This paper presents a cell search scheme embedded with carrier frequency synchronization for inter-cell asynchronous orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) systems. Several subcarriers are dedicated to a differentially encoded synchronization channel (SCH). In the other subcarriers, data symbols and pilot symbols are two-dimensionally spread in the time-frequency domain. The cell search scheme consists of a three-stage cell search and a two-stage carrier-frequency synchronization, that is, coarse carrier-frequency acquisition, fast Fourier transform window-timing detection, SCH frame-timing detection, fine carrier-frequency synchronization, and cell-specific scrambling code (CSSC) identification. Simulation demonstrated that this scheme can identify the CSSC with high detection probability while precisely synchronizing the carrier frequency in severe frequency-selective fading channels.

In a wireless OFDM-CDMA system, the data-modulated symbol of each user is spread over multiple subcarriers in the frequency domain using a given spreading code. For the downlink (base-to-mobile) transmissions, a set of orthogonal spreading codes defined in the frequency domain is used so that different users data can be transmitted using the same set of subcarriers. The frequency selectivity of the radio channel produces the orthogonality destruction. There are several frequency equalization combining techniques to restore orthogonality, i.e., orthogonal restoration combining (ORC), control equalization combining (CEC) that is a variant of ORC, threshold detection combining (TDC), and minimum mean square error combining (MMSEC). The ORC can restore orthogonality among users but produces noise enhancement. However, CEC, TDC, and MMSEC can balance the orthogonality restoration and the noise enhancement. In this paper, we investigate, by means of computer simulation, how the BER performances achievable with ORC, CEC, TDC, and MMSEC are impacted by the propagation parameters (path time delay difference and fading maximum Doppler frequency), number of users, pilot power used for channel estimation, and channel estimation scheme. To acquire a good understanding of ORC, CEC, TDC, and MMSEC, how they differ with respect to the combining weights is discussed. Also, the downlink transmission performances of DS-CDMA and OFDM-CDMA are compared when the same transmission bandwidth is used. How much better performance is achieved with OFDM-CDMA than with DS-CDMA using ideal rake combining is discussed.

We describe a new automated method for detecting embedded objects in the ultrasonic non-destructive testing (NDT) system. A-scan waves collected by our developed system are converted into a B-scan image. The sensor system has the noise signals independent from targets to be detected. In the ultrasonic NDT system, the signals are due to disturbing of echoes produced by the transducers and multiple reflections. These signals are called inherent wave. This paper first proposes the estimation method of the inherent wave from the B-scan image. After this method subtracts the inherent wave, the resultant image (suppression image) is considered as the image consisting of only echoes from the embedded objects. Second, analysis of the intensity histogram of the suppression image leads the candidate points of embedded objects. Finally, fuzzy if-then rules can represent information on distribution of the intensity histogram and the homogeneous intensity levels of the objects. Evaluated degrees from the inference results can demonstrate the embedded objects. The method was applied to concrete members with reinforcing bars, resin tubes and steel pipes. The experimental results showed that this method was able to automatically detect the embedded objects with high accuracy and to display the location of embedded objects.

We propose and demonstrate a novel method to measure the polarization mode dispersion (PMD) of optical devices. The device under test (DUT) is installed in a fiber laser cavity which can operate at multiwavelength. PMD can be evaluated by the wavelength spacing of the multiwavelength laser output spectrum. In our method, the maximum extrema wavelength is easier to be identified than in the conventional fixed-analyzer (FA) method. We measure the PMD of polarization maintaining fibers (PMFs) and the ITU-T round robin KDD samples.

The purpose of this paper is to derive a novel fractionally spaced Bayesian decision feedback equalizer (FS-BDFE). The oversampling technique changes single input single output (SISO) linear channel to single input multiple output (SIMO) linear channel. The Bayesian decision variable in the FS-BDFE is defined as the product of Bayesian decision variables in the Bayesian decision feedback equalizers (BDFE) corresponding to each channels of the SIMO. It can be shown that the FS-BDFE has less decision error probability than the conventional BDFE. The effectiveness of the proposed equalizer is also demonstrated by the computer simulation.

This paper discusses two types of polyphase sequence sets, which will successfully provide CDMA systems without co-channel interference. One is a type of ZCZ sets, whose periodic auto-correlation functions take zero at continuous shifts on both side of the zero-shift, and periodic cross-ones also take zero at the continuous shifts and the zero-shift. The other is a new type of sets consisting of some subsets of polyphase sequences with zero cross-correlation zone, called ZCCZ sets, whose periodic cross-correlation functions among different subsets have take zero at continuous shifts on both side of the zero-shift including the zero-shift. The former can achieve a mathematical bound, and the latter can have large size.

OFDM transmission performance in mobile communications suffers severe degradation caused by multipath delay difference greater than the Guard Interval (GI). This is because the excess delay results in considerable Inter-Symbol Interference (ISI) between temporally adjacent symbols and Inter-Carrier Interference (ICI) among subcarriers in the same symbol. This paper proposes a robust OFDM receiver for the scattered pilot OFDM signal that can effectively suppress both ISI and ICI by using two types of equalization and a smoothed FFT-window. In order to verify the performance of the proposed receiver, computer simulations are conducted in accordance with the scattered pilot OFDM signal format of the Digital Terrestrial Television Broadcasting (DTTB). The simulation results demonstrate that the proposed receiver shows much better performance than the conventional receiver in multipath fading environments with the delay difference greater than GI duration.

In this paper, we propose and describe a new synchronizer for the FFT timing applicable to multi-carrier spread-spectrum (MC-SS) communication systems. The performance of the synchronizer is evaluated in terms of false- and miss-detection probabilities in the presence of additive white Gaussian noise (AWGN) and Rayleigh fading.

An S-band linearizer was developed using GaAs MMIC technology. We call it the even-order-distortion-implemented intermodulation distortion controller (EODIC). EODIC uses even-order intermodulation distortion (IM) components in the second harmonic frequency band to control its IM components in the fundamental frequency band. EODIC is a suitable tool to compensate near-saturated high power amplifiers (HPAs). We developed an EODIC using MMIC technology. This paper describes the principle of EODIC and then introduces the EODIC MMIC in detail. This paper also presents the IM reduction performance of an EODIC in a near-saturated HPA.

A wireless communications system with a transmission speed of 18 Mbit/s is presented using the 2.4 GHz ISM band. This system employs the Carrier Frequency Offset-Spread Spectrum (CFO-SS) scheme and the Dual-Polarization Staggered Transmission (DPST) scheme. The 18 Mbit/s CFO-SS system (named CFO-SS18) was developed and its performance evaluated in fields. In this paper, the detailed operating principle of CFO-SS and DPST schemes, together with the specifications and structures of CFO-SS18, are presented. Results of indoor and field tests obtained by using CFO-SS18 are also presented.

A new approach to build up a real-time multiprocessing system that is configuration flexible for evaluating space-time (ST) equalizers is described. The core of the system consists of fully programmable devices such as digital signal processors (DSPs), field-programmable gate arrays (FPGAs), and reduced instruction set computers (RISCs) with a real-time operating system (RTOS). The RTOS facilitates flexibility in the multi-processor configuration for the system conforming with ST processing algorithms. Timing jitter synchronization caused by use of the RTOS-embedded system is shown, and an adjustable frame format for a transmission system is described as a measure to avoid the jitter problem. Bit error rate (BER) performances measured in uncorrelated frequency-selective fading channels show that an ST equalizer provides a significantly lower BER than an array processor does.

In this paper, we propose a floorplanning method for VLSI building block layout. The proposed method produces a floorplan under the timing constraint for a given netlist. To evaluate the wiring delay, the proposed method estimates the global routing cost for each net with buffer insertion and wire sizing. The slicing structure is adopted to represent a floorplan, and the Elmore delay model is used to estimate the wiring delay. The proposed method is based on simulated annealing. To shorten the computation time, a table look-up method is adopted to calculate the wiring delay. Experimental results show that the proposed algorithm performs well for producing satisfactory floorplans for industrial data.

This paper discusses a statistical effect of performance optimization to uncertainty in circuit delay. Performance optimization has an effect of balancing the delay of each path in a circuit, i.e. the delay times of long paths are shortened and the delay times of short paths are lengthened. In these path-balanced circuits, the uncertainty in circuit delay, which is caused by delay calculation error, manufacturing variability, fluctuation of operating condition, etc., becomes worse by a statistical characteristic of circuit delay. Thus, a highly-optimized circuit may not satisfy delay constraints. In this paper, we demonstrate some examples that uncertainty in circuit delay is increased by path-balancing, and we then raise a problem that performance optimization increases statistically-distributed circuit delay.

A blind equalizer which uses the differential constant modulus algorithm (DCMA) is introduced. An anchored FIR equalizer applied to a first-order autoregressive channel and updated according to the DCMA is shown to converge to the inverse of that channel regardless of the initial tap-weights and the gain along the direct path.

We propose linearization techniques for MMIC amplifiers. The key points of these techniques are increased linearity of a newly-developed low-distortion MESFET (LD-FET) and maximized IP3 by combining the LD-FET with a high-gain depletion-mode MESFET (D-FET) with no increase in power consumption. The LD-FET is characterized by its unique channel dopant-profile prepared by a buried p-type ion-implantation and double n-type ion-implantations with high- and low-acceleration energies. This FET achieves flatter behavior in terms of mutual conductance (gm) compared with conventional MESFETs irrespective of changes in the gate bias voltage (Vgs). A self-alignment/selective ion-implantation process enables the LD-FET and D-FET to be fabricated simultaneously. This process encourages IP3 maximization of the multi-stage amplifier by appropriately combining the advantages of the two differently characterized MESFETs. We fabricated and tested a highly linearized two-stage MMIC amplifier utilizing the proposed techniques, and found that its third-order intermodulation ratio (IMR) performance was 8.7 dB better than that of conventional MMIC amplifiers at an input signal level of -20 dBm with no increase in current dissipation. The configuration constructed by using the proposed techniques equivalently reduces the current dissipation of the second stage to 1/2.72 times that of the conventional configuration, which requires a 2.72 times larger D-FET at the second stage to obtain an 8.7-dB IMR improvement. Furthermore, we were able to improve the IMR by 3.5 dB by optimizing the gate bias conditions for the LD-FET. These results confirm the validity of the proposed techniques.

In ATM networks, call processing on switches can be greatly simplified by using the concept of virtual path (VP); and good resource management strategies ensure that virtual channel connections (VCC) can be rapidly and efficiently established. In order to have good system performance, several methods of constructing virtual paths and strategies of allocating and managing resources should be considered. In this paper, several multicast strategies with dynamic routing are used and applied to the metropolitan LATA network. For the VP-based network, dynamic routing is also applied, and those strategies are discussed and investigated to show the versatility of the approach. Some results using dynamic multicast routing, such as call blocking rate, VP utilization, and VP adjustment rate, are obtained for the different strategies by simulation experiments.

In this paper, a new approach is proposed to improve the channel estimation accuracy with channel tracking capability for adaptive multicarrier equalization systems under time-variant multipath fading channel. The improvement is carried out based on the assumption that the channel is static over a transmitted block period, and slowly linearly changing over several block periods. By applying IFFT to the concatenated channel transfer function derived from different blocks, the noise-averaging improvement is achieved, and a better estimation of the channel coefficients with some delay can be obtained. A multi-step channel predictor and a smoothing filter is utilized to compensate for the delay and make the system more robust in terms of channel tracking performance. Adaptive time domain equalization is jointly performed with this approach to avoid the channel invertibility problem found in the frequency domain approach. A short period of training sequences is utilized resulting in more efficient use of available communication capacity. The effectiveness of the proposed approach is evaluated through simulation for multicarrier systems in time-variant multipath fading channels. Results show improvement over previous channel estimation schemes.

Scanning near-field optical microscopy (SNOM) combined with Kelvin force microscopy (KFM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film as an integrated deflection sensor have been developed. We applied the frequency modulation (FM) detection method to this setup to increase the detection sensitivity of electrostatic forces between a probe tip and a sample. Latex particles dispersed in a polyvinylalcohol (PVA) thin film deposited onto a glass substrate were stably imaged with the SNOM while both local optical and electrical properties of a ferroelectric thin film were successfully investigated.

When we use an adaptive array antenna (AAA) with the minimum mean square error (MMSE) criterion under the multipath environment, where the receiving signal level varies, it is difficult for the AAA to converge because of the distortion of the desired wave. Then, we need the equalization both in space and time domains. A tapped-delay-line adaptive array antenna (TDL-AAA) and the AAA with linear equalizer (AAA-LE) have been proposed as simple space-temporal equalization. The AAA-LE has not utilized the recursive least square (RLS) algorithm. In this paper, we propose a space-temporal simultaneous processing equalizer (ST-SPE) that is an AAA-LE with the RLS algorithm. We proposed that the first tap weight of the LE should be fixed and the necessity of that is derived from a normal equation in the MMSE criterion. We achieved the space-temporal simultaneous equalization with the RLS algorithm by this configuration. The ST-SPE can reduce the computational complexity of the space-temporal joint equalization in comparison to the TDL-AAA, when the ST-SPE has almost the same performance as the TDL-AAA in multipath environment with minimum phase condition such as appeared at line-of-sight (LOS).

In this paper, we analyze the convergence and steady-state behavior of the least mean-square (LMS) adaptive filtering algorithm for a finite-length phase-splitting hybrid-type decision feedback equalizer (H-DFE). With some approximations, we derive an iterative expression for the excess mean-square error (MSE) of the H-DFE, which is composed of three statistically dependent excess MSEs; that is, the excess MSEs of the feedforward filter (FFF), intersymbol interference predictive feedback filter (ISI-FBF), and noise predictive feedback filter (NP-FBF) taps. Computer simulation and analytical results show that the average eigenvalue of the input signal for the NP-FBF taps of the H-DFE is time-varying, whereas those for the FFF and ISI-FBF taps are fixed. Nevertheless, the H-DFE can be implemented with fixed step sizes that ensure the convergence of the LMS algorithm without performance degradation from the standpoint of convergence speed, as well as steady-state performance for digital subscriber line (xDSL) applications.