Devices DC, RF, and microwave power performances between Al0.3Ga0.7As/In0.15Ga0.85As double doped-channel FET (D-DCFETs), conventional doped-channel FETs (DCFETs) and HEMTs are compared with each other. Device linearity and power performance have been improved by a double doped-channel design. The D-DCFETs provides a higher current density, higher gate breakdown voltage, and improves gate operation bias range as well as frequency performance. The linear power gain and output power for D-DCFETs is 19 dB and 305 mW/mm with a power-added efficiency of 52% at Vds = 2.5 V under a 1.9 GHz operation. These advantages suggest that double doped-channel design is more suitable for a high linearity and high microwave power device applications.

System needs of growing systems including heterogeneous functions and operations are increased. High assurance system that achieves high reliability and high availability is very important for such systems. In order to realize high assurance system, we developed the assurance technology based on ADS (Autonomous Decentralized System). When a growing system changes or grows, its reliability may be lowered. In this paper, we clarify the risk factors which lower the reliability and quality of a growing system when the system is modified. We will then examine the technology to eliminate or mitigate those risk factors, and propose adaptive assurance technology that can minimize the risk. We also applied this technology to ATOS for Tokyo Metropolitan Railway Network as an example of really changing and growing system and mention its effectiveness. ATOS; Autonomous Decentralized Transport Operation Control System.

Decentralized XML databases are often used in Electronic Commerce (EC) business models such as e-brokers on the Web. To flexibly model such applications, we need a modeling language for EC business processes. To this end, we have adopted a query language approach and have designed a query language, called XBML, for decentralized XML databases used in EC businesses. In this paper, we explain and validate the functionality of XBML by specifying e-broker business models and describe the implementation of the XBML server, focusing on the distributed query processing.

It is necessary condition for digital watermarking method for embedding memos or index data into digital photograph and so on that anyone can extract embedded data without specific keys or secret information. In this paper, we propose a data hiding technique for embedding index data into color images using wavelet transform. The proposed method keeps image quality and robustness against JPEG compression and general image processing using quantitative relation of wavelet coefficients.

Near-optimality of subcodes of the cyclic Hamming codes is demonstrated on the binary additive channel whose noise process is the two-state homogeneous Markov chain, which is a model of bursty communication channels.

The heterogeneous autonomous decentralized system technology offers a way to integrate different types of context-related autonomous decentralized (sub) systems into a coherent system. The aim of this research is to model and evaluate the communication capacity among the subsystems connected by communication gateways of a heterogeneous autonomous decentralized system. Failures of subsystems and communication gateways in the system are taken into account. We use graphs to represent the topologies of heterogeneous autonomous decentralized systems and use the residual connectedness reliability (RCR) to characterize the communication capacity among its subsystems connected by its gateways. This model enables us to share research results obtained in residual connectedness reliability study in graph theory. Not to our surprise, we learnt soon that computing RCR of general graphs is NP-hard. But to our surprise, there exist no efficient approximation algorithms that can give a good estimation of RCR for an arbitrary graph when both vertices and edges may fail. We proposed in this paper a simulation scheme that gave us good results for small to large graphs but failed for very large graphs. Then we applied a theoretical bounding approach. We obtained expressions for upper and lower bounds of RCR for arbitrary graphs. Both upper and lower bound expressions can be computed in polynomial time. We applied these expressions to several typical graphs and showed that the differences between the upper and lower bounds tend to zero as the sizes of graphs tend to infinite. The contributions of this research are twofold, we find an efficient way to model and evaluate the communication capacity of heterogeneous autonomous decentralized systems; we contribute an efficient algorithm to estimate RCR in general graph theory.

We describe a new system for high-speed wireless access systems between base stations and mobile terminals. In the proposed system, the base station has an array antenna and tracks mobile terminals by using a new tracking algorithm. A radio-on-fiber technique is used to simplify and miniaturize the components of the base station. Estimating the direction-of-arrival of the signals from a mobile terminal is important in implementing the proposed system. We propose a new tracking algorithm that uses directions-of-arrival, angular velocities of mobile terminals, and scatter modeling in multipath communications channels to improve the tracking performance. We also developed experimental equipment to demonstrate the feasibility of the proposed millimeter-wave broadband wireless access system and the efficiency of the tracking algorithm using an array antenna system. In this paper, we describe our system and present a new approach for tracking mobile terminals, which is the key feature of the system. We also discuss our simulation and experimental results.

This study investigates the problem of unfairness when QoS routing does not consider the mix of traffic classes. Unfairness is mainly caused by routing different traffic flows of the same class through paths with extremely different traffic mixtures, involving various service classes. Next, a new routing scheme--Service-sensitive Routing (SSR), which takes the state of traffic mixture of the various service classes into account, is proposed. To determine the QoS route for a flow request, SSR not only considers the available bandwidth and delay of the candidate paths, but also considers the mix of traffic classes on the paths. Additionally, the hybrid granularity routing decision in SSR scheme is scalable and suitable for the Differentiated Services and MPLS networks. Extensive simulations show that SSR can effectively reduce the variance of the average of queuing delays, for example by approximately 20% to 35% for a moderate offered load, compared to the shortest path routing. Furthermore, this routing scheme reduces the fractional reward loss and bandwidth blocking probability.

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

This paper presents a formalism for the analysis of e-commerce protocols. The approach integrates logics and process calculi, providing an expressive message passing semantics and sophisticated constructs for modeling principals. A common set of inference rules for communication, reduction and information analysis supports proofs about message passing, the knowledge and behavior of principals, and protocol properties. The power of the formalism is illustrated with an analysis of the NetBill Protocol.

We present a 5.8 GHz VCO for the 5 GHz HIPERLAN/2 and U-NII band. The VCO uses a center-tapped inductor and a substrate shield to improve phase noise. Sensitivity to supply voltage and temperature is reduced by an amplitude control block. The design is based on a distributed inductor model which allows optimization without antecedent inductor measurements. The circuit is fabricated in a 0.8 µ m 45 GHz fT low-cost SiGe-HBT technology and operates with a supply voltage of -2.0 V to -3.3 V .

This paper proposes a vector quantization scheme which makes it possible to consider the dynamics of input vectors. In the proposed scheme, a linear transformation is applied to the consecutive input vectors and the resulting vector is quantized with a distortion measure defined by the statistics. At the decoder side, the output vector sequence is determined using the statistics associated with the transmitted indices in such a way that a likelihood is maximized. To solve the maximization problem, a computationally efficient algorithm is derived. The performance of the proposed method is evaluated in LSP parameter quantization. It is found that the LSP trajectories and the corresponding spectra change quite smoothly in the proposed method. It is also shown that the use of the proposed method results in a significant improvement of subjective quality.

In this paper we summarize the actual status of the GaN/AlGaN HFET power technology at DaimlerChrysler using high quality structures grown by MOCVD on sapphire or semi-insulating SiC supplied by Epitronics. High mobilites and record extrinsic transconductance and current values were achieved on devices with sapphire and SiC substrate. Small area devices with 0.3 µm gate length yield fT=43 GHz and fmax=78 GHz (s.i. SiC substrate). Load-pull characterisation have been performed on multifinger HFETs up to 20 GHz with e.g. output power levels above 3 Watt cw at 15 GHz for a single 1.6 mm device. Though the achieved results are very promising, the performance of these devices is still hampered by transient effects on different time scales. We will show in this paper that passivation of the devices by SiN could considerably improve the RF power performance as well as reduce long time constant effects present before passivation.

Before we gave a fast generalized minimum distance (GMD) decoding algorithm for one-point algebraic-geometry (AG) codes. In this paper, we propose another fast GMD decoding algorithm for these codes, where the present method includes an erasure deletion procedure while the past one uses an erasure addition procedure. Both methods find a minimal polynomial set of a given syndrome array, which is a candidate for an erasure-and-error locator polynomial set constrained with an erasure locator set of each size. Although both erasure addition and deletion GMD decoding algorithms have been established for one-dimensional algebraic codes such as RS codes, nothing but the erasure addition GMD decoding algorithm for multidimensional algebraic codes such as one-point AG codes have been given. The present erasure deletion GMD decoding algorithm is based on the Berlekamp-Massey-Sakata (BMS) algorithm from the standpoint of constrained multidimensional shift register synthesis. It is expected that both our past and present methods play a joint role in decoding for one-point AG codes up to the error correction bound.

We report here on the electrical and structural characteristics of InGaP/GaInAsN DHBTs with up to a 50 mV reduction in turn-on voltage relative to standard InGaP/GaAs HBTs. High p-type doping levels ( 3 1019 cm-3) and dc current gain (βmax up to 100) are achieved in GaInAsN base layer structures ranging in base sheet resistance between 250 and 750 Ω/. The separate effects of a base-emitter conduction band spike and base layer energy-gap on turn-on voltage are ascertained by comparing the collector current characteristics of several different GaAs-based bipolar transistors. Photoluminescence measurements are made on the InGaP/GaInAsN DHBTs to confirm the base layer energy gap, and double crystal x-ray diffraction spectrums are used to assess strain levels in the GaInAsN base layer.

Autonomous Information Service System is a proposition made to cope with the continuously changing conditions of service provision and utilization in current information systems. The faded information field (FIF), sustained by push/pull mobile agent technology, is such a distributed architecture that brings high-assurance of the system through a balanced selective replication of the information. When the demand changes, the information environment is restructured so that the same response time to services for all unspecified users can be achieved whatever the demand volume. However, once the structure is fixed, dispatching the randomly incoming requests on the FIF is still required to guarantee the same quality of service. Our goal is to warrant the autonomous dispatching of the pull mobile agents to adjust the continuously evolving arrival distribution of the demand to the current information environment. In this paper, we explain the concepts and realization of autonomous navigation under the goal of an autonomous load balancing of the pull mobile agent volume in the FIF structure. The appropriateness of this method for FIF environments has been shown by simulation.

There is an ever-increasing demand for better performance and scalability in workflow systems. We describe how mobile agents can be used to satisfy such a requirement. For the purpose two important design issues are pointed out in workflow execution and architecture levels. Agent delegation models and a 3-layer architecture are suggested in mobile agent based workflow systems as a solution for each consideration. Workload is statically distributed over task performers based on the proposed method. As a result the performance and the scalability are improved. The effectiveness is shown through stochastic Petri-nets simulation through comparison with client-server based- and another mobile agent-based workflow systems.

This paper introduces current-mode biquad using multiple current output operational transconductance amplifiers (OTAs) and grounded capacitors. The circuit configuration is obtained from a second-order integrator loop structure with loss-less and lossy integrators. The proposed circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions by suitably choosing the input and output terminals. And the circuit characteristics can be electronically tuned through adjusting the transconductance gains of OTAs. It is also made clear that the proposed circuit has very low sensitivities with respect to the circuit active and passive elements. An example is given together with simulated results by PSpice.

The IETF Differentiated Services (DiffServ) framework achieves scalability by (1) aggregating traffic flows with coarse grain QoS on the data plane, and (2) allocating network resources with a bandwidth broker (BB) on the control plane. However, there are many issues that need to be addressed under such framework. First, it has been shown that the concatenation of strict priority (SP) scheduler of class-based queues (CBQ) can cause delay jitter unbounded under certain utilization, which is not acceptable to support the premium service (PS). Furthermore, it is not clear how such a DiffServ network can support traffic flows requiring the guaranteed service (GS), which is a desirable feature of the future Internet. This paper presents architecture and mechanisms to support multiple QoS under the DiffServ paradigm. On the data plane, we present a node architecture based on the virtual time reference system (VTRS). The key building block of our node architecture is the core-stateless virtual clock (CSVC) scheduling algorithm, which, in terms of providing delay guarantee, has the same expressive power as a stateful weighted fair queueing (WFQ) scheduler. With the CSVC scheduler as our building block, we design a node architecture that is capable of supporting integrated transport of the GS, the PS, the assured service (AS), and the traditional best effort (BE) service. On the control plane, we present a BB architecture to provide flexible resource allocation and QoS provisioning. Simulation results demonstrate that our architecture and mechanisms can provide scalable and flexible transport of integrated traffic of the GS, the PS, the AS, and the BE services.

The imprecise computation is one of the promising schemes in the real time systems to adapt quality of computations to change of load with keeping the deadlines of tasks in the systems. When overload occurs in the systems, the minimum requirements on the deadline are assured by decreasing quality of the computation. This paper describes how to apply the concept of the imprecise computation to automobile control in the expressway assuming the intelligent transportation system (shortly, ITS). The deadline violation of tasks for automobile control in the expressway induces collision of automobiles. Regardless of whether the expressway is congested or not, collision of automobiles must be avoided. To satisfy such requirement, the concept of the imprecise computation is effective. This paper proposes an adaptive scheduling using the imprecise computation to avoid collision of automobiles and increase throughput, and shows results of simulation experiments about an adaptive scheduling for automobiles control.