This paper clarifies the appropriate traffic domains for combination between two database schemes (i. e. , HLR database scheme and VLR database scheme) and two call routing schemes (i. e. , Redirection Routing scheme and Look-a-head Routing scheme) in the Global Mobility Network (GLOMONET), which is able to provide global roaming service for the personal telecommunication user. The appropriate domains for combination between each scheme are shown to depend on user's mobility (i. e. the frequency of a user's access to a network where the user stays, the length of the period during which the user stays in the same network). Whether the appropriate domains for the HLR database scheme exist depends only on the frequency of the user's access to the network. When there are appropriate domains for the HLR database scheme, increasing the frequency of the user's access to the network, decreasing the length of the period the user stays in the user's home network, or increasing the length of the period the user stays in a network that isn't the user's home network widens the domains where the VLR database scheme is appropriate.

This paper proposes a new design method of nonlinear filtering and fixed-point smoothing algorithms in discrete-time stochastic systems. The observed value consists of nonlinearly modulated signal and additive white Gaussian observation noise. The filtering and fixed-point smoothing algorithms are designed based on the same idea as the extended Kalman filter derived based on the recursive least-squares Kalman filter in linear discrete-time stochastic systems. The proposed filter and fixed-point smoother necessitate the information of the autocovariance function of the signal, the variance of the observation noise, the nonlinear observation function and its differentiated one with respect to the signal. The estimation accuracy of the proposed extended filter is compared with the extended maximum a posteriori (MAP) filter theoretically. Also, the current estimators are compared in estimation accuracy with the extended MAP estimators, the extended Kalman estimators and the Kalman neuro computing method numerically.

We propose a novel planar filter design for narrow-band applications. The filter consists of half-wavelength ring resonators with open gaps. This design has three advantages over conventional planar designs: a smaller size despite narrow bandwidth, a sharper skirt response at the passband edge without notch, an excellent out-band attenuation. We demonstrated these advantages by fabricating an 8-poles filter centered at 1.95 GHz with a 5 MHz bandwidth using YBCO films on a 2 inch diameter MgO substrate.

In a personal communication system (PCS), a scheme for reforwarding call-terminating setup messages (SETUP messages) from a network or a cell station is used to guard against their loss. We have developed a method for evaluating the loss probability of a reforwarding scheme in which the network monitors the response messages from a personal station after forwarding a SETUP message to that personal station and reforwards the SETUP message only if a response message is not received. We started with a stochastic model in which messages registered in the paging-channel queue in a cell station are cyclically forwarded to the wireless area. This model corresponds to the finite-capacity M/D/1/N model with vacation time. We then added a method for calculating the "timeout" probability. Next we expanded the model into one in which the SETUP messages are reforwarded when a response message is not received by the network. This model corresponds to the M/D/1/N model with vacation time and retrials. We then added an approximate method for calculating the loss probability. Finally, using the proposed methods, we clarified the traffic characteristics of PCS call-terminating control.

A cavity-backed two-element rectangular loop slot antenna for circular polarization is presented and investigated by using the generalized network formulation based on the equivalence principle. By applying the method of moments, the magnetic current including the effect of the cavity is obtained for a thin rectangular loop slot. Two short-circuiting points are introduced on the slots to get circular polarization and symmetrical radiation pattern. The axial ratio bandwidth (3 dB) with VSWR (2) reaches 7.6%. The measured and computed results are in good agreement.

In this paper, outlines of the derivation of two recently developed finite difference beam propagation methods based on the higher-order Pad approximations are given to simulate the optical field propagation of tilted and turning waveguides. In order to investigate the accuracy and limitation for a propagation angle of these approaches, numerical results are presented for two benchmark tests. The present algorithms will offer, to our knowledge, the new beam propagation methods in optics.

Low-voltage technique for IC is getting one of the most important matters. It is quite difficult to realize a filter which can operate at 1 V or less because the base-emitter voltage of transistors can hardly be reduced. A design of a low-voltage continuous-time filter is presented in this paper. The basic building block of the filter is a pseudo-differential transconductor which has no tail current source. Therefore, the operating voltage is lower than that of an emitter-coupled pair. However, the common-mode (CM) gain of the transconductor is quite high and the CMRR is low. In order to reduce the CM gain, a CM feedback circuit is employed. The transconductance characteristic is expressed as the function of hyperbolic cosine. The designed filter is a fifth-order gyrator-C filter. The transconductor and the filter which has a fifth-order Butterworth lowpass characteristic are demonstrated by PSpice simulation. Transconductance characteristic, CMRR and stability of the transconductor are confirmed through the simulation. In the analysis of the filter, frequency response and offset voltage are examined. It is shown that the filter which has corner frequency of the order of megahertz can operate at a 1 V supply voltage.

In this paper we present a distributed routing protocol for finding two node-disjoint paths between each pair of nodes in a computer network. In the proposed protocol, each node in the network has the same procedure, which is driven by local information with respect to the network topology, such as adjacent nodes on a spanning tree in the network. Thus, the execution of the protocol can continue after changes of the network topology and load. Then, a spanning tree-based kernel construction is introduced to synchronize procedures under the distributed control of the protocol. Additionally, the routing scheme based on the protocol possesses the enhanced capabilities of alternate routes and load splitting, which cope with failures and load variations in the network. Thus, even if topology changes damage the obtained disjoint paths, the paths themselves can be updated efficiently.

The intermediate language (IL) modularizes a compiler into target processor independent and dependent parts, called the front-end and the back-end. By adding a new back-end, it is possible to port existing software from one processor to another. This paper presents a new efficient approach to achieve multiple targeting to quite different architectures using different processors as well, by translating from one IL into other existing ILs. This approach makes it possible to reuse existing back-ends. It has been successfully applied to a commercial-scale project for porting public switching system software. Since the target ILs were not predictable in advance, we provided an abstract syntax tree (AST) with attributes accessible by abstract data type (ADT) interface to convey the source language information from our front-end to back-ends. It was translated into several ILs that were developed independently. These translations made the compiler available in a very short time for different cross-target platforms and on several workstations we needed. The structure of this AST and the mapping to these ILs are presented, and retargeting cost is evaluated.

Recently, it is required to transfer continuous media over networks without QoS guarantee. In these networks, network congestion will cause transmission delay variance which degrades the quality of continuous media itself. This paper proposes a new protocol using a congestion control with two level rate control in the data transfer level and the coding level. It introduces a TCP-like congestion control mechanism to the rate control of data transfer level, which can detect the QoS change quickly, and adjust the coding rate of continuous media with time interval long enough for its quality. The performance evaluation through software simulation with multiplexing continuous media traffics and TCP traffics shows that the proposed protocol works effectively in the case of network congestion.

A distributed computing system consists of processing elements, communication links, memory units, data files, and programs. These resources are interconnected via a communication network and controlled by a distributed operating system. The distributed program reliability (DPR) in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to retrieve data files from other processing elements will be executed successfully. This reliability varies according to 1) the topology of the distributed computing system, 2) the reliability of the communication edges, 3) the data files and programs distribution among processing elements, and 4) the data files required to execute a program. In this paper, we show that computing the distributed program reliability on a star distributed computing system is #P-complete. A polynomially solvable case is developed for computing the distributed program reliability when some additional file distribution is restricted on the star topology. We also propose a polynomial time algorithm for computing the distributed program reliability with approximate solutions when the star topology has no the additional file distribution.

In a multisystem data sharing environment (MDSE), the computing nodes are locally coupled via a high-speed network and share a common database at the disk level. To reduce the amount of expensive and slow disk I/O, each node caches database pages in its main memory buffer. This paper focuses on the MDSE that uses record-level locking as a concurrency control. While the record-level locking can guarantee higher concurrency than page-level locking, it may result in heavy message traffic. In this paper, we first propose a cache coherency scheme that can reduce the message traffic in the standard locking. Then the scheme is extended to the context where lock caching and lock de-escalation are adopted. Using a distributed database simulation model, we evaluate the performance of the proposed schemes under a wide variety of database workloads.

From our previous studies, we derived the worst case cell delay within an ATM switch and thus can find the worst case end-to-end delay for a set of real-time connections. We observed that these delays are sensitive to the priority assignment of the connections. With a better priority assignment scheme within the switch, the worst case delay can be reduced and provide a better network performance. We extend our previous work on the closed form analysis to conduct more experimental study of how different priority assignments and system parameters may affect the performance. Furthermore, from our worst case delay analysis on a regulated ATM switch, network traffic can be smoothed by a leaky bucket at the output controller for each connection. With the appropriate setting on the leaky bucket parameter, the burstiness of the network traffic can be reduced without increasing the delay in the switch. Therefore, fewer buffers will be required for each active connection within the switch. In this paper, our experimental results have shown that the buffer requirement can be reduced up to 5.75% for each connection, which could be significant, when hundreds of connections are passing through the switches within a regulated ATM network.

A new type of a linear decorrelating receiver, named Pseudo-Decorrelator, for asynchronous code division multiple access systems over a Rayleigh fading multipath channel is presented in this paper. Starting with the analyis of the multiple access components of the decision statistics, the outputs of a bank of matched filters, the (K 3K) cross-correlation matrix for each bit is obtained. The non-square cross-correlation matrix is then inverted using the concept of Penrose's generalized inverse of a matrix. In this receiver, the detection process can be started before the whole sequence is received at the receiver, and computing the inverse of a (KN KN) cross-correlation matrix, generally required for linear decorrelating receivers, can be avoided because it is enough to compute only the generalized inverse of a (K 3K) cross-correlation matrix for each data bit. Here, K is the number of users and N is the length of input data sequence. Simulation results are also presented for K-user systems over a Rayleigh fading multipath channel.

For given undirected graph G[V,E] and vertices s and t, a minimal s-t separating set denoted by Ec & Vc is a minimal set of elements (edges and/or vertices) such that deletion of the elements from G breaks all the paths between s and t, where Ec and Vc are sets of edges and vertices, respectively. In this paper, we consider a problem of generating all minimal s-t separating sets, and show that the problem can be solved in O(µ(mt(n,n))) time, where m|E|, n|V|, µ is the number of minimal s-t separating sets of G, and t(p,q) is the time needed for finding q lowest common ancestors for q pairs of vertices in a rooted tree with p vertices. Since t(n,n) can be O(n), we can generate all minimal s-t separating in linear time per s-t separating set. However, the linear time algorithm for finding the lowest common ancestors is complicated, so that it is not efficient for a moderate size graph. Therefore, we use an O(nα (n))-time algorithm for finding the lowest common ancestors, and propose an algorithm to generate all minimal s-t separating sets in O(mnα(n)) time per s-t separating set, where α(n) is the pseudo-inverse of Ackermann function.

In this paper, a new multicast routing method for layered streams is proposed. This method is an extension of the weighted greedy algorithm (WGA) and uses two kinds of weight values to refine the link distance. It can cope with dynamic change in the group members without multicast tree re-construction. The method is compatible with the RSVP and can be utilized in existing shared tree type routing protocols such as CBT and PIM sparse mode. The network resources can be utilized efficiently; furthermore, the loss rate of member's requests to receive more layers can be reduced by this routing method when a sufficient number of nodes have the packet filtering function and a sufficient number of hops is permitted.

In practical logic design circuits are built by composing certain types of gates. Each gate itself is a simple circuits with one, two or three inputs and one output, which implements an elementary logic function. These functions are called the generators. For the general purpose the set of generators is considered to be functionally complete, i. e. , it is able to express any logic function under chosen rules compositions. A basis is a functionally complete set of logic functions that contains no complete proper subset. Providing compactness and expressibility of the generators the notion of a basis, however, ignores the optimality of implementations. Efficiently irreducible generating set, termed ε-basis, is an irreducible set of generators which guarantees an optimal implementation of every function, with respect to the number of literals in its formal expression. The notion of ε-basis is significant in the composition of functions, since the classical definition of basis does not consider the efficiency of implementation. In case of Boolean functions, for two-input (dyadic) generators it has been shown that an ε-basis consists of all monadic functions, constants, and only two dyadic functions from certain classes. In this paper, expanding the domain of basic operations from dyadic to triadic, we study the efficiency of sets of 3-input gates as generators. This expansion decreases the complexity of functions (hence, the complexity of functional circuits to be designed). Gaining an evident merit in the complexity, we have to pay a price by a considerable increase of the number of such generators for the multiple valued circuits. However, in the case of Boolean operations this number is still very small, and it will certainly be useful to consider this approach in the practical circuit design. This paper provides a criterion for a generating set of triadic operations of k-valued logic to be efficiently irreducible. In the case of Boolean functions it is shown that there exist exactly five types of classes of triadic operations which constitute an ε-basis. A typical example of generator set which forms a triadic ε-basis, is also shown.

This paper investigates a relationship between accepting powers of two-way deterministic one-counter automata and one-pebble off-line deterministic Turing machines operating in space between loglog n and log n, and shows that they are incomparable.

We propose two fault-tolerant broadcasting schemes in star graphs. One of the schemes can tolerate up to n2 faults of the crash type in the n-star graph. The other scheme can tolerate up to (n3d1)/2 faults of the Byzantine type in the n-star graph, where d is the smallest positive integer satisfying nd!. Each of the schemes is designed for the single-port mode, and it completes the broadcasting in O(n log n) time. These schemes are time optimal. For the former scheme we analyze the reliability in the case where faults of the crash type are randomly distributed. It can tolerate (n!)α faults randomly distributed in the n-star graph with a high probability, where α is any constant less than 1.

This paper introduces an alternating rebound Turing machine and investigates some fundamental properties of it. Let DRTM (NRTM,ARTM) denote a deterministic (nondeterministic and alternating) rebound Turing machine, and URTM denote an ARTM with only universal states. We first investigate a relationship between the accepting powers of rebound machines and ordinary machines, and show, for example, that (1) there exists a language accepted by a deterministic rebound automaton, but not accepted by any o(log n) space-bounded alternating Turing machine, (2) alternating rebound automata are equivalent to two-way alternating counter automata, and (3) deterministic rebound counter automata are more powerful than two-way deterministic counter automata. We next investigate a relationship among the accepting powers of DRTM's, NRTM's, URTM's and ARTM's, and show that there exists a language accepted by alternating rebound automata, but not accepted by any o(logn) space-bounded NRTM (URTM). Then we show that there exists an infinite space hierarchy for DRTM's (NRTM's, URTM's) with spaces below log n. Furthermore, we investigate a relationship between the strong and weak modes of space complexity, and finally show that the classes of languages accepted by o(logn) space-bounded DRTM's (NRTM's, URTM's) are not closed under concatenation and Kleene .