In this paper, we consider the problem of multicast routing and wavelength assignment (MC-RWA) in multi-fiber all-optical WDM networks. Two main network design system comprehensively investigated here are mesh and multi-ring designs. Given the multicast traffic demands, we present new ILP formulations to solve the MC-RWA problem with an objective to determine the minimal number of fibers needed to support the multicast requests. Unlike previous studies, our ILP formulations are not only capable of finding the optimal multicast routing and wavelength assignment pattern to the light-trees, but also finding the optimal light-tree structures simultaneously. Since broadcast and unicast communications are special cases of multicast communications, our ILP models are actually the generalized RWA mathematical models of optical WDM networks. In addition to proposing the ILP models, this paper takes two main issues affecting the network capacity requirement into account, that is, the splitting degree level of optical splitters and techniques of wavelength assignment to the light-trees. Three multicast wavelength assignment techniques studied in this paper are Light-Tree (LT), Virtual Light-Tree (VLT) and Partial Virtual Light-Tree (PVLT) techniques. Due to the NP-completeness of the MC-RWA problem, the ILP formulations can reasonably cope with small and moderate networks. To work with large networks, this paper presents alternative MC-RWA ILP-based heuristic algorithms for the PVLT and LT networks and develops lower bound techniques to characterize the performance of our algorithms. Using existing large backbone networks, numerical results are reported to analyze such aspects as multiple fiber systems, the benefits of using optical splitters and wavelength converters, and the capacity difference between the mesh and multi-ring designs. Finally, this paper provides an analysis of the influence of network connectivity on the network implementation under the constraints of mesh and multi-ring design schemes.

An efficient data transmission interface for VLSI systems, Multi-Bit Parallel Code Division Multiple Access (MB/P-CDMA) interface, has been designed with 0.35 µm CMOS technology. The proposed interface achieves 1.12 Gb/s data rate (80 MHz, 8 bit bus) using multi-bit transmission at each clock per transmitter. The proposed CDMA interface ensures higher speed operation than conventional interface even in noisy environments. Each of the transmitters and receivers occupies the die area of 290 360 µm2 and 240 280 µm2, respectively.

Spectral-amplitude coding (SAC) techniques in fiber-Bragg-grating (FBG)-based optical code-division multiple-access (OCDMA) systems were investigated in our previous work. This paper adopts the same network architecture to investigate the simultaneous reductions of multiple-access interference (MAI) and optical beat interference (OBI). The MAI is caused by overlapping wavelengths from undesired network coder/decoders (codecs) while the OBI is induced by interaction of simultaneous chips at adjacent gratings. It is proposed that MAI and OBI reductions may be obtained by use of: 1) a source spectrum that is divided into equal chip spacing; 2) coded FBGs characterized by approximately the same number of "0" and "1" code elements; and 3) spectrally balanced photo-detectors. With quasi-orthogonal Walsh-Hadamard coded FBGs, complementary spectral chips is employed as signal pairs to be recombined and detected in balanced photo-detectors, thus achieving simultaneous suppression of both MAIs and OBIs. Simulation results showed that the proposed OCDMA spectral-amplitude coding scheme achieves significant MAI and OBI reductions.

A very long instruction word (VLIW) digital signal processor (DSP), called ODiN, which could execute six instructions in a single cycle simultaneously, is designed and fabricated using 0.25 µm 1-ploy 5-metal standard cell static CMOS process. The ODiN core delivers maximum 600 MIPS with 100 MHz system clock. In order to achieve high performance operation, the designed core includes compact register files, orthogonal instruction set, single cycle operations for most instructions, and parallel processing based on software scheduling. In addition, a Viterbi decoder processor and a FFT processor that are embedded make it possible to implement software defined radio (SDR) applications efficiently.

This paper presents an asynchronous data transfer scheme using 2-color 2-phase dual-rail encoding based on a differential operation and its circuit realization. The proposed encoding enables seamless asynchronous data transfer without inserting a spacer, because each logic value is represented by two kinds of codewords with dual-rail, called "color" data. Since the difference x-x between components of a codeword (x,x) becomes constant in every valid state, the data-arrival state can be detected by calculating the difference x-x. From the viewpoint of circuit implementation, during the state transition, since the dual-rail x and x are defined so as to transit differentially, the compatibility with a comparator using a differential amplifier becomes high, which results in reduction of the cycle time. It is evaluated using HSPICE simulation with a 0.18 µm CMOS technology that communication speed using the proposed dual-rail encoding becomes 1.4 times faster than that using conventional dual-rail encoding.

The optimum tier architectures for ASICs are investigated by using a methodology for predicting packing efficiency of a logic block (the ratio of total cell area to the block area including space regions between cells). In the methodology based on Rent's rule, (1) the empirical parameters required for the prediction are derived from the results of our ASIC products. (2) The concept of logic distance, which is expressed in units of the number of cells rather than the absolute net length, is introduced. (3) Not only performance constraints but also reliability constraints are incorporated. These allow us to make a quantitative comparison of the packing efficiency between various cell and tier structures. It is found that, for mega-cell blocks, all minimum-pitch layer architecture with buffer insertion is expected to give more than 20% reduction in block areas compared to the minimum-pitch + bi-pitch architecture, while satisfying the performance and reliability constraints.

This paper investigates a random-interleaver-based approach to space-time coding. The basic principle is to employ a good forward error correction (FEC) code and transmit randomly interleaved codewords over an antenna array. A low-cost estimation technique is considered. The complexity involved grows only linearly with the number of transmit antennas. Near-capacity performance can be achieved with moderate complexity.

A multifunctional Boolean logic circuit composed of single-electron transistors (SETs) was fabricated and its operation demonstrated. The functions of Boolean logic can be changed by the half-period phase shift of the Coulomb-blockade (CB) oscillation of some SETs in the circuit, and an automatic control based on a feedback process is used to attain an exact shift. The amount of charges in the memory node (MN), which is capacitively coupled to the SET, controls the phase of the CB oscillation, and the output signal of the SET controls the amount of charge in the MN during the feedback process. This feedback process automatically adjusts SET output characteristics in such a way that it is used for the multifunctional Boolean logic. We experimentally demonstrated the automatic phase control and examined the speed of the feedback process by SPICE circuit simulation combined with a compact analytical SET model. The simulation revealed that programming time could be of the order of a few ten nanoseconds, thereby promising high-speed switching of the functions of the multifunctional Boolean logic circuit.

To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

This letter proposes a hierarchical label-switched path (LSP) setup scheme, called ConSet, for multi-layer generalized multi-protocol label switching (GMPLS) networks. ConSet allows a Path message to be transmitted to the downstream neighbor node without waiting for the establishment of the higher-order LSP. Confirmation of the establishment of the higher-order LSP is performed at the ingress node of the higher-order LSP before a Resv message of the lower-order LSP is transmitted to the upstream neighbor node. ConSet is able to set up hierarchical LSPs faster than the sequential scheme.

This paper theoretically evaluates the performance of overlapping pulse-position modulation (OPPM) fiber-optic code-division multiple-access (FO-CDMA) systems in the presence of code synchronization errors. The analysis is carried out with a constraint on throughput-pulsewidth product. Discussions on effects of various system parameters, such as timing offset, index of overlap, number of users, are presented. The results show that the OPPM FO-CDMA systems with high index of overlaps have better resistance against imperfect synchronization. In fact, the acceptable performance could be maintained even with timing offsets of up to 30% of chip pulsewidth. On the other hand, strict code synchronization is necessarily required, preferably within a half code chip pulsewidth.

This paper proposes a method to detect buildings and houses whose walls are not parallel to Synthetic Aperture Radar (SAR) flight path. Experimental observations show that it is difficult to detect these targets because of small backscattering characteristics. The detection method is based on the correlation coefficient in the circular polarization basis, taking full advantage of Polarimetric SAR (POLSAR) data. Since the correlation coefficient is real-valued for natural distributed targets with reflection symmetry and for non-natural targets orthogonal to illumination direction, and it becomes a complex number for non-natural targets aligned not orthogonal to radar Line-Of-Sight (LOS), the value seems to be an effective index for detection of obliquely aligned non-natural targets. The detection results are shown using the X-band Polarimetric and Interferometric SAR (Pi-SAR) single-path data set in conjunction with other polarimetric indices.

We show that the necessary and sufficient condition for the existence of a balanced bowtie decomposition of the symmetric complete multi-digraph is n 5 and λ(n-1) 0 (mod 6). Decomposition algorithms are also given.

In this paper, a novel UWB system called pulse position controlled UWB is proposed. One of the problems in UWB systems is the restriction of data rates due to multipath. The proposed UWB system shorten the pulse interval adaptively depending on channel characteristics. It has been shown that the proposed UWB system can increase the data rate with about 30% and improve the BER at the same time.

A full-duplex radio-on-fiber (ROF) transport system based on optical single sideband (SSB) modulation, wavelength-division-multiplexing (WDM) and optical add-drop multiplexing techniques is proposed and demonstrated. A 1.5-dB RF power degradation due to the chromatic dispersion was achieved by employing optical SSB modulation scheme in the system, in which resulting in low bit error rate (BER) and third order intermodulation distortion to carrier ratio (IMD3/C) values. Such a proposed full-duplex ROF transport system is suitable for the long-haul microwave optical link.

Direct manipulation by hand is an intuitive and simple way of positioning objects in an immersive virtual environment. However, this technique is not suitable for making precise adjustments to virtual objects in an immersive environment because it is difficult to hold a hand unsupported in midair and to then release an object at a fixed point. We therefore propose an alternative technique using a virtual 3D gearbox widget that we have designed, which enables users to adjust values precisely. We tested the technique in a usability study along with the use of hand manipulation and a slider. The results showed that the gearbox was the best of the three techniques for precise adjustment of small targets, in terms of both performance data and subject preference.

In this letter, we address the problem of how to measure the link quality in terms of signal-to-interference ratio (SIR) in rapidly time varying channels which are due to fast variation of the interference or the bursty nature of the traffic. We propose a new SIR estimation approach for the TD-CDMA system, that is based on a pre-selection tentative decision device which discards and selects the estimated symbol on the basis of MAP ratio. The simulation results show that the proposed SIR estimator works and is superior to other known estimators in rapidly time varying channels.

A low-band spectrum envelope reconstruction method was tested to see if it could improve the sound quality of F0 modified speech with the PSOLA (Pitch Synchronous OverLap Add) method. In the conventional PSOLA method, the extracted spectrum envelope using a Hanning window with two-pitch-period length had no reliable information in the band of frequencies lower than the original F0. This problem causes sound degradation of the F0 modified speech when the F0 is shifted downward. In the proposed method, the low-band spectrum envelope was properly modified according to the F0 modification rate. The amplitude of the F0 harmonic components in the low-band were reproduced based on the spectral tilt of the spectrum envelope. Subjective listening tests suggest the proposed method yields improved sound quality than the conventional TD-PSOLA method when the downward modification rate exceeds 0.4 octave.

Visual defects, called mura in the field, sometimes occur during the manufacturing of the flat panel liquid crystal displays. In this paper we propose an automatic inspection method that reliably detects and quantifies TFT-LCD region-mura defects. The method consists of two phases. In the first phase we segment candidate region-muras from TFT-LCD panel images using the modified regression diagnostics and Niblack's thresholding. In the second phase, based on the human eye's sensitivity to mura, we quantify mura level for each candidate, which is used to identify real muras by grading them as pass or fail. Performance of the proposed method is evaluated on real TFT-LCD panel samples.

A bandpass filter (BPF) with shielded inverted microstrip lines (SIMSL), previously demonstrated by the author, has shown the nontrivial asymmetry of filter responses in spite of adopting a conventional filter synthesis procedure. This paper will reveal the mechanism of the asymmetry and propose prescriptions for recovering the defect, in addition to observing the wave propagation property of SIMSL. Firstly, the behavior of phase constants or effective dielectric constants for various modes propagating on single SIMSL are indicated in terms of the line configuration, and the dispersion characteristics of the quasi-TEM mode are interpreted from the point of mode coupling between the pure TEM mode and dielectric slab modes. Then it is shown that the asymmetry is dependent only on the transmission characteristics of SIMSL parallel-coupled lines involved in the filter circuits. Theoretical considerations reveal that the asymmetry is due to the fact that SIMSL has quite different phase constants for the even- and odd-mode. On the basis of these results, the optimized BPF is designed and it is experimentally demonstrated that the symmetry of its responses is notably recovered. Furthermore, this optimization is still quite efficient for achieving high attenuation properties at its harmonics.