A per-connection end-to-end call admission control (CAC) problem is solved in this paper to allocate network resources to an input session to guarantee its quality of service (Qos) requirements. In conjunction with the solution of the CAC problem, a traffic descriptor is proposed to describe the loss rate and the delay bound Qos requirements of the connection to be set up as well as the statistical characteristics of the associated input traffic which is modeled as a linear mean function plus a (zero-mean) fractional Brownian motion. The information in the traffic descriptor is sufficient to determine the allocation of channel bandwidth and buffer space to the input traffic in a network which employs leaky bucket shapers and scheduling algorithms to guarantee the Qos requirements. The CAC problem is solved by an iterative algorithm of which there are two stages in each iteration: one is responsible for the search of a candidate end-to-end routing path and the other for the verification of the legitimacy of this candidate path to meet the Qos requirements and for the allocation of resources in such a legitimate path.

This work presents a scalable and high performance prediction protocol for optical networks. In the proposed protocol, we develop a mathematical model to maintain the stability of a network system by prediction based on the traffic temporal locality property. All the critical factors, including transceiver tuning time, propagation delay, and processing time for dealing with control packets, are considered in the proposed prediction protocol. Furthermore, our protocol can resolve the bottlenecks attributed to control signaling and electronics processing. The performance evaluation reveals that the proposed scheme can yield the higher bandwidth efficiency and incur a lower packet delay than those of the TDM and conventional reservation schemes. Also, the proposed protocol can flexibly support any scaled network system such as MANs or LANs.

We present an architecture of a VOD system employing proxy servers. The proposed VOD system provides efficient and reliable VOD services and solves the problems caused by traditional VOD systems of centralized, hierarchical or distributed architecture. The proxy servers are placed between video servers and user systems. The proxy server is a small size video server that has not only caching function but also intelligence such as VCR-like video stream control or navigation of other proxy/video servers to search for a selected video program. Using a VOD system of the proposed architecture, the VOD services can be provided to more users because it reduces the workload of video servers and network traffic. We provide the performance model of the system. Service availability is also analyzed. The proposed architecture shows better performance and availability than the traditional VOD architectures.

A software requirements specification (SRS) is a document at the first phase of software development. Since it is difficult to make an accurate SRS at the beginning of software development, we propose a supporting method to detect and interpret the inconsistency of SRS. First, we classify and define the inconsistency of SRS. Next, we describe how to detect and interpret the inconsistency of SRS. We use the Requirements Frame Model to detect the inconsistency of SRS. We apply the Dempster and Shafer's theory to interpret the inconsistency of SRS. We illustrate our method with an example.

In order to maintain the communications quality at a target level, signal-to-interference ratio (SIR)-based transmission power control methods have been developed in CDMA cellular systems. These power control methods, however, do not necessarily improve system efficiency when there is a large geographic deviation in traffic because they only control power levels. A shift in the cell boundary can control traffic balance between cells. In this paper, we evaluate the optimum location of the cell boundary and the power levels when a mobile station adaptively selects a base station (BS) for each of uplink and downlink under non-uniform traffic. Because of the asymmetry in system structure between uplink and downlink, the optimum cell boundaries are not always coincident for both the two links; the location of the cell boundary is found to migrate according to the loss in orthogonality in the downlink.

Coding scheme for a noisy multiple-access adder channel is proposed. When a T-user δ-decodable affine code C is given a priori, a qT-user λ δ-decodable affine code C* is produced by using a q q matrix B satisfying BA=λ Iq q, e. g. , a Hadamard matrix or a conference matrix. In particular, the case of δ=1 is considered for the practical purposes. A (2n-1)-user uniquely decodable (δ=1) affine code Cn with arbitrary code length n is recursively constructed. When Cn plays a role of C, a q(2n-1)-user λ-decodable affine code C* is obtained. The code length and the number of users of C* are more flexible than those of the Wilson's code. The total rate of the λ-decodable code in this paper tends to be higher than that of the λ-decodable code by Wilson as the number of users increases.

This paper reviews the present EMC technology level, introduces the problems to be investigated in the near future from the viewpoint of design technology, test and measurement and systems safety, and proposes what is a goal of technology level of EMC to be established for circuits, equipments and systems.

In this paper, a method for finding the direction of arrival (DOA) of a single short pulse is proposed. The method is based on a waveform reconstruction technique using complex antenna factors (CAF). Since the frequency characteristics of CAF has angle dependency, the DOA of an electromagnetic pulse can be determined by the waveforms reconstructed with CAF. The results of a simulation and an experiment show the possibility to apply the two-dimensional DOA finding.

Increasing traffic on the Internet and intranets has raised demands for high-speed, large-scale and cost-effective computer networking techniques. ATM connectionless service provides high-speed, highly scalable, and flexible services because connectionless networks are constructed logically over high-speed ATM networks. This paper described the self-sizing operation for high-speed, large-scale connectionless service over an ATM network. Self-sizing is an autonomous adjustment mechanism for virtual path (VP) bandwidths based on traffic conditions observed in real time. We confirmed its feasibility on a test-bed network. The self-sizing operation caused the VP bandwidth to approach the necessary value while satisfying the target cell loss ratio (CLR). We developed an operations system (OpS) that achieves self-sizing in an ATM connectionless network. The OpS suggests necessary bandwidth for VP that may exceed the target CLR. The algorithm utilized in the OpS does not require observation or logical processes, which would be a heavy load on each node. Self-sizing operation will provide easy and cost-effective management because it adjusts VP bandwidth flexibly depending on the current traffic demand.

The design of effective traffic and resource management policies is a key issue in the deployment of ATM-satellite systems. This paper proposes a technique of call admission control and dynamic resource management to support ATM traffic classes in satellite environments. The effectiveness of the strategy is assessed by referring to the EuroSkyWay multimedia satellite platform, based on Ka-band payload and on-board processing. The main advantage is the effective exploitation of the satellite bandwidth by means of the statistical multiplexing of traffic sources and the guarantee of QoS provisioning to both real-time and non real-time, constant and variable bit rate sources.

ABR service is currently standardized to handle applications of data traffic in ATM network. As a flow control method, the rate-based flow control has been adopted and applied to manage the ABR service. Several control methods have been proposed, and the EPRCA is selected as one of the control methods by the ATM Forum. EPRCA is an excellent algorithm, but when the EPRCA is applied to the ATM network, several problems occur. One of the problems is the beat-down problem, which gives unfair allocation of transmission rate to connections. We propose a new control method which solves the beat-down problem. We will show that, by our proposed method, (i) the ACR is given fairly to every connection compared to the conventional method, and also (ii) the throughput is fair for both long-hop and short-hop connections, (iii) the ACR is proportional to the throughput, and finally (iv) the total throughput is larger than that of the conventional method. The fairness of the throughput in (ii) is measured by the fairness index. In (iii), being proportional means that the allocated ACR is close to the throughput and it is measured by the proportion index. The performance is evaluated by computer simulation.

In this paper, we propose an analytic method for dimensioning traffic descriptors at the leaky bucket-based UPC for VBR MPEG video traffic on ATM networks. We analytically derived cell violation probabilities at the UPC by using a proposed scene-based video traffic model, and then we showed that it was possible to select sets of traffic descriptors that produce the required violation probability. In two example video traces, the numerical results showed that our proposed traffic descriptor dimensioning method well approximated the simulation-based traffic control results of the real video traces. In cases where an effective bandwidth allocation method based on the ON/OFF model was used for the call admission control in the networks, we compared the allocated effective bandwidth to each set of traffic descriptors that produced zero UPC losses.

A novel electrical gating circuit is proposed for ultrafast applications in electronics. The circuit employs a two-conductor coupled line, and does not have any active devices such as transistors or diodes. Hence, the ultimate speed of the circuit is limited only by the cutoff frequency of the lines employed. The authors describe the circuit theory and discuss the results of experiments that involved ultrafast measurement using electro-optic sampling techniques. The latter suggests the potential of the circuit to achieve the gatings of at least 80-Gbit/s.

In Asynchronous Transfer Mode (ATM) networks, congestion can be caused by unpredictable statistical fluctuations of traffic flows and fault conditions within the network. If congestion happens, then the network performance for the already established connection will decrease. ATM networks use the preventive congestion control mechanisms such as Usage Parameter Control (UPC) and Connection Admission Control (CAC) to avoid congested conditions. Knowing that many sources in ATM networks have variable traffic stream with different QoS characteristics, traffic management functions become necessary to control the traffic flows within the network. By using the signaling procedures at the call setup phase, the network and source reach an agreement for some traffic characteristic parameters. If the source violates the traffic parameters, then the probability of congestion increases. So the network must control the source traffic streams and detect well the violating cells. Therefore, fast detection of any violating source is one of the most important characteristics of a good traffic policer. In this paper we propose a fuzzy traffic policer with high ability in detection of violating sources. Our proposed fuzzy controller has two inputs, estimated passed mean cell rate and the current state of the counter. If the output of fuzzy controller is 1, then the input cell is detected as violating cell, otherwise it is a non-violating cell. Simulation results obtained from two traffic sources, show that the proposed traffic policer has better selectivity than the conventional leaky bucket. It is observed that our proposed traffic policer has better ability for mean cell rate control, peak cell rate control and burst duration control. Furthermore, it is observed that the proposed traffic policer outperforms the conventional leaky bucket specially when the dynamic behavior is considered.

Future cellular communication systems will be called upon to provide multimedia services (voice, data, and video) for various user platforms (pedestrians, cars, and trains) that have a variety of mobility characteristics. Knowledge of mobility characteristics is essential for planning, designing and operating communication networks. The position data of selected vehicles (taxis) have been measured by using the Global Positioning System at 1-s intervals. Those data are used for evaluating mobility characteristics, such as probabilistic distributions of speed, cell dwell time, and cell crossover rate of vehicles, assuming that cells are hypothetically laid over the loci of the vehicles. The cell dwell time of vehicles is found to follow a lognormal distribution, rather than a conventionally-presumed negative exponential distribution. When the holding time distribution and random origination of calls along the loci are assumed, the properties of the cell dwell time and the handoff rate of terminals communicating in the hypothetical cellular systems are also estimated from the measured data.

As VLSI technology has developed, the interest in implementing an entire or significant part of a parallel computer system using wafer scale integration is growing. The major problem for the case is the possibility of drastically low yield and/or reliability of the system if there is no strategy for coping with such situations. Various strategies to restructure the faulty physical system into the fault-free target logical system are described in the literature [1]-[5]. In this paper, we propose an efficient approximate method which can reconstruct the 1 1/2 track-switch mesh arrays with faulty PEs using hardware as well as software. A logical circuit added to each PE and a network connecting the circuits are used to decide spare PEs which compensate for faulty PEs. The hardware compexity of each circuit is much less than that of a PE where the size of each additional circuit is independent of array sizes and constant. By using the exclusive hardware scheme, a built-in self-reconfigurable system without using a host computer is realizable and the time for reconfiguring arrays becomes very short. The simulation result of the performance of the method shows that the reconstructing efficiency of our algorithm is a little less than those of the exaustive and Shigei's ones [6] and [7], but much better than that of the neural one [3]. We also compare the time complexities of reconstructions by hardware as well as software, and the hardware complexity in terms of the number of gates in the logical circuit added to each PE among the other methods.

This paper describes the effects of traffic distributions on uplink and downlink communications qualities in CDMA cellular systems. Many researches have been done from the viewpoint of the system capacity under ideal conditions in both uplink and downlink. However, there are few studies regarding traffic distributions that concurrently affect the uplink and downlink quality. The characteristics in both links are different even in a spatially uniform traffic distribution because the system structures are not symmetric between both links. When non-uniform radio environments are assumed, both link qualities become very different from each other. It is therefore important to design systems in consideration of link-specific characteristics in whole service area. This paper clarifies the difference in both link characteristics in CDMA systems regarding traffic distributions.

A method to recognize planar objects undergoing affine transformation is proposed in this paper. The method is based upon wavelet multiscale features and Hopfield neural networks. The feature vector consists of the multiscale wavelet transformed extremal evolution. The evolution contains the information of the contour primitives in a multiscale manner, which can be used to discriminate dominant points, hence a good initial state of the Hopfield network can be obtained. Such good initiation enables the network to converge more efficiently. A wavelet normalization scheme was applied to make our method scale invariant and to reduce the distortion resulting from normalizing the object contours. The Hopfield neural network was employed as a global processing mechanism for feature matching and made our method suitable to recognize planar objects whose shape distortion arising from an affine transformation. The Hopfield network was improved to guarantee unique and more stable matching results. A new matching evaluation scheme, which is computationally efficient, was proposed to evaluate the goodness of matching. Two sets of images, noiseless and noisy industrial tools, undergoing affine transformation were used to test the performance of the proposed method. Experimental results showed that our method is not only effective and robust under affine transformation but also can limit the effect of noises.

Internet communication is increasingly becoming an important element in daily life. Keeping this network safe from malicious elements is an urgent task for network management. To maintain the security level networks are generally, monitored for indications of usage with ill-intentions. Such indications are events which need to be collated, correlated and analyzed in real-time to be effective. However, on an average medium to large size network the number of such events are very large. This makes it practically impossible to analyze the information in real-time and provide the necessary security measures. In this paper, we propose a mechanism that keeps the number of events, to be analyzed, low thereby making it possible to provide ample security measures. We discuss a real-time Intrusion Detection System (IDS) for detecting network attacks. The system looks out for TCP ACK/RST packets, which are generally caused by network scans. The system can extract the tendency of network flows in real-time, based on the newly developed time-based clustering and Dynamic Access Tree creation techniques. The algorithm, implemented and deployed on a medium size backbone network using RMON (Remote MONitoring) technology, successfully detected 195 intrusion attempts during a one month period. The results of the pilot deployment are discussed. In this paper, the proposal, implementation and evaluation will be described.

With the knowledge of the syndromes Sa,b, 0a,b q-2, the exact error values cannot be determined by using the conventional (q-1)2-point discrete Fourier transform in the decoding of a plane algebraic-geometric code over GF(q). In this letter, the inverse q-point 1-dimensional and q2-point 2-dimensional affine Fourier transform over GF(q) are presented to be used to retrieve the actual error values, but it requires much computation efforts. For saving computation complexity, a modification of the affine Fourier transform is derived by using the property of the rational points of the plane Hermitian curve. The modified transform, which has almost the same computation complexity of the conventional discrete Fourier transform, requires the knowledge of syndromes Sa,b, 0 a,b q-2, and three more extended syndromes Sq-1,q-1, S0,q-1, Sq-1,0.