The linearity of the GaAs Field Effect Transistor (FET) power amplifier is greatly influenced by the nonlinear characteristics of gate-source capacitance (Cgs) and drain-source current (Ids) for the FETs. However, previously suggested analysis methods of GaAs FET non-linearity are mainly focused on the investigations by each individual non-linear component (Cgs or Ids) without considering both non-linear effects. We analyze more accurately the non-linearity of GaAs FETs by considering non-linear effects of Cgs and Ids simultaneously. We also investigate the third-order intermodulation distortion (IMD3) of the GaAs FET in relation to source and load impedances that minimize FET non-linearities. From the simulation results by Volterra-series technique, we show that the least IMD3 is found at the minimum source resistance (RS) and maximum load resistance (RL) in the equivalent output power (Pout) contour. Simulated results are compared with the load and source pull data, with good agreement.

In this paper we study the scalability issue in the design of a centralized bandwidth broker model for dynamic control and management of QoS provisioning. We propose and develop a path-oriented, quota-based dynamic bandwidth allocation mechanism for efficient admission control operations under the centralized bandwidth broker model. We demonstrate that this dynamic bandwidth allocation mechanism can significantly reduce the overall number of QoS state accesses/updates, thereby increasing the overall call processing capability of the bandwidth broker. Based on the proposed dynamic bandwidth allocation mechanism, we also extend the centralized architecture with a single bandwidth broker to a hierarchically distributed architecture with multiple bandwidth brokers to further improve its scalability. Our study demonstrates that the bandwidth broker architecture can be designed in such a manner that it scales with the increase in the network capacity.

The capacity analysis of CDMA forward link is required to allocate high data-rate users. To solve this problem, we analyze the capacity of the CDMA forward link based on optimum power control. In a multi-cell environment, the intracell interference and intercell interference are derived. To show the capacity impact of high data-rate users, we introduce a location dependent factor, which is the ratio of intercell interference to intracell interference. Considering the location dependent factor, we propose a coordinated allocation scheme that can be used to allocate high data-rate users in sectorized cells. As a result, we show the capacity impact of high data-rate users according to location variations. The outage probability can be decreased when the coordinated allocation scheme is applied.

Currently, the most popular model in data compression theory is that of stationary ergodic sources. But there do exist sequences each of which is not emitted from any stationary ergodic source but can be compressed sufficiently by a certain algorithm. We estimate the size of the set of such sequences in terms of Hausdorff dimension.

Emerging multimedia technologies introduce the prevalent multicast transmission, and the multicast tree is determined using the time-invariant network parameters. This paper addresses the time-varying multicast tree problem and presents path selection heuristics for multicast routing to determine an alternative path for real-time applications. A network is partitioned into the optimal region, the disjoint region, and the edge cutset if a branch of the multicast tree meets the un-guaranteed QoS condition. The path selection heuristics operate during the multicast session phase to efficiently select an alternative routing path containing an edge in the edge cutset to connect the multicast tree again. The source-based heuristics PS-SPT finds the path for minimal source-to-destination delay and the sharing-based heuristics PS-DDMC for minimal total cost. These path selection heuristics can efficiently provide solutions to keep the multicast transmission reliable. Simulation results also show that the proposed heuristics can provide effective good solutions for real-time multicast transmission. PS-SPT can select a path with optimal source-to-destination delay and PS-DDMC can select a path with optimal total cost.

In future mobile communication systems, forward link may be a limiting one because emerging data services are likely to require higher data rates in the forward link than in the reverse link. In this paper, we derive joint Erlang capacity of a DS/CDMA forward link in terms of both outage probability and blocking probability for each type of traffic in a mixed traffic environment. Resource sharing algorithm and generalized Erlang model are employed to derive joint Erlang capacity of the DS/CDMA system with various types of traffics. The joint Erlang capacity reflecting both outage probability and blocking probability of each type of traffic is obtained by an approach based on virtual circuit switching perspective. We take into account effect of closed loop power control in the analysis. From numerical results, it is confirmed that blocking probability as a QoS (quality of service) parameter has a significant impact on the forward link capacity. The results of this paper can be applied to design of the DS/CDMA systems supporting wireless multimedia traffics.

This paper concerns resource planning in a VLSI assembly facility. The facility can process more than 100 sorts of WIPs (Works-In-Process) simultaneously. Specifically it performs product-mix production. An old resource estimation system, which gave a good estimation for a memory VLSI production facility, went wrong for an assembly facility. To adjust the estimation of required machinery resources of the assembly facility, a new parameter--the tuning value for the service time--is introduced. The tuning value expresses the reduction in machine utilization in the processing steps due to the product-mix. The value is empirically determined and the machinery resources can be estimated in good accuracy. Also the waiting time for processing in the incoming buffer is successfully considered in the estimation of turnaround time. However the tuning value is not enough in estimating human resources. A novel algorithm to estimate the resources for machine adjustments is proposed. The algorithm is based on a periodic assignment of multiple sorts of WIPs in a single machine, where the adjustments of machines for the product-mix are considered. The adjustments are additional operator's jobs in the product-mix. It estimates the operator request rate and machine utilization rate when multiple sorts of WIPs with different arrival rates are processed in a single machine. Finally, this resource estimation system considers the operator allocated not only to the preprocessing and postprocessing but also to the adjustments of machines for the product-mix. The estimated machinery, human resources, and turnaround time were evaluated in a real facility, and the proposed method is confirmed to be applicable in the weekly or monthly resource planning for the facility.

We propose a two-level hierarchical method for dependability evaluation of distributed systems with replicated programs and data files. Since Markov modeling is limited only to each component in this method, state explosion can be circumvented successfully. Simulation results show that the method can accomplish evaluation even for large systems for which Markov modeling is not feasible.

In order to make the ATM network fault-tolerant and the network service flexible, a method for the setting up of backup virtual paths (VP's for short) using multiagents is effective with respect to adaptability to change of network resource and user requirements, examples of which are failure of nodes and links and addition of VP's, respectively. In this method, under the assumption that candidates of backup VP's between different pairs of source and destination nodes are given, the optimum backup VP's are obtained by exchanging information among agents autonomously. First, this paper proposes measures for determining backup VP's between different pairs of source and destination nodes. Next, this paper presents simulation results to evaluate the adaptability of the method. The results show that the method efficiently obtains the optimum backup VP's even when the number of backup VP's increases and that different idle time at each destination node enables to shorten the total processing time while keeping complete detection of shared links.

This paper proposes an area/time optimizing algorithm in a high-level synthesis system for control-based hardwares. Given a call graph whose node corresponds to a control flow of an application program, the algorithm generates a set of state-transition graphs which represents the input call graph under area and timing constraint. In the algorithm, first state-transition graphs which satisfy only timing constraint are generated and second they are transformed so that they can satisfy area constraint. Since the algorithm is directly applied to control-flow graphs, it can deal with control flows such as bit-wise processes and conditional branches. Further, the algorithm synthesizes more than one hardware architecture candidates from a single call graph for an application program. Designers of an application program can select several good hardware architectures among candidates depending on multiple design criteria. Experimental results for several control-based hardwares demonstrate effectiveness and efficiency of the algorithm.

This paper proposes a new method of realizing internationlized domain names (iDN) and has been discussed at IETF (Internet Engineering Task Force). iDN allows a user to specify multi-lingual domain names, such as Japanese, Chinese, and Korean. iDN is a proper extension of the current domain name system. We have already developed an iDN implementation, named Global Domain Name System (GDNS). GDNS extends the usage of alias records, and gives reverse mapping information for multi-lingual domain names. This paper presents yet another method which introduces new Resource Record (RR) types to cover multi-lingual domain names. We have two new RR (Resource Record) types. The first new record is INAME and the other is IPTR. These two RR types can cover multi-lingual domain names. This paper also discusses the efficiency of DNS. Since DNS is a distributed database system, the performance depends on the method of retrieving data. This paper suggests a new retrieving method that can improve the performance of DNS remarkably.

We propose a new intelligent blind source separation algorithm for the mixture of sub-Gaussian and super-Gaussian sources. The algorithm consists of an update equation of the separating matrix and an adjustment equation of nonlinear functions. To verify the validity of the proposed algorithm, we compare the proposed algorithm with extant methods.

In this manuscript, two key agreement protocols which are resistant to a denial-of-service attack are constructed from a key agreement protocol in [9] provably secure against passive and active attacks. The denial-of-service attack considered is the resource-exhaustion attack on a responder. By the resource-exhaustion attack, a malicious initiator executes a key agreement protocol simultaneously as many times as possible to exhaust the responder's resources and to disturb executions of it between honest initiators and the responder. The resources are the storage and the CPU. The proposed protocols are the first protocols resistant to both the storage-exhaustion attack and the CPU-exhaustion attack. The techniques used in the construction are stateless connection, weak key confirmation, and enforcement of heavy computation. The stateless connection is effective to enhancing the resistance to the storage-exhaustion attack. The weak key confirmation and the enforcement of heavy computation are effective to enhancing the resistance to the CPU-exhaustion attack.

The Direct-Sequence Code Division Multiple Access (DS-CDMA) is one of the most likely candidates for the 3rd generation mobile communication systems. On the other hand, a network supporting integrated data transfer and providing predictable qualities of service (QoS) to such application is an attractive issue. This paper proposes several schemes based on the majority rule concerned with resource reservation to investigate the performance of a CDMA cellular system. The admission control is based on the residue capacity and required signal-to-noise ratio (SNR) for multimedia traffic including voice, data and video. The system performance is explored with variable spreading gain and multi-code CDMA systems under the proposed schemes. Moreover, several system parameters including the handoff probability (lifetime in a cell) and the traffic load are investigated to study the impact to system performance. The results show the trade-off between the blocking probability of new calls and dropping probability of handoff calls under diversified situations. However, it is inefficient under resource reservation due to unused capacity. In this paper, we also propose a resource-borrowing scheme to improve system performance. Simulation results show that our proposed algorithm really improves the system performance in a multimedia CDMA cellular system with resource reservation.

FDMA/TDMA non-geostationary earth orbit satellite systems (Non-GEOS) generally require a pre-planned pool of radio resource, i.e., frequency and time slot plan (FTSP), for each gateway earth station (GES) prior to the real-time channel assignment by the multiple GES's sharing the resources harmoniously. The time-variant nature of those systems implies that a dynamic FTSP planning method is crucial to the operation to cope with the time-variant traffic demand and the inter-beam interference condition. This paper proposes and compares three algorithms (Serial-numbering, DP-based, and Greedy algorithms) mixed with two strategies (concentrated- and spread-types) for the resource allocation. The numerical evaluation demonstrates that Greedy algorithm with the spread-type strategy is very effective and promising with feasible calculation time for the FTSP generation.

In this paper, CAC (Call Admission Control) algorithms where decisions are based on total received power for the reverse link in CDMA systems with multiple types of services are proposed. The proposed CAC schemes have advantages in that they have control over the cell load dynamically and guarantee the required SIR, that is, QoS (quality of service). The optimal ratio of required transmission power that achieves the maximum capacity is derived for evaluating the cell load and SIR (signal to interference ratio) reflected in total received power at base stations. Allocation of different thresholds can be made for different services which can be regarded as priority based schemes. Two types of services, voice and data, are considered and the maximum throughput is obtained when threshold values are the same. In addition, the transmitter removal scheme is adopted that eliminates calls when the system does not meet the required SIR. Simulation results are provided to evaluate the performance.

We propose a blind source separation algorithm for the mixture of finite alphabet sources where sensors are less than sources. The algorithm consists of an update equation of an estimated mixing matrix and enumeration of the inferred sources. We present the bound of a step size for the stability of the algorithm and two methods of assignment of the initial point of the estimated mixing matrix. Simulation results verify the proposed algorithm.

To provide cellular data services with differentiated QoS, a shared resource scheme, based on the optimization theory and LaGrange λ-calculus was developed. This scheme can generate a fair schedule for a diverse mix of traffic with diverse QoS requirements in a limited radio spectrum. We define the acceptance indication, AI, as the QoS measurement for the shared resource scheme. The experimental results show that this approach outperforms other existing schemes.

Recently we have studied the performance of the VS/VD behavior for two binary feedback congestion control schemes, FECN and BECN, when they are applied to multicast ABR services. It is shown that the VS/VD schemes alleviate the problems of consolidation noise and consolidation delay, which are two major design issues in multicast congestion control. To complement, we further explore the VS/VD behavior for the explicit rate feedback control scheme in this letter. Through an efficient rate estimation method, it is again observed that VS/VD behavior performs better than the traditional end-to-end schemes.

If the direction of arrival (DOA) of a source is perturbed due to some reasons in a statistical way as in the environment of wireless mobile communications, a new model appropriate for such environment should be used instead of the point source model. In this paper, an angle-perturbed source model is proposed and an estimation method based on the eigen-decomposition technique is investigated under the model. The asymptotic distribution of the estimation errors is obtained to see the statistical properties.