Wavelength division multiplexed (WDM) routed optical networks represent the direction towards future high-capacity wide-area network applications. A serious issue in WDM-routed networks, though, is light-path allocation which requires a combination of optical routing and wavelength assignment. While near-optimal-routing and wavelength-assignment algorithms aimed at minimizing network wavelength requirements have been reported, the practicability of wavelength-routed optical networks depends on the number of wavelengths required to satisfy a given traffic demand. In this paper, we proposed two symmetrical routing and wavelength-assignment methods for optical networks with a Grid or ShuffleNet physical topology. Here, we consider the case of non-adaptive wavelength routing systems, where the operations performed in nodes are independent of the network traffic load. In this case, the routing differs somewhat from that in adaptive routing networks where the routing function may produce different results at different times. The path followed by a wavelength never changes in non-adaptive wavelength-routing networks. When all N(N-1) node-pairs are to be connected, our methods lower the wavelength requirement to (or close to) its calculated minimum. Symmetry is a basic feature of both these regular topologies, but there are differences in the features within the topologies. Our goal has been to try to make use of the symmetry, and the differences in the native symmetry features, of these regular topologies to yield a lower wavelength requirement.

This paper introduces the concept of hierarchical testability of data paths for delay faults. A definition of hierarchically two-pattern testable (HTPT) data path is developed. Also, a design for testability (DFT) method is presented to augment a data path to become an HTPT one. The DFT method incorporates a graph-based analysis of an HTPT data path and makes use of some graph algorithms. The proposed method can provide similar advantages to the enhanced scan approach at a much lower hardware overhead cost.

The transfer characteristic of an integrator is affected by excess-phase shift caused by the parasitic capacitance. The phase compensation is obtained by introducing zeros to generate phase lead. This paper proposes a phase compensation technique for the differential signal input integrator. The proposed technique is employing feedforward signal current source. The fifth-order leapfrog Chebyshev low-pass filter with 0.5 dB passband ripple is designed using the integrator with the proposed phase compensation. Further, an autotuning phase compensation system using the proposed technique is realized by applying a PLL system. The effectiveness of the proposed technique is confirmed by PSPICE simulation. The simulation results of the integrator with the proposed phase compensation shows that excess-phase cancellation is obtained at various unity gain frequencies. The accurate filter characteristic of the fifth-order leapfrog filter is obtained by using the autotuning phase compensation system. The passband of the filter is improved over wide range of frequencies. The proposed technique is suitable for low voltage application.

Digitalization in electronic systems requires the electronics devices in de-coupler sets with low impedance at high frequency, and high reliability. A shield strip type line component with aluminum substrate, its surface oxidized dielectric layer and a conducting polymer electrolyte has been developed. The conducting polymers of polypyrrole and poly(3,4-ethylenedioxythiophene) have been formed by direct chemical oxidative polymerization and electrochemical polymerization on a dielectric layer. Thus, the surface of the dielectric layer is covered with conducting polymer films. The structure of the line component is strip line conformation just like a crushed coaxial cable with in-put and out-put terminals surrounded by the conducting polymer electrolyte. Two types of the components, i.e., a large surface area, 10 20 mm, and a small surface area, 4 4 mm, have been fabricated with polypyrrole and poly(3,4-ethylenedioxythiophene), respectively. The dielectric properties of these line components have been investigated with a Impedance/Gain-phase analyzer and a network analyzer. Due to the high conductivity of the polymer electrolytes, the line components demonstrate low impedance at resonance frequency. Regarding the frequency characteristics of the line components, the impedance and ESR at high frequency are lower than those of the conventional capacitors. Furthermore, the transfer coefficients, S21, are three orders lower than those of other capacitors in a wide frequency band from 10 kHz to 6 GHz. The results indicate the excellent characteristics of the line components for the power line de-coupler set at the boundary of the closed circuit unit.

The optical pulses of 50 MHz has been obtained from an organic light emitting diode (OLED) based on the Alq3 emissive layer with the active area of 0.01 mm2. We demonstrate that the OLEDs can be applied to fields of optical communication as the electro-optical conversion device for transmitting the signals of moving picture.

Organic light emitting diodes (OLEDs) containing nanostructured cathode buffer layers were fabricated, and their electrical and emitting properties were investigated. The OLEDs have an ITO anode/CuPc/TPD/Alq3/buffer layer/Al cathode structure with the buffer layers made from nanostructured alternating layers Alq3 and Al. The driving voltage and the efficiency of the devices were improved by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode.

Photoirradiation effects on the polymer light-emitting devices (PLEDs) with a semitransparent-Al cathode have been studied. A light-emitting polymers, a poly (p-phenylene vinylene) derivative MDOPPV has been used in this study. Upon photoirradiation, the emission intensity at a constant voltage was rapidly decreased. However, the quantum efficiency of electroluminescence remained constant, indicating the spatial separation between recombination zone and photooxidized defects. On the other hand, the quantum efficiency of photoluminescence rapidly dropped upon similar photoirradation. These can be understood by taking the difference in the spatial distribution and the origin of excitons between electro- and photo-luminescence processes. It was also found that the photooxidation rate of the polymer film whose thickness is ca. 100 nm does not have thickness dependence, suggesting that the photooxidation of the polymer proceeds uniformly throughout the device.

We proposed the conduction mechanism of organic light-emitting diode (OLED) using a one-dimensional discontinuous model. We assumed that each emitting molecule corresponds to a hopping site according to the actual charge transfer between adjacent molecules. Both carrier mobility of Alq3 and barrier heights for each carrier were derived from experimental data. We calculate transient behavior of carrier, field, and exciton distribution. Both carrier injections assumed the Schottky injection. In the previous results, when we assumed that calculated current density fit the experimental one in the current density field curve, calculated light-emission intensity did not fit the experimental one in the light-emission field curve. Furthermore, the slope of the calculated light emission-field curve is too small to fit the experimental one. In the previous study, hopping distance was assumed to be 1 nm. In this study, it is assumed to be 1.7 nm. We consider that field dependence of electron injection is too weak to explain only the Schottky emission. When the electron injection is assumed to be both Schottky emission and Fowler-Nordheim emission calculated light-emission field as well as the current-density field curves were fit to the curve of each experimental characteristics.

Tracking mobile users in cellular wireless networks involves two basic functions: location update and paging. Location update refers to the process of tracking the location of mobile users that are not in conversation. Three basic algorithms have been proposed in the literature, namely the distance-based, time-based, and movement-based algorithms. The problem of minimizing the location update and paging costs has been solved in the literature by considering exponentially distributed Cell Residence Times (CRT) and Inter-Call Time (ICT), which is the time interval between two consecutive phone calls. In this paper we select the movement-based scheme since it is effective and easy to implement. Applying the theory of the delayed renewal process, we find the distribution of the number of cell crossings when the ICT is a mixture of exponentially distributed random variables and the CRT comes from any distribution with Laplace transform. In particular, we consider the case in which the first CRT may have a different distribution from the remaining CRT's, which includes the case of circular cells. We aim at the total cost minimization in this case.

This letter presents a code which corrects single bit errors in any location of the word as well as l-bit burst errors occurred in an important part of the word. The proposed code is designed by product of the parity check matrix of the l-bit burst error correcting codes and the matrix which converts input unequal errors into equal errors. This letter also demonstrates the evaluation of the code, and presents the extended codes with two-level burst error correcting capabilities by interleaving.

In this paper, we propose an efficient dual-tree-based multicasting scheme with three destination-switch partition strategies on irregular switch-based networks. The dual-tree-based routing scheme supports adaptive, distributed, and deadlock-free multicast on irregular networks with double channels. We first describe a dual-tree structure constructed from the irregular networks and prove that the multicasting based on such a structure is deadlock-free. Then, an efficient multicast routing algorithm with three destination-switch partition strategies: source-switch-based partition, destination-switch-based partition, and all-switches-based partition, is proposed. Finally, we perform simulations to evaluate our proposed algorithm under various impact parameters: system size, message length, and startup time. The experimental results show that the improved tree-based multicasting scheme outperforms the usual tree-based multicasting scheme. The dual-tree-based multicasting scheme with destination-switch-based partition is shown to be the best for all situations.

In interconnection networks, deadlock recovery has been studied in routing strategy. The routing strategy for the deadlock recovery is intended to optimize the routing performance when deadlocks do not occur. On the other hand, it is important to improve the routing performance by handling deadlocks if they occur. In this paper, a routing strategy for suspensive deadlock recovery called an escape-restoration routing is proposed and its performance is evaluated. In the principle of the proposed techniques, a small amount of exclusive buffer (escape-buffer) at each router is prepared for handling one of deadlocked packets. The transmission of the packet is suspended by temporarily escaping it to the escape-buffer. After the other deadlocked packets were sent, the suspended transmission resumes by restoring the escaped packet. Evaluation results show that the proposed techniques can improve the routing performance more than that of the previous recovery-based techniques in handling deadlocks.

The circular decoding algorithm for tail-biting convolutional codes is executed using a fixed number of computations and is suitable for DSP/ASIC implementations. This letter presents the performance and complexity trade-off in the circular decoding algorithm using an analytic bound on the error probability. An incremental performance improvement is shown as the complexity increases from O(L) to O(L+10K) where L is the length of the decoding trellis and K is the constraint length. The decoding complexity required to produce the maximum-likelihood performance is presented, which is applicable to many codes of practical interest.

This paper presents the analysis of integrated voice and data cellular networks with channel borrowing. Our considered system gives higher priority to handoff calls over new calls from users' point of view and reflects each characteristics of voice and data traffic types. Data handoff calls can wait in a queue while they are in handoff areas if there are no channels available. Voice handoff calls can borrow at most l channels from data calls if there are no idle channels upon their arrivals. We mathematically model this system by applying queueing theory. Then, we analyze its performance to derive the forced termination probability of data handoff calls, the blocking probabilities of the new and handoff calls of voice and data, and the Laplace Stieltjes transform for the distribution of waiting time in a queue. In numerical results, the analytical results for the mean waiting time of data handoff calls are compared with the simulation results to validate our analytical approach. Our system is also compared with the system where channel borrowing cannot be allowed (nonborrowing system) with respect to the blocking probabilities of the new and handoff calls of voice and data, the forced termination probability of data handoff calls, the mean and the coefficient of variation of the waiting time of data handoff calls.

The advances in services using the present Internet mean that there will be increasing demand for Video on Demand (VoD) on the Internet in the near future. However, because of the best-effort characteristics of the Internet, it is important to suppress the degradation of communication quality caused by packet dropping when Internet traffic is congested. This paper focuses on MPEG transmission over the Internet, and suitable control mechanisms are established for an acceptable Quality of Service (QoS) improvement through detailed evaluation. Packets are classified using a frame-based scheme. The server applies the proposed End-to-End control scheme and shuffles the order of packets to avoid burst dropping, and may omit selected packets belonging to certain frames prior to forwarding. At the intermediate routers, transferred packets are transmitted according to Round Robin (RR) or Weighted Round Robin (WRR) scheduling, and are dropped statistically using selective Random Early Detection (RED) corresponding to frame attributes when there is congestion. We evaluate the proposed performance of transmission method using both computer simulations and empirical measurements of picture quality. The results show that when the traffic volume cannot be estimated in the intermediate routers, the combined use of RR, shuffling and conditional RED is effective, and when the traffic volume can be estimated, the combination of WRR, rate control and RED is effective.

An English auction is the most familiar type of auctions. Generally, an electronic auction has mainly two entities, the registration manager (RM) who treats the registration of bidders, and the auction manager (AM) who holds auctions. Before starting an auction, a bidder who wants to participate in English auction is registered to RM with her/his information. An electronic English auction protocol should satisfy the following nine properties, (a) Anonymity, (b) Traceability, (c) No framing, (d) Unforgeability, (e) Fairness, (f) Verifiability, (g) Unlinkability among plural auctions, (h) Linkability in an auction, and (i) Efficiency of bidding. Furthermore from the practical point of view we add two properties (j) Easy revocation and (k) One-time registration. A group signature is adapted to an English auction in order to satisfy (a), (b), and (f). However such a direct adoption suffers from the most critical drawback of efficiency in group signatures. In this paper we propose more realistic electronic English auction scheme, which satisfies all of these properties without using a group signature. Notable features of our scheme are: (1) both of bidding and verification of bids are done quite efficiently by introducing a bulletin board, (2) both properties (j) Easy revocation and (k) One-time registration are satisfied.

In this paper, a novel type of neural networks called grey neural network (GNN) is proposed and applied to improve short term load forecasting (STLF) performance. This work is motivated by the following observations: First, the forecasting performance of neural network is affected by the randomness in STLF data. That is, poor performance results from large randomness and vice versa. Second, the grey first-order accumulated generating operation (1-AGO) is reported having randomness reduction property. By the observations, the GNN is proposed and expected to have better STLF performance. The GNN consists of grey 1-AGO, the piecewise linear neural network (PLNN), and grey first-order inverse accumulated generating operation (1-IAGO). Given a set of STLF data, the data is first converted by grey 1-AGO and then is put into the PLNN to perform forecasting. Finally, the predicted load of GNN is obtained through grey 1-IAGO. For comparison, the original STLF data is also put into the PLNN itself. With identical training conditions, the simulation results indicate that with various network structures the GNN, as expected, outperforms the PLNN itself in terms of mean squared error.

We applied a Brillouin-OTDR, which is a distributed optical fiber strain sensor, to two actual concrete piles. The piles were made for use as highway foundations by on-site-pouring at construction sites and underwent load testing to ensure that their characteristics satisfied the required levels. Compressive strain caused by the load exerted on the piles was measured to an accuracy of 0.01% and a spatial resolution of 1 m. This measurement was obtained by embedding a strain-sensing optical fiber in the piles during construction. The results showed that there was good agreement between the measured strain and both the theoretical values and the values obtained with a conventional strain gauge based on electric resistance. Furthermore, the obtained strain distribution reflected the effects of friction between the pile surface and the ground. These results demonstrate the effectiveness of the Brillouin-OTDR for this kind of testing and also as a means of obtaining detailed data on the strain in concrete piles.

For the purpose of applying to 50 GHz channel spacing 10 Gb/s DWDM systems, the dispersion reduced fiber Bragg gratings (FBG) is demonstrated. This new FBG is designed by applying in optimized cosine expansion series to the refractive index profile. The 10 π-phase shifts in the refractive index profile realize both square filtering characteristics and linear phase responses resulting in reducing group delay variation in the reflective bandwidth. The FBG, fabricated according to the new design, is tested and shows more than 30 dB isolation for the adjacent channel and less than 10 psec group delay variation in the reflective bandwidth. This small dispersion leads to vast improvement of 10 Gb/s transmission performance. The power penalty of the new FBG is suppressed to 1/6 of that of conventional FBG. Furthermore, the symmetrical refractive index profile, realized by applying a cosine expansion series, shows that these optical characteristics have no dependence of the light launching direction. From these results, this new design offers an FBG suitable for the ADM used in 10 Gb/s DWDM systems.

All-optical switching operating at 1.55 µm band in fabricated GaInAsP directional couplers loaded with grating are reported experimentally. These switching operations were realized in spatially separated output ports. The devices are suitable for optical integrated circuits and would operate as all-optical routing switches in practical power level by use of optical Kerr effect and Bragg grating. Using the optical bistability in the device, latching operation for output signal can be realized in spatially separated output ports and the outputs from each port are complementary. Two all-optical gate operations, which are optical inverting operation and optically controlled switching in spatially separated output ports, are also demonstrated, where the signal and control lights have different wavelength.