. A passive eavesdropper exists and wiretaps information transmission over both hops. Under the general system configuration, we first provide performance modeling to reveal the secrecy rate of source and relay as well as identify their utilities. Then, we analyze the hierarchical competition behaviors between the source and relay from a game-theoretic perspective. In particular, we develop a Stackelberg game-based analytical framework to determine the optimal strategies for the source and relay by deriving the Stackelberg equilibrium. Furthermore, we summarize the feasible conditions of utilizing SWIPT-enabled relaying for secure communication and propose the end-to-end transmission scheme accordingly. Extensive numerical results are presented to demonstrate the performance of the proposed SWIPT-enabled relaying system.

This paper explores the joint secrecy and delay guarantees based on opportunistic jamming and link selection in a wireless relay system consisting of a source, a destination, multiple buffer-aided relays and a passive eavesdropper wiretapping over both hops. Based on the information of link state and buffer status, we design a novel transmission scheme based on link selection and jammer selection, which dynamically grants transmission links different priorities for packet delivery, such that the constraints on both secrecy outage probability and packet delay are jointly satisfied. To understand the performance of the new scheme, we then apply the bitmap technique and Markov chain theory to develop a complete theoretical framework for the modelling of three fundamental metrics, namely reliability outage probability, packet discarding probability and secrecy/delay constrained throughput (SDT). Finally, we provide extensive simulation and numerical results to validate our theoretical modelling, as well as to demonstrate that the proposed scheme is superior to the benchmarks in terms of SDT.

This paper presents the concept of Digital Ji-in, a framework for managing permanent digital identifiers whose structure is based on a peer to peer network. The origin of the term Digital-Ji-in is explained in the paper. We describe several types of identifiers and explain why their management is already an important issue. We show that some identifiers have been reused, creating significant problems. We propose a framework for maintaining identifier information safely over a long period of time. We present its structure based on a secure network of peers. We also describe some use cases of this framework. However, as only identifiers are recorded mechanically, problems may arise if data should be associated with them. We discuss this issue at the end of the paper.

This paper focuses on the multiple-input-multiple-output (MIMO) two-way relay system with an untrusted relay and investigates its secure and energy-efficient precoding design issue based on the physical layer security technology. We first provide theoretical modeling for the index of secrecy energy efficiency (SEE) and formulate the optimal precoding design for SEE maximization (SEEM) as a high-dimensional non-convex programming problem. By exploring the techniques like fractional programming, alternate optimization and semi-definite programming, we then develop a hierarchical theoretical framework to solve the SEEM problem and thus to identify the optimal precoding designs for the source and relay. Furthermore, we demonstrate the proposed theoretical framework is also applicable to the problem of precoding design for secrecy sum rate maximization. Finally, with the help of generalized singular value decomposition, we propose a sub-optimal relay precoding design scheme with significantly lower computational complexity. Extensive numerical results provided in the paper indicate that the proposed schemes can remarkably improve the SEE performance in MIMO two-way untrusted relay systems.

This paper focuses on the QoS-aware secure routing design based on the physical layer security technology for a multi-hop wireless network consisting of legitimate nodes, malicious eavesdroppers, and selfish jammers. We first provide theoretical modeling for a given route to reveal how its end-to-end security/QoS performance is related to the transmitting power of legitimate nodes along the route and the jamming power of jammers in the network. We then design an incentive mechanism that stimulates jammers to generate artificial jamming for security enhancement, and also develop a non-cooperative game framework to resolve the jamming power setting issue here. Based on the security/QoS performance modeling of the route and jamming power setting, we further propose a theoretical framework to determine the optimal transmitting power of nodes along the route such that its optimal transmission security can be achieved under a QoS constraint. Finally, with the help of the power setting results of the given route, we formulate a shortest weighted path-finding problem to identify the optimal route for data delivery in the network, which can be solved by employing the Bellman-Ford or Dijkstra's algorithm. It is demonstrated that the proposed routing scheme is individually rational, stable, distributed and computationally efficient.

This article investigates the secure communication in a two-hop cooperative wireless network, where a buffer-aided relay helps forward data from the source to destination, and a passive eavesdropper attempts to intercept data transmission from both the source and relay. To ensure the transmission security and communication quality of service (QoS) of the system, we design novel link selection policies for two cases that the instantaneous channel state information is available or unavailable at the source node. For evaluating the system performance, we then derive the closed-form expressions of end-to-end secrecy outage probability, system throughput and secrecy throughput, respectively. Based on the theoretical performance analysis, we further explore the performance optimization issues, revealing the insightful tradeoffs between the transmission security and QoS. An iterative algorithm is developed to identify the optimal setting of link selection parameters, which is helpful for the practical configuration of link selection policies to satisfy various system performance requirements. Finally, we conduct simulations to validate our theoretical performance analysis, and also provide extensive numerical results to illustrate the efficiency of the proposed link selection policies for ensuring the secure communication in a two-hop cooperative network.

This paper focuses on a full-duplex multiple-input multiple-output two-way untrusted relay system, and investigates the optimal beamforming design of such system to maximize its secrecy sum rate (SSR) based on the physical layer security technology. We first provide the modeling of SSR under a general beamforming setting as well as the theoretical formulation of the optimal beamforming design problem. Based on the ideal assumption that the full channel state information is available, we then develop a novel theoretical framework to solve the optimal design problem and thus establish an upper bound on SSR, where the techniques of alternate optimization, fractional programming, semi-definite programming and barrier function method are jointly employed. With the consideration of the constraints in practical implementations, we further propose two sub-optimal beamforming design solutions based on either Wiener prediction or asymptotic approximation. The issue of how to reduce the computational complexity in the optimal relay beamforming design is also discussed in this paper. Finally, we present extensive numerical results to illustrate our theoretical findings and to demonstrate the performance of the proposed sub-optimal beamforming design solutions.

In order to get better results during brainstorming activities participants must respect some rules when they write notes about ideas and when they consider notes written by somebody else. We argue that the respect of these rules can be verified by a multi-agent system analyzing videos and notes produced by the participants in real time. This system can simplify the role of the meeting facilitator. Feedback is sent individually or is addressed globally to the entire team. This paper presents considerations about the necessity of rules, the structure of a multi-agent system for analyzing the respect of those rules and how experiments could show the level of acceptance by people of such a system. The goal of this prospective research is to add a non intrusive system during brainstorming sessions in order to enhance the quality of results.

In this paper, we investigate energy-efficient secure communications in an untrusted two-way relay network, where two source nodes exchange messages via an untrusted relay. Considering both security threats and energy limitation, the performance metric secure energy efficiency is defined as the ratio of the secrecy sum rate to the total power consumption. Our objective is to maximize the secure energy efficiency by jointly designing the source and relay beamformers. We first derive the expression of secure energy efficiency under a general beamforming configuration. Then, an iterative algorithm based on the techniques of alternate optimization, fractional programming, barrier function method and semi-definite programming, is proposed to find the optimal solutions of the source and relay beamformers. Our analysis shows that the proposed scheme can not only solve the problem of secure energy efficiency maximization but also be applicable for solving the problem of secrecy sum rate maximization. Simulation results demonstrate that the proposed scheme achieves a good gain in terms of secure energy efficiency.

Software-defined networking (SDN) not only lessens the burden of network operators but also accelerates the provision of high-quality services to various users by speeding up changes to the network configuration. Recently, Wireless Networking (WN) has gained importance as a social infrastructure to connect a large number of devices and cloud applications. Software definition technology for wireless networks is referred to as software-defined wireless networking (SDWN). We hereby propose a cognitive software-defined wireless networking (CSDWN) to enhance SDWN by applying a cognitive cycle to SDWN in addition to the development of a prototype to validate this concept.

This paper study the secure optimal QoS routing (SOQR) in wireless ad hoc networks (WANETs) based on the physical layer security techniques. Specifically, we consider a multi-hop WANET with malicious eavesdroppers and cooperative jammers, and formulate the SOQR as an optimization problem. To deal with this problem, we first derive the closed-form expressions of connection outage probability (COP) and secrecy outage probability (SOP) for any given end-to-end path, which serve as the performance metrics of communication QoS and transmission security, respectively. Then, we explore the minimum COP conditioned on that SOP is below a pre-specified threshold and obtain the corresponding achievable power allocation strategy. With the help of analysis of a given path, we further propose the SOQR algorithm which selects the secure path between a pair of source and destination nodes in a distributed manner to achieve the optimal QoS performance. Finally, numerical simulations are conducted to validate the efficiency of our theoretical results, as well as to illustrate the QoS-security tradeoffs.

By large tsunami damage due to the Great East Japan Earthquake, many existing network system stopped functioning in various factors. Even under such circumstances, some of the information communication method that including satellite communications, it was able to recover the Network Connectivity, actually quickly and effectively. Although there are some valid information communicating method in disaster, however the information communication method has a strong and weak points, when using each a single unit, it is not possible to follow the disaster area of the situations to be constantly changing. In addition, the emergency information communication system there may not be available in the battery out and do not know how to use in case of emergency. Therefore, it is important to design a systems available without a disaster by providing enough Network Capability. We develop a Never Die Network (NDN) system that is a new network system to achieve both the Network Capability in the normal and Network Connectivity in disaster based on the experience of Great East Japan Earthquake. In this paper, we propose a method for the system to autonomously derive the optimum packet flow by measuring the communication state such as throughput and packet loss in a system such as to considering multiple different access networks. We prepared a test bed that implements a prototype system, and evaluated based on a disaster scenario.

By large tsunami damage due to the Great East Japan Earthquake, many existing network system stopped functioning in various factors. Even under such circumstances, some of the information communication method that including satellite communications, it was able to recover the Network Connectivity, actually quickly and effectively. Although there are some valid information communicating method in disaster, however the information communication method has a strong and weak points, when using each a single unit, it is not possible to follow the disaster area of the situations to be constantly changing. In addition, the emergency information communication system there may not be available in the battery out and do not know how to use in case of emergency. Therefore, it is important to design a systems available without a disaster by providing enough Network Capability. We develop a Never Die Network (NDN) system that is a new network system to achieve both the Network Capability in the normal and Network Connectivity in disaster based on the experience of Great East Japan Earthquake. In this paper, we propose a method for the system to autonomously derive the optimum packet flow by measuring the communication state such as throughput and packet loss in a system such as to considering multiple different access networks. We prepared a test bed that implements a prototype system, and evaluated based on a disaster scenario.

Data backup in data center networks (DCNs) is critical to minimize the data loss under disaster. This paper considers the cost-efficient data backup for DCNs against a disaster with ε early warning time. Given geo-distributed DCNs and such a ε-time early warning disaster, we investigate the issue of how to back up the data in DCN nodes under risk to other safe DCN nodes within the ε early warning time constraint, which is significant because it is an emergency scheme for data protection against a predictable disaster and also help DCN operators to build a complete backup scheme, i.e., regular backup and emergency backup. Specifically, an Integer Linear Program (ILP)-based theoretical framework is proposed to identify the optimal selections of backup DCN nodes and data transmission paths, such that the overall data backup cost is minimized. Extensive numerical results are also provided to illustrate the proposed framework for DCN data backup.

WiFi offloading, where mobile device users (e.g., smart phone users) transmit packets through WiFi networks rather than cellular networks, is a promising solution to alleviating the heavy traffic burden of cellular networks due to data explosion. However, since WiFi networks are intermittently available, a mobile device user in WiFi offloading usually needs to wait for WiFi connection and thus experiences longer delay of packet transmission. To motivate users to participate in WiFi offloading, cellular network operators give incentives (rewards like coupons, e-coins) to users who wait for WiFi connection and transmit packets through WiFi networks. In this paper, we aim at maximizing users' rewards while meeting constraints on queue stability and energy consumption. However, we face scheduling challenges from random packet arrivals, intermittent WiFi connection and time varying wireless link states. To address these challenges, we first formulate the problem as a stochastic optimization problem. We then propose an optimal scheduling policy, named Optimal scheduling Policy under Energy Constraint (OPEC), which makes online decisions as to when to delay packet transmission to wait for WiFi connection and which wireless link (WiFi link or cellular link) to transmit packets on. OPEC automatically adapts to random packet arrivals and time varying wireless link states, not requiring a priori knowledge of packet arrival and wireless link probabilities. As verified by simulations, OPEC scheduling policy can achieve the maximum rewards while keeping queue stable and meeting energy consumption constraint.

Data center network (DCN) placement with the consideration of potential large-scale region failures is critical to ensure its functionality under such catastrophic scenarios. This paper considers the optimal DCN placement for DCN failure risk minimization against such region failures. We first apply a general probabilistic region failure model to determine the failure probability of a node/link, and then propose a general grid partition-based scheme to flexibly define the global distribution of a region failure in terms of its occurring probability and intensity. Such grid partition scheme also helps us to evaluate the vulnerability under a region failure. With the help of the vulnerability information, we further propose an Integer Linear Program-based theoretical framework to identify the optimal DCN placement to lead to the minimum DCN failure risk under a region failure. An example and extensive numerical results are also provided to illustrate the proposed framework for DCN placement.

Hybrid cloud has been considered a viable option to address the unavailability and/or limited resources of an inhouse private cloud as per user's requirements or at runtime. The approach is poised to highly benefit the user in terms of procuring the required resources and/or the time element. With many companies offering different features of public cloud services, even if such service is of the same type, the quest to discover and select the suitable public cloud service provider is of utmost importance. This paper proposed anagent-based support system to discover the most suitable public cloud service provider based on the user's requirements. Agents and ontologies were used to implement the proposed model. Verification test results demonstrates the viability and usefulness of the system.

In the actual disaster case, there is certain possibility that electric power line is damaged and power energy cannot be supplied to those communication network devices, eventually those wireless LANs cannot be functioned. Although mobile wireless network is easy to reconstruct than wired network, there may be the case that network disconnection is not affordable after disaster. That is, Disaster Information System needs a robust Never Die Network (NDN) which will be unaffected by any changes in environment after severe disaster. However, if the network is consisted with Satellite System, there are the problems of network throughput is low, cost is high and so on. In case of wireless LANs, there are the problems of physical characteristics and so on. In this paper, we introduce nobel functions for Never Die Network which consisted of Satellite System and Cognitive Wireless Network.

A major obstacle stunting the application of mobile ad hoc networks (MANETs) is the lack of a general throughput capacity theory for such networks. Available works in this area mainly focused on exploring the order sense scaling laws of throughput capacity in MANETs with omnidirectional antennas or that of static ad hoc networks with directional antennas. Although the order sense results can help us to understand the general scaling behaviors, it tells us little about the exact throughput capacity. Another limitation of available works is that the impact of transmission power constraint on the throughput capacity is largely neglected. In most MANET applications, however, the mobile nodes are usually powered by batteries and have limited transmission power. In this paper, we study the exact throughput capacity of MANETs with directional antenna and transmission power constraint, where a generalized twohop relay algorithm with limited packet redundancy is adopted for packet routing. For given transmission power constraint, we first develop a model to map the omnidirectional transmission range to that of the directional one. We then explore the exact throughput capacity under directional transmission and group-based scheduling. Finally, numerical studies are provided to demonstrate the efficiency of these models and validate our theoretical results.

We consider the secure transmission of information over Rayleigh fading wiretap channel when the main and eavesdropper channels are correlated there. Assuming that before transmission the transmitter knows the full channel state information (CSI) of both the main and eavesdropper channels, we analyze the average secrecy capacity with limited signal-to-noise ratio (SNR), for which a simple closed-form expression is derived based on the typical Marcum Q function. This is achieved by exploring the symmetry property between the main channel and eavesdropper channel to avoid a complicated integration involved in the secrecy capacity analysis, such that the secrecy capacity derivation can be significantly simplified. Numerical results are also provided to confirm our analytical ones.

This paper considers the transmission of confidential data over a quasi-static fading wiretap channel where the main and eavesdropper channels are correlated. Assuming that before transmission the transmitter knows the channel state information (CSI) of the main channel, we derive the secrecy outage probability in a closed-form expression based on a new secrecy outage probability formula, which gives a more explicit measure on the level of security compared with the previous one. Remarkably, our results, which cover the corresponding results when the main channel and eavesdropper channels are independent as special cases, reveal that channel correlation has a significant impact on secrecy outage probability and such impact can be helpful or harmful depending on the relative channel conditions and transmission SNR threshold.

About 80 percent of Japan is located in the mountain or coast sides, and so most cities should be concerned to be isolated when a ultra large disaster happens such as Japan Earthquake and Tsunami on March 11th, 2011. In fact, in the earthquake, there were many areas in the coast side of northern Japan where is isolated because of the damages, blackouts, and congestions of network information systems. In case of such a large-scale disaster, it is important to keep connectivity to avoid the isolation from other areas, and to reactivate network connections quickly within disaster areas such as between evacuation shelters and disaster headquarter. In this paper, Never Die Network consisted of cognitive wireless networks and satellite system that we have proposed is introduced, and the evaluations are held in assumptions of rural areas such as the coast cities of Iwate Prefecture where heavily disaster by Japan Earthquake and Tsunami on March 11th, 2011. The results shows that the proposed system is quickly recovered than other traditional network systems such as wired, wireless, and cognitive wireless network systems, and it is considered to be useful for the isolation by a ultra large scale disaster.

In the actual disaster case, there is a certain possibility that electric power line is damaged and power energy cannot be supplied to those communication network devices, and eventually those wireless LANs cannot be functioned. Although mobile wireless network is easy to reconstruct than wired network, there may be the case that network disconnection is not affordable after disaster. That is, Disaster Information System needs a robust Never Die Network (NDN) which will be unaffected by any changes in environment after severe disaster. Satellite Network System is one of possible solution for such a severe disaster, but it has some problems like low throughput, large latency, high cost, and so on. On the other hands, single wireless communication like IEEE802.11a/b/g also have some problems like a possible transmission distance, throughput limitation for maintaining QoS for urgent user's situations. Therefore, NDN needs to consider about additional functions for these problems of Satellite and Wireless Network System. In this paper, we introduce Satellite System for optimal transmission control method in Cognitive Wireless Network in order to consider with severe disaster. First, as our previous study, proper wireless link and route selection is held by Extend AHP and Extend AODV with Min-Max AHP value methods for optimal transmission control in Cognitive Wireless Network. Then, check-alive function, alternate data transmission function, possible alternative route suggestion, and network reconfiguration are introduced to our proposed Disaster Information Network by using Satellite System. In the simulation, ns2 are used for the computational results to the effectiveness of the suggested transmission methods in the hybrid system of cognitive wireless and satellite network system.

Japan, along with many developed countries, is facing severe social problems caused by a declining birth rate. Gradual shrinkage of the working population has brought shortages of workers performing various services such as elderly care. Women are potential workers, but social assistance of working women remains insufficient. Social services such as elderly care and support for working women must be developed to address these problems. The infrastructure for future ubiquitous services must be designed as a service platform to provide those services respecting individual personal circumstances and at socially acceptable cost. Ubiquitous services provide enhanced mobility. Future ubiquitous services will evolve toward enhanced pervasiveness, and will be defined as advanced personalized services. This report presents a new concept, Socio-familiar Personalized Service (S-P Service), for future ubiquitous services based on sociality and humanity. Moreover, we propose a scalable distributed authentication method to realize S-P Service.

IP multicasting is an efficient and scalable way to deliver high quality audio and video streams for group communication. However, widespread deployment of IP multicast is unlikely in near future and it requires substantial infrastructure modifications. For rapid deployment of multicast application, Application Layer Multicast (ALM) is an alternate choice to circumvent this situation, as it supports group communication independent of network layer support. Previous studies on ALM mainly focused on achieving high throughput for bandwidth intensive applications and unfairness of communication quality is still a serious issue in multi-source communication. In this paper, we present an autonomous distributed scheme to construct an ALM tree to improve fairness and overall communication quality among the participants in a multi-source multimedia communication. Extensive simulation and experimental results show that our proposed scheme increases the incoming bitrate of the lowest recipient among all the nodes, as well as improving fairness for all receivers.

In ubiquitous environments, there are a huge number of computer nodes which provide a lot of information services via the Internet. Therefore, a secure communication system is required for ubiquitous environments. In this paper, we propose a new architecture of distributed public key infrastructure, named as Hash-based Distributed Public Key Infrastructure (HDPKI). A HDPKI system achieves a scalable management of public key certificates by using Distributed Hash Table. Additionally, it is easy to use a HDPKI system, because we can register our public key certificates automatically. In this paper, we show scalability of HDPKI through computer simulation. According to these results, the total amount of required messages for certificate management in a HDPKI system is O(log n) where n is the number of nodes.

Sub-ontology extraction provides a solution in dealing with large ontology. As time progresses, new discoveries and new ontology emerges making the ontology data much larger. Updating the sub-extracted ontology becomes a crucial task. Updating extracted sub-ontology can be done by performing the whole extraction process repeatedly from the base ontology. In contrast, our proposed approach is to develop an incremental update mechanism which can minimize the large communication and processing overhead in the former method. In this paper, we construct and describe a grid application service framework for updating extracted sub-ontology using the incremental update mechanism. The service can be accessed through a web portal. Functional verification and analysis provides viability of the framework.

Access control to resources is one of the most important technologies for supporting human activities in the digital space. To realize control two schemes were proposed: RBAC (role-based access control) and TRBAC (temporal role-based access control) by adding time constraints and role dependencies to RBAC. However, these methods are not effective for temporal activities because of maintenance costs and inadequacy in safeness. In this paper, we focus on a flexible and secure access control in the real space, by using relations with users and situations, and propose a novel access control which is effective for temporal activities.

In this paper, we propose an advanced communication infrastructure of the agent-based middleware for ubiquitous computing environments. We focus on an adaptive communication mechanism between agent platforms, which can select a suitable communication scheme flexibly, based on properties of inter-agent communications and resource statuses. We performed some further experiments based on the results of initial experiments by using the prototype system with the proposed mechanism. From the additional results, we confirmed that the dynamic change of inter-platform communication scheme works effectively in order to realize the inter-agent communication requirements.

In the traditional network management architecture, there is an implicit assumption that a managed device will not change its location. Location related information where available is static, and it is used for simple reporting purposes. However with mobile devices these attributes are inherently dynamic. Monitoring processes of management information also encounter difficulties of network instability caused by roaming of devices or wireless signal errors. So the current approach of network management needs to be reviewed. MobileIPv6 and NEMO are standardized protocols for realizing mobility-aware network. In this article we propose new network management technologies for MobileIPv6/NEMO network based on the Internet standard network management protocol, simple network management protocol (SNMP). Our focus is the importance of 1) location awareness and 2) intelligent monitoring process. We explained about the MobileIPv6/NEMO-MIB that is aware of mobile devicepsilas dynamically changing location. We also propose the delayed data sending method that realizes effective transfer of management information without congestion over an instable network. From an evaluation in simulations, and experiments in real environment, we confirmed that our approach is effective for improving monitoring processes for mobile devices in management of MobileIPv6/NEMO network. This is one of the first management applications that are completely based on Internet standard protocols of MobileIPv6/NEMO, and SNMP.

In ubiquitous computing environments, quality of service (QoS) in overall system may be affected when context information with excessive or deficient quality/quantity is exchanged among various entities in the environments.In this paper, we propose an adaptive control scheme of context information delivery for ubiquitous services based on QoS and quality of context information (QoC). To achieve the advanced control, we compose each entity as highly autonomous and cooperative agents. The system with this scheme can adapt to a variety of real-world environments and is able to maintain user requirements for QoS.This paper especially focuses on the design and implementation of the proposed scheme. We also illustrate the effectiveness of our scheme with some initial experiments from a viewpoint of adaptability for the changes which occur in entities in real world.

The semantic grid as the uniting concept of semantic web and grid computing, and its ontology technology provide an efficient data retrieval methodology in widely distributed semantic grid resources over the Internet. As the number of semantic grid resources increase, e.g., ontology servers, the amount of data increases and managing job workflows is becoming increasingly complex. This paper proposed a validation framework for sub-ontology extraction workflows in our proposed semantic grid computing environment. We considered two ontology optimization schemes and design its workflow models using Petri Net. The workflow for each model is described and validated. The results justify the feasibilities of our proposed validation framework of the aforementioned models which can be used as building blocks to model large and efficient sub-ontology extraction workflows in a semantic grid.

Wireless network is an essential and integral part of the ubiquitous environment. For efficient access control, two different transmission schemes are used: The basic carrier sensing multiple access with collision avoidance (CSMA/CA) and request-to-send/ clear-to-send (RTS/CTS) handshaking. The RTS/CTS handshaking addresses the hidden terminal problem as well as reduces the chance of collision in case of higher node density and traffic. However, in networks with low density, basic scheme would lead to higher throughput due to its less overhead. Efficient switching between these two schemes is imperative to maximize the throughput. We have first investigated to find a meaningful threshold value according to the network situation. The proposed algorithm then dynamically adjusts RTS Threshold according to the packet delivery ratio, which is an indicator of network traffic and shows a significant improvement over existing CSMA/CA and RTS/CTS schemes. Our adaptive scheme performed even better when data rates increases. We verify our proposed scheme with extensive network simulation using ns-2.

We propose a supervisory system that deals with actual situations and social aspects of users in ubiquitous computing environment in this paper. To realize a gentle and safe supervision, we have to consider social relationships between observers and the watched person to give adequate level of privacy to the services. We propose "uEyes", a ubiquitous supervisory system that introduces a new feature for the supervision, i.e., social context awareness. By using this feature, environmental information acquired from real world and knowledge on social activities of people are integrated effectively. From experimental results using a prototype of uEyes for supervising elderly people, we show that the social context awareness, as well as other components of the system, effectively works to support the supervision.

A new 3-D virtual environment (3DVE) system named "QuViE/P" has been proposed in this paper, which can greatly enhance the quality of service (QoS) that users actually feel as good as possible, when the resources for computers and networks are limited. To do this, therefore, we focus on characteristics of the user's perceptual quality evaluation on 3-D objects. In this paper, we propose an effective QoS control scheme that introduces a relationship between system's internal quality parameters and user's perceptual quality parameters. This scheme can appropriately maintain quality and functions for users and is expected to drastically improve convenience when using 3DVE under the situation that resources are limited. Experimental results obtained from using a prototype of QuViE/P show effectiveness of our scheme as follows: Even when computer resource is reduced to 30% of the required amount, our proposed scheme can preferentially keep quality of important objects. Moreover it continues to provide quality and functions that user requires. Whereas in traditional QoS control scheme, objects of importance disappeared in similar situation.

In this paper, we propose a log summarizing method to help a network manager to recognize and handle a network event. Our method can accurately extract only necessary information in real-time by stepwise information extraction technique. This feature can help the network manager to handle an event quickly with less management burden. With our experimental results, we show that our method has the ability to remove more than 60% - 90% unnecessary records, without losing any necessary information. Additionally, our method can process a log containing massive records in real-time.

As the Internet Protocol (IP) does not ensure the authenticity of packets, it is sometimes necessary to discover or to confirm the real source of a packet received from the Internet. Examples of these situations include tracking down the host from which an attack was launched. In this work we propose a new architecture for IPPT (IP Packet Tracing) based on the traditional concept of keeping traffic logs stored in Bloom filters. The proposed architecture returns an attack graph that precisely identifies the route traversed by a given packet allowing the correct identification of the attacker. We show that previously published approaches may return misleading attack graphs in some particular situations, which may even avoid the determination of the real attacker. The proposed architecture has two other features that improve the efficiency of the returned attack graph: separate logs are kept for each router interface improving the distributed search procedure; an efficient dynamic log paging strategy is proposed. The communication among the system's components preserves the confidentiality of the packet's information. The architecture was implemented and experimental results are presented.

In this paper, we present an enhanced adaptive frequency hopping (EAFH) mechanism for improving the performance of frequency hopping-based wireless personal area networks (WPANs) under frequency-static and frequency-dynamic interference. The proposed mechanism monitors the overall packet error rate (PER) of the system to determine the right number of channels to be excluded from the hopset. Then based on the PER of individual channel, it decides whether to exclude a certain channel or not. Finally, proper packet length is associated with those channels remaining in the hopset. These decisions, which pertain to hopset size and packet length, are made so as to optimize the performance of the hopping system in a coexistence environment. We developed an analytical model to justify the behavior and performance of the proposed mechanism. Simulations are conducted under an environment of some collocated Bluetooth (BT) piconets and a Wi-Fi network to validate the developed model and show the superiority of EAFH. Simulation results show that, compared with those existing mechanisms including orthogonal hopset-based mechanisms, EAFH could provide much higher throughput while still maintaining reasonably good channel occupancy.

For effective management it is necessary to have methods by which management applications can periodically retrieve large volumes of information from network devices. In this work we examine the issues related to standardsbased bulk-information retrieval and then propose a technique that extends the limits of periodic bulk-retrieval. The impact of the technique is demonstrated using a prototype implementation with special emphasis on network monitoring, traffic management and security management by comparing with the widely used RMON technology. We then discuss the problems of monitoring in a mobile environment in the context of the newly defined IETF standards track mobile IPv6 management information base (MIPv6MIB) and show how the bulk retrieval technique can be used to provide a mechanism for reliable monitoring in a mobile environment.

We have been working on research and development of advanced network and applications called "flexible computing". We are now in the next stage of this research, strongly pressing forward the concept of flexible computing, namely, "symbiotic computing", towards next generation computing model based on co-existence of real space and digital space. In this paper, we explain basic concepts, architecture and enabling technologies of symbiotic computing that we are aiming to develop.

In Bluetooth network environment, device discovery is achieved by the master running the Inquiry protocol and slaves running the Inquiry Scan protocol. The master and a slave establish a connection using the Page and Page Scan protocols, respectively. Once a connection is established between a master and a slave, upper level data can be exchanged between the two devices. Thus, device discovery and connection establishment are fundamental to communication between two Bluetooth devices. While a device is in the process of discovering other devices, there is a random delay. We analyze the discovery time for different situations. We further show the delay-distribution for varied number of devices. We explain reasons of occasional long discovery time, and propose means to improve it.

We introduce an inheritance concept into a specification method of mobile and real-time systems in order to reuse and refine existing specifications. Reusability by inheritance is emphasized in this paper. We take multiple inheritance to enable to reuse several specifications at a time. An upper specification can be skillfully divided into inherited parts and non-inherited ones. Therefore, a necessary part of the specification can be reused for a lower specification. As an application, the FIPA contract net interaction protocol is specified incrementally by using our method. We have been developing support tools for specifications described using our proposed method.

In this paper, we propose an agent-based mobile ad-hoc service construction system named AMACS, which is an agent based middleware and improves usability of user communication on ad-hoc networks. AMACS exchanges user information among computers and makes users possible to use various communication services by only selecting target user's name and service name. In this paper, we describe agent-oriented service composition method of AMACS, and show detailed design and implementation. Finally, through experiments using prototype system, we show effectiveness of AMACS.

Effective information services could be provided for users by investing meta-data in information sources and making software agents understand it. In this paper, we make better use of a collection (ontology) of meta-data in the semantic Web technology for the design of an e-learning system that enables to provide learners with a more effective education support. The learning domain is cryptography in network security. We define various concepts in the cryptographic domain and the relations among them as the ontology, and propose a way of utilizing it in the learning process. The strength of our ontology-based e-learning system is demonstrated through application examples of the prototype system that we have been developing.

In a Bluetooth piconet, the Master essentially controls the channel. Due to an absence of coordination between independent Masters while accessing the wireless medium, devices will encounter high packet interference if several piconets are simultaneously operating in the same area. Since even a headset and a mobile phone can be connected with a Bluetooth link forming a piconet, it may not be unusual to find tens of independent piconets in crowded places like airports, international conferences, shopping malls, and so on. Study of packet interference is important because interference affects the throughput of a piconet. Motivated by the fact that applications will benefit, in terms of higher available data rate in one direction, by using multiple-slot packets in an asymmetric manner, in this paper, we present an analytical model of packet interference in a cluster of piconets using multiple-slot packets. Also, considering that all the portable devices can have a Bluetooth interface and people are highly mobile these days, it will not be uncommon to find a cluster of piconets of both the 79-hop and the 23-hop types in the same area. We then present an analytical model of interference of multiple-slot packets in a heterogeneous cluster of Bluetooth piconets. By a heterogeneous cluster we mean some piconets are of the 23-hop type and the rest are of 79-hop type. We show how the aggregate throughput in a cluster of piconets degrade under various traffic scenarios, such as 1-slot, 3-slot, and 5-slot packets in symmetric and asymmetric modes in synchronous and asynchronous conditions of Master clocks. Our analytic model is based on the idea of probabilistic graphs, where a node denotes a piconet and an edge denotes the probability of interference between two nodes. Though the 23-hop system has been phased out, our work gives a general approach to model packet interference in multiple, frequency-hopping systems that need not be Bluetooth systems.

In multiagent system, it is important for agents to assess the situation prevailing in the system, especially to anticipate other agents' intentions. We argue in favor of cooperation among agents and propose a new method to utilize potential field as a tool for estimation of the environment. In our method, potential of environment gives agents some criteria to assess environmental situations from their own perspective. The potential of each object represents its influence on the environment and the environmental potential, i.e., summation of each object's potential, represents global situation of the environment. Agents' decision of their behavior will be done by refining the policy obtained from potential. We use a trash collecting problem as an example to show the effectiveness of our method. Furthermore, we show the efficiency of our method by some sets of experiments of the trash collecting problem. We also discuss the applicability of our method to hybrid systems, environments where available information has a margin of error, or environments where agents' range of vision are limited.

Generally, the 3D-virtual space applications need powerful image processing capability of computer platform and broadband network environment. Therefore, user must perform appropriate setting of the system to receive the service from the virtual space with comfortable QoS, under the circumstances when computer and network resource are changing in almost every moment. This research is aiming for the improvement in convenience of user of 3D-virtual space system by automatic QoS control mechanism. We propose a design and implementation of 3D-virtual space with QoS awareness based on multiagent framework.

Study of packet interference is important because interference affects the throughput of a piconet. Motivated by the fact that applications will benefit, in terms of higher available data rate in one direction, by using multiple-slot packets in an asymmetric manner, in this paper, we present an analytical model of packet interference in a cluster of piconets using multiple-slot packets. Also, considering that all the portable devices can have a Bluetooth interface and people are highly mobile these days, it will not be uncommon to find a cluster of piconets of both the 79-hop and the 23-hop types in the same area. We then present an analytical model of interference of multiple-slot packets in a heterogeneous cluster of Bluetooth piconets. By a heterogeneous cluster we mean some piconets are of the 23-hop type and the rest are of 79-hop type. We show how the aggregate throughput in a cluster of piconets degrade under various traffic scenarios, such as 1-slot, 3-slot, and 5-slot packets in symmetric and asymmetric modes in synchronous and asynchronous conditions of master clocks. Our analytic model is based on the idea of probabilistic graphs, where a node denotes a piconet and an edge denotes the probability of interference between two nodes.

In most of the research for the wavelength allocation in wavelength division multiplexing (WDM) networks, the connection setting delay time is not considered. However, the entire bandwidth increases because of an increase in the transmission capacity of one wavelength. Therefore, the connection setting delay time should be considered because the data transmission time is shortened relatively. In this paper we propose a new connection setting method considering connection setting delay. The performance evaluation via simulations shows that the proposed method has better performance than the conventional forward and backward reservation methods.

We describe an agent-based design of multimedia processing software component in the Flexible Network Layer (FNL). In FNL, Middleware Service Unit (MSU) provides multimedia communication services for applications by combination of components for processing various multimedia data. In MSU, it is required to construct/reconstruct the necessary and sufficient functions of multimedia data processing dynamically, considering the QoS, user requirements, resource statuses, and characteristics of the media data. In this paper we propose an architecture of a Media Element Agent (MEA) to fulfill the requirement. The MEA consists of multimedia processing component and knowledge of designer developer and user of the component. We also show a scheme of multiagent-based construction of MSU with organized behavior of the agents.

We have proposed an application-oriented flow control system which decides the priority of flow according to the application utilizing situation and controls application flow. We have observed some problems at the time of experimentation using the prototype system. In this paper to improve the maintainability and availability of our proposed system by solving the problems, we propose two improving methods. We have carried out an evaluation through experiments, and the results show the effectiveness of our proposal.

The main subject of this study is to inquire whether it is possible to control transient dynamics in a multiagent dynamical system. It is a well known fact that any multiagent dynamical system follows its transient dynamics, whether its transient dynamics are temporal or not, whenever a dynamical system starts operating at any initial condition. Especially in the case of a transient state occurring frequently due to intermittent perturbations, such as from user's requests, most tasks would be processed on the system's transient dynamics. Then undoubtedly you would care to ask "Is it possible to control transient dynamics on performance and life span, or not?" So far however, for transient dynamics being rated as temporal and uncontrollable dynamics, any systematic knowledge on controlling transient dynamics for multiagent dynamical systems has not been clarified. This study has introduced a new type of agent strategy called "info-reliability." It has clarified the diversification of agent strategy as an available procedure to make the system's transient dynamics controllable on its performance and on the life span of the transient dynamics.

We present a design and implementation of a flexible videoconference system (VCS) using multiagent computing technology. The proposed system, we named FVCS, aims to reduce the burden of the users under the operational environment with insufficient computational resources, such as the Internet environment with small-scale computers at homes and offices, by embedding flexibility to the conventional videoconference system. In this paper, we design and implement FVCS with knowledge-based multiagent framework to realize adaptability of FVCS. We also evaluate the adaptability of the prototype systems of FVCS based on an operational situation observed in its experiments. From the result of the experiments, we conclude that the multiagent-based design and implementation is reasonable for construction of FVCS.

In order to support multimedia communication over high speed networks, it is necessary to develop routing algorithms which use for routing more than one QoS parameter. This is because new services such as video on demand and remote meeting systems require better QoS. However, the problem of QoS routing is difficult and to find a feasible route with two independent path constraints is NP-complete. Therefore, QoS routing algorithms for high speed networks must be adaptive, flexible, and intelligent for efficient network management. In a previous work, we proposed a genetic algorithm (GA) based routing method. This method used only the delay time as a routing parameter. In this paper we improve the previous work in three aspects. The new QoS routing method uses two QoS parameters for routing. We implemented a new tree generating algorithm which generates and reduces the tree automatically. Furthermore, we carried out the simulations for different kinds of networks. The simulation results show that the proposed method has a better performance than a conventional GA based routing algorithm.

Proposes a flexible multimedia system (FMS) which is based on an agent-oriented architecture. The system is able to organize the required functions itself, and to provide both real-time and stored multimedia information services simultaneously to users, even though various users' multimedia environments and the resource utility of the computers or networks have been dynamically changed. This distributed multimedia system not only integrates various multimedia information distributed over computer networks but it also provides that information to the users in accordance with their requirements during real-time multimedia communication which must guarantee the user-requested quality of service (QoS), even though the computer and network resources may change statically or dynamically. This paper describes the FMS architecture for a multimedia teleconferencing service with adaptive QoS-guarantee functions, and designs the FMS so as to implement a prototype system. In this teleconferencing service, the FMS is able to realize one of the multimedia communication services flexibly for service requests and QoS requests from users.

Since network resources are usually limited, the ability to carry out resource reservation in advance, as well as efficient dynamic multicasting when destination nodes can join and leave the group during the communication period, are essential in all distributed multi-party applications. Total or partial re-routing of a multicast tree for dynamic multicast groups can optimize the tree cost to some extent but they are complex. Furthermore, optimal multicast routing has been proved to be an NP-complete problem. In this paper, we propose an efficient dynamic multicast routing algorithm, which optimizes the total cost of the Steiner tree over the whole session period in an advance resource reservation environment, where information about the resource reservation (i.e. leaving times of participants at the time of joining) are available. The efficiency of our algorithm compared to other existing algorithms is shown by various simulation results.

We propose a formal method to maintain mobile systems placed on fluidal ambiences using a process calculus in this paper. Behavior of physically movable entities of mobile systems, e.g. mobile telephone systems and intelligent transport systems (ITSs), may be affected by their surrounding. We have focused on effects of ambiences to behavior of mobile systems and have introduced the notion of a field into a concurrent calculus /spl pi/F, an extension of /spl pi/-calculus, formalizes processes constrained by ambiences. Based on /spl pi/F, our maintenance method indicates us how an ambience should be recovered when it is damaged.

IMI provides a scalable and flexible measurement infrastructure. It essentially uses RMON-type passive monitoring and on demand, active probes. It is built on the SNMP framework: so all interactions are through MIB-variables; security and access control is in place. Detecting congestion is a challenge and diagnosing it is an even greater challenge. In this work we have experimented with techniques of detecting congestion in the network using the distributed infrastructure of IMI. As a symptom of congestion, retransmission packets in the network traffic are detected, counted and analysed. The related information from various IMId's (IMI-daemons) are collated and used in conjunction with configuration information to detect and then locate a congestion bottleneck.

In this paper, the authors propose a decomposition method for a formal specification that divides the specification into two subspecifications composed by a parallel operator. To make these specification behaviors equivalent before and after decomposition, the method automatically synthesizes an additional control specification, which contains the synchronization information of the decomposed subspecifications. The authors prove that a parallel composition of the decomposed subspecifications synchronized with the control specification is strongly equivalent with the original (monolithic) specification. The authors also write formal specifications of the OSI application layer's association-control service and decompose it using their method as an example of decomposition of a practical specification. Their decomposition method can be applied to top-down system development based on stepwise refinement.

As corporations continue to introduce workflow systems, different systems have appeared for processing of core-business tasks for information processing and clerical work. A number of different models for coordination of different workflow systems have been proposed; but workflows for core-business tasks constitute the central business processes of the company, and certain aspects of coordination of such workflows differ from other kinds of coordination. This paper clarifies these differences, and proposes a model for coordination, which takes these differences into consideration. In addition the application of this model to an actual system and confirmation of its effectiveness are also reported.

Asynchronous messaging systems like e-mail systems need some advanced characteristics, such as intelligence, controllability and scalability, to accomplish more effective and sophisticated message handling. We propose a framework of next generation messaging systems, Flexible Asynchronous Messaging System (FAMES), which consists of autonomous and collaborative software agents. In FAMES, various messaging functions composing of agents can be utilized to integrate heterogeneous user environment. Moreover, FAMES operates message flow in an intelligent manner, considering the receiver's own convenience and that flexible message delivery can be achieved. We designed and implemented the proposed system based on multi agent technology, and we show its effectiveness through experimental studies using a prototype system.

Routing with multiple QoS constraints is known to be a NP-complete problem. In our previous work (QoSR/sub BF/ algorithm), we have shown that, for a number of specific QoS constraints, this problem can be solved in polynomial time, when a weighted fair queueing (WFQ) service discipline is employed. QoSR/sub BF/ is an on-demand algorithm. We propose a number of QoS routing algorithms for pre-computed paths, when all or some of the flow specification parameters and the amount of bandwidth that has to be reserved are not known a priori. We also show that the size of the routing table could be reduced, as paths satisfying some conditions could be neglected.

In this paper we study QoS based routing algorithm for supporting resource reservation in high-speed Integrated Services Packet Network (ISPN). Recently, this problem was proved to be NP-complete. However, when the considered QoS constraints are bandwidth, delay, delay jitter, and loss free, we have shown that by employing Weighted Fair Queueing (WFQ) service discipline, the complexity of the problem could be reduced to that of shortest path routing without any QoS constraints. Then such a multiple QoS constrained route could be searched in polynomial time. We also present the routing algorithm (called "QoSR/sub BF/"), which is a modified version of Bellman-Ford shortest path algorithm. Simulation results show that QoSR/sub BF/ has better performance compared to the existing QoS routing algorithms.

In existing meeting scheduling systems, finding a common free time slot of all (prospective) participants is the goal. When such a free-time slot is not found, the host has to ask the busy participants to change their schedules. Changing a schedule is a complex process requiring a lot of negotiations and, there is no guarantee that the goal will be achieved. In the worst case the host has to ignore the time slot (which was probably the first choice) and try to schedule the meeting in another time slot (probably a lesser choice). The process will continue till the scheduling succeeds. We argue that it is not always necessary for all the participants to attend a meeting. There are some participants whose presence is mandatory for the meeting. The presence of other participants are non-mandatory. The meeting can proceed in the absence of some of the non-mandatory participants. This allows greater flexibility and more efficient scheduling. This paper introduces the concept of a Quorum in the meeting scheduling process and proposes a two-round negotiating protocol to find the time-slot which meets the quorum requirements. To establish the robustness of our scheduler, we simulated scheduling in our lab, and showed its flexibility in scheduling a meeting.

LOTOS formal description technique (FDT) is applied to the formal description of distributed systems and the specification of OSI protocol layers. LOTOS is difficult to understand and to learn because it is based on a mathematical model. In this paper, for supporting the knowledge acquisition of learners studying basic LOTOS, we suggest a new algorithm that can verify an equivalence relation, find an error location, and correct an error when the error occurs at another process. Finally, we give an example of a prototype program for an educational support system for basic LOTOS.

Summary form only given, as follows. In this talk, Dr. Hwang will present two approaches to scalable parallel computing: The first approach is based on scaling STAP benchmarks on Cray T3D, IBM SP2, and Intel Paragon. STAP was originally developed by the MIT Lincoln Laboratory for real-time signal processing. The benchmark suite was recently parallelized and tested on several available MPPs (massively parallel processors). The second approach is to develop an SSI (Single-System-Image) cluster of UNIX workstations and SMP servers for distributed multimedia and Intranet applications. The talk will evaluate scalable multiprocessors and network-based cluster architectures. Specific R/D topics to be covered include the following: - STAP benchmark evaluation of T3D, SP2, Paragon, and Power Challenge/XL - Architectural - Hardware and software support for SSI in a cluster of workstations and servers. - Distributed cluster computing in multimedia and Intranet applications. assessment of recent advances in CC-NUMA and Clusters. Scalable parallel computer platforms provide not only an incremental growth path, but also performance scaling and enhanced availability. These features are very much desired in today's business and scientific applications. Dr. Hwang will share the research findings and benchmarking experiences from his research groups at USC and HKU. He will also comment on the research, development, and application trends in parallel and cluster computing.

Communicating entities in a protocol specification communicate with each other and provide services to their users. Once the behaviours of the entities (specification of the protocol) are specified they are not changed. The entities provide a fixed set of services to their users. However, different users have different requirements and their requirements change often. The requirement changes in general are small in terms of the size of the behaviour expressions of the entities. Traditional protocol synthesis techniques have given considerable attention in construction of new protocols for fixed set of services but less attention to the attractive maintenance issue of protocol to adopt new protocol requirement changes. What is desirable is a protocol synthesis method which adopts new protocol requirement changes into the behaviours of entities or protocol specifications. In this paper, we propose a protocol synthesis method which adopts the new protocol requirement changes into the protocol specification. In this way, we can use existing protocol specifications and maintain them to adopt requirement changes. We use the formal specification language LOTOS to specify requirement changes and the behaviours of entities.

Much research efforts are presently involved in developing network protocols suitable for multimedia services through LAN and even Internet. Due to large size and time sensitiveness of data, it is usually a hard task to deliver the services up to the expectations of the users. But the basic intention of the user, for the multimedia services, usually have a wide scope for tolerance and flexibility. If that flexibility is explored and exploited, it is possible to basically satisfy the user even with marginal resources. It is important to intelligently interpret user's request as well as distribute the system and network resources optimally. In this paper we are proposing an Intelligent Soft Resource Reservation Protocol (ISORRP) for realizing acceptable running quality of application by intelligent interpretation of users' requests and optimum distribution of available resources among them. In this architecture QoS to a session is only flexibly guaranteed but always to a level acceptable to the user.

First-order multiparty interactions, a generation of multiparty synchronization, are a powerful communication mechanism that allows a set of processes to enroll into different roles of an interaction and to execute the interaction in a synchronous way, and guarantees conflict interactions to be executed exclusively. It is not a trivial problem to implement first-order multiparty interactions in a network environment. The implementation has to maintain the synchronous and exclusive properties mentioned above, be fair and make progress. In this paper, we propose a new distributed algorithm for implementing first-order multiparty interactions based on a new implementation model, in which a role manager is devised for each role. Our algorithm solves the problem with O(|R|/sup 2/.|P|) messages per interaction as opposed to |P|/sup 2/ messages required in Joung and Smolka (1994), where |R| is the number of roles of the interaction and |P| is the number of processes. Our algorithm is more efficient than that in Joung and Smolka, when |R|/sup 2/<|P|. Furthermore our algorithm is closer to the fully distributed one in the sense that (1) every process (role manager) only knows its adjacent role managers (processes), and (2) the time complexity of local computation in each process and role manager is equal.

The problem of modifying an existing protocol specification of a communicating system in Labelled Transition System (LTS) based on changes of it's service specification in LTS is discussed. Two types of changes of a service specification are treated: addition of a behaviour expression to the service specification and deletion of some parts of the behaviour expression from the service specification. For each change, a modification method is proposed and a property of the method is shown. From the point of view of verification and validation of a specification, it is desirable to separate a changed part of the specification from the existing specification. Thus, especially for the former type of changes that is addition of a behaviour expression to the service specification, the method to express changes of the service specification by using a concurrent LTS is proposed. The method proposed in this paper is efficient and desirable when the size of the changed part of the service specification is small in terms of behaviour expressions.

The core of the problem of Information Gathering is how to generate a concise, high-quality response to the information needs of a user. However, this task is becoming difficult due to the explosion in the amount of electronic information. Agent-based solutions have become an popular approach for locating information in an growing distributed heterogeneous environment like Internet. We first survey the existing non-agent and partially agent-based solutions; then to overcome their drawbacks we propose a completely agent-based solutions, when the different types of agents introduced-named user agent, machine agent, manager-cooperate to decrease user load and gain efficiency in the retrieval process.

In order to achieve a more convenient and intelligent handling of LOTOS specifications, an approach is proposed wherein specifications are translated into an appropriate equational logic language and interpreted. LOTOS has an excellent formal model for describing communication processes and equational logic languages have the capability of inferencing and data abstraction. Naturally, the marriage of LOTOS and equational logic provides a powerful framework with features that could not be realized in existing technologies. To demonstrate this potential, AMLOG is chosen as the appropriate equational logic language. Apart from rapid prototyping of specifications, some of the exciting possibilities of the new framework that are demonstrated include stepwise refinement and testing for correctness of specifications, facilities for property checking and verification of bisimulation equivalences. Also, the derivation of behavior expressions from trace histories is shown. The approach, extensible to other FDTs as well, is a step towards realizing an intelligent communication protocol specification environment.

Entities in communication systems behave under sets of communication rules (protocols) and their behaviours are related to each other. Using this relationship, we present a synthesis algorithm to derive a structured protocol model by generating a peer entity from a given entity automatically. The given entity is in the form of a communicating process, which is natural in the context of communication protocols. We prove that the synthesized protocol model consisting of the generated entity and the peer entity is safe: i.e. logical errors free, collectively represented as deadlock free and is bisimulated by both entities. Unlike many previous works, where FSMs (Finite State Machines) are used to synthesize protocol model we present our synthesis algorithm for the process-algebraic language LOTOS, which is one of the FDTs developed by ISO.

Proposes a completely agent-based approach for information gathering on information networks with a large number of distributed heterogeneous sources, such as Internet. Locating and accessing information in such a large distributed system which changes dynamically is challenging. An agent-based solution is the most suitable in such situations. We first review the drawbacks of existing non-agent and partially agent-based solutions for locating information on Internet. We introduce a CAS model to express a Society of Cooperative Agents and then explain how our completely agent based solution based on the proposed CAS model overcomes the weak points of existing approaches.

Real-time communication networks are designed mainly to support multimedia applications, especially the interactive ones, which require a guarantee of Quality of Service (QoS). Moreover, multicasting is needed as there are usually more than two peers who communicate together using multimedia applications. As for the routing, the network has to find an optimum (least cost) multicast route, that has enough resources to provide or guarantee the required QoS. This problem is called QoS constrained multicast routing and was proved to be an NP-complete problem. In contrast to the existing heuristic approaches, in this paper we propose a modified version of a Hopfield neural network model to solve QoS (delay) constrained multicast routing. By the massive parallel computation of neural networks, it can find a near optimal multicast route very fast, when implemented in hardware. Simulation results show that the proposed model has performance near to the optimal solution and comparable to existing heuristics.

The reuse of existing software is one of the most effective ways for software development. We have focused on the specification process with FDTs (Formal Description Techniques), and have proposed a new concept of similarity based on LTSs (Labelled Transition Systems) as a criterion to reuse specifications. However, it's definition has some problems, such that (a) it can't be applied to an LTS with some loops, and (b) the definition of similarity between actions is not clearly expressed. In this paper, we remove these problems in order for our approach to be widely applicable. For the first problem, we extend the definition of similarity to be able to apply to an LTSs with some loops. For the second one, we consider that the similarity of actions is defined based on not only the name of actions, but also the attribute of actions and the way of occurrence of actions as the temporal ordering.

We consider an extended committee coordination problem in an autonomous decentralized social environment. The basic committee coordination problem and a distributed algorithm, as a solution to this problem in a distributed environment, are presented by K.M. Chandy and J. Misra (1988). The algorithm guarantees the synchronous and exclusion properties of the problem and is fair (i.e. starvation-free) and makes progress (i.e. deadlock-free). In an autonomous decentralized social environment, besides the above mentioned properties, some social properties, such as individual preference, privacy protection, and stable assignment, are required to be considered and guaranteed. We extend the committee coordination problem by introducing some social properties, such as individual preference and stable assignment and give a decentralized social algorithm as a solution to this extended problem. The algorithm guarantees not only the synchronous and exclusion properties but also individual preference and stable assignment properties.>

A concept of a flexible network is formalized as a foundation of next generation distributed systems. Considering the requisite properties of flexible networks, we propose an architecture of a flexible network called agent oriented flexible information network (AFIN) model. The model is based on the multi agent paradigm. Furthermore, we focus on a communication network which is a core component of the flexible information network. We propose an agent oriented flexible communication network (AFCN) model and demonstrate with an example the advantages of the proposed architecture of the flexible network.>

There has been an effort towards developing a specification language for describing processes. To this end, Formal Description Techniques (FDTs) have been proposed. FDTs in general fare well in describing a target system unambiguously, precisely, and completely. However, the drawback of these FDTs are that they are generally not user-friendly (easy to read) and are difficult to write. These drawbacks could be overcome by a new technique of automatic synthesis of formal specifications from user requirements. A state transition system is an underling structure for formal description techniques and used as a formal specification itself. In this paper, we propose an automatic transformation from user requirements into formal specification represented as state transition systems and its connection with partial logical Petri nets.

To flexibly develop services on communication systems, support for specification description is more important than others in development processes. We have developed a specification description language HSC for communication systems. In this paper, we propose a new design method, and its support environment. The method and system effectively utilize the features of HSC and also apply the CBR technique for reusing service specifications being developed. We have experimented with service specifications of communication systems by using this system. Through these experiments, the effectiveness of this method and its support environment is ensured.

No abstract available.

As a fundamental study of multiple image processing, the authors have developed a new technique for the analysis of multispectral remote sensing data. Though the basis of the authors' algorithm is similar to a histogram analysis, they have proposed a novel way of the representation of multidimensional image data, which facilitates a nonexpert to locate and assign different classes present in the data set. The authors' experimentation was done with NOAA satellite image data. The brightness of the received data from channels of different frequency bands are the different dimensions of the multispectral image. By using this method, the authors could successfully classify NOAA satellite data received from the northern part of Japan, and locate the plane areas as an exercise. The authors have quantitatively compared their result with official data. The authors' result was found to be only 1 percent in deviation with the official data.>

An algorithm for transforming LOTOS specifications from monolithic style to constraint-oriented style is proposed. The objective of this transformation is to decompose monolithic LOTOS behavior into two processes composed by the parallel operator. In order to make the behaviors observed congruent before and after the decomposition, the algorithm creates an additional process from the given specification and adds to the decomposed processes using a parallel operator. The additional process consists of n interleaved subprocesses (n /spl ges/ 1). There are no internal interaction gates between decomposed processes and the added process. The interactions among them occur only at the visible gates. This transformation has the following applications: (1) modularization or decomposition of a specification, (2) restructuring of complex specifications, and (3) derivation of protocol specifications from service specifications.>

An attempt is made to design a user-friendly software environment for protocol synthesis based on the FSM (finite state machine), and to show the validity of applying AI (artificial intelligence) techniques to the construction of such a system. For that purpose, the authors have first designed a user-friendly software environment, named SEPS, using the programming language C, which belongs to the procedural programming paradigm. The aim of SEPS is to help a protocol designer to easily design a protocol and avoid logical errors like unspecified receptions and state deadlocks. In order to enhance the productivity of protocol development, a user-friendly interface has been designed which employs the multiwindow mechanism and provides the graphic tools in this system. Consequently, a protocol designer without any experience in protocol synthesis can easily design a protocol without logical errors. The authors have also designed a knowledge-based software environment for protocol synthesis, named KSPS, using the expert system tool OPS83. KSPS has the same functions as SEPS. The advantages of KSPS over SEPS in terms of extension, modification, and maintenance of protocol development systems are shown.>

A knowledge-based design methodology for computer communication systems is proposed, along with a framework for a knowledge-based design support system. The design methodology is based on the user-requirements-oriented approach parameters. According to these requirements, formal specifications are defined as user's view virtual machine (UVM) and designer's view virtual machine (DVM). These virtual machines are constructed as knowledge models from the specifications. Due to the design methodology, a knowledge-based design support system for computer communication systems, called KDSS, is constructed. This design support system consists of many expert systems corresponding to the design phases given by methodology. A design example is given to illustrate the methodology.>

An intelligent support system, designed to make the development of protocols and communication software easy and user-friendly, is described. The support system is outlined and its accessories (the knowledge-based specification editor, the validation expert system, the software generation expert system, the conformance-testing expert system, and the protocol-conversion expert system) are described in detail. Artificial intelligence techniques are used in the design of each component of the support system. An example which demonstrates the functions of each component in the support system is given.>

A knowledge-based system for protocol synthesis named KSPS is presented. The aim of KSPS is to help the protocol designer design a protocol without logical errors, such as unspecified receptions and state deadlocks. KSPS consists of three major components: a knowledge base, a user interface, and an inference engine. The construction of the knowledge base and the user interface is examined. The knowledge of protocol synthesis represented in the production model and in the procedure programming model is embedded in the knowledge base. A user-friendly interface with a multiwindow mechanism is designed which provides the graphic tools in this system. Consequently, the protocol designer without experience in protocol synthesis can easily design a protocol without logical errors.>

An interactive synthesis algorithm, to construct two communicating finite-state machines (protocols), is presented. The machines exchange messages over two unidirectional FIFI (first-in first-out) channels when the function of the protocol has been given. The synthesis algorithm first constructs the global state transition graph (GSTG) of a protocol to be synthesized and then produces the protocol. It is based on a set of production rules and a set of deadlock avoidance rules, which guarantee that complete reception and deadlock freeness capabilities are provided in the interacting process. This synthesis algorithm prevents a designer from creating unspecified reception and nonexecutable transition, avoids the occurrence of deadlocks, and monitors for the presence of buffer overflow.>