This paper proposes a radio repeater, cell enhancer (CE), that targets 5-GHz broadband wireless access systems to improve the coverage probability without the need to establish a new access point (AP). The CE adopts a non-regenerative repeating scheme to transfer signals and implements two novel approaches, timing control and gain control, to apply to the target systems. By monitoring the control signals broadcast from the AP, the CE behaves as an AP using the same frame timing and transmitting power level, but using a second frequency channel. Thus, the CE can extend the coverage area of one AP. It appears that, however, in the orthogonal frequency division multiplexing (OFDM) system, over two hops with non-regenerative repeating, the additive effect of multipath fading from the two paths results in more violent subcarrier fluctuations and increased delay spread. Computer simulations in multipath fading environments derive the required CNR values for each path, which are required when the CE is installed in the field. In addition, we clarify that multiple CEs can use the same second frequency and provide better coverage with useful macro diversity gain in 5-GHz indoor environments.

This paper considers combining receptions with multiple receive antennas for space time coded MPSK signals over correlated Rayleigh fading channels. For the system with dual-antenna at receiver, a new transform is proposed, which can convert the correlated fading signals into uncorrelated ones. With the results obtained by using the proposed transform, the equivalent selective combining (SC) reception and maximum likelihood (ML) reception are presented. Theoretical analysis shows that ML reception has better performance than SC reception in terms of bit error rate. For the system with triple antenna at receiver, the simulation results are presented by using Monte Carlo method. All the results show that compared to using a receive antenna, a considerable signal to noise ratio gain can be obtained by using multiple receive antennas when the correlation coefficients among the receive antennas is not too high.

This paper presents a new decoupling circuit for suppressing radiated emissions due to power plane resonance in multilayer printed circuit boards (PCBs). This circuit is based on transmission line theory, and consists of two decoupling capacitors and one power trace. The two capacitors, one mounted on the power pin of an IC and the other mounted on the common power distribution bus in a board, are connected through the power trace. The characteristic impedance of the trace is much higher than the impedance of the capacitors. In addition, the length of the trace between the capacitors is less than 1/4 the effective wavelength for high frequency (e.g., 1 GHz). Tests we performed on simple PCBs confirm that our decoupling circuit suppresses radiated emissions due to power plane resonance.

It is known that MUSIC and ESPRIT algorithms can estimate simultaneously both the instantaneous Direction of Arrival (DOA) and the instantaneous Angular Spread (AS) in multiple scattering environments. These algorithms use the Extended Array Mode Vector (EAMV) with complex angle. The previous work evaluated the performance of those algorithms by comparing the estimated DOA and the estimated AS with the DOA and the AS given in the EAMV, which uses the first-order approximation. Thus, this evaluation method has not clearly reflected the estimation accuracy of MUSIC and ESPRIT. This paper presents the joint estimation performance of MUSIC and ESPRIT by introducing the criteria for evaluation. For this, the spatial signature (SS) is reconstructed from the estimates of the DOA and the AS, and compared to the true SS in the meaning of data fitting.

A novel power spectral density accumulation (PSDA) method for estimating the bandwidth of the clutter spectra is proposed, based on a priori knowledge of the shape of the clutter spectra. The comparison of the complexity and the performance between the PSDA method and the general ones is presented. It is shown that the PSDA method is effective for the short-time clutter data in the practical application.

We propose a subchannel power control scheme in the OFDM system, which transmits data with a variable power level for each subchannel based on the received SNR. The OFDM system, employing the D-QPSK modulation and the proposed subchannel power control with a grouping coefficient equal to 3, gives about 2.3 dB gain in Eb/N0 comparing with the conventional OFDM system, under the two-ray multipath channel with the mean value of the second-ray's attenuation coefficient equal to 0.25, for the required BER equal to 10-5.

A lithium-ion (Li-ion) battery protection IC with an average current of 0.99 µA (at a battery voltage of 3.6 V) and a standby current (after detecting over-discharge) less than 0.01 µA is presented. This low power performance is achieved via a power-on duty-cycle technique. The protection circuit samples the voltage of the battery periodically and powers down during the rest of time. This Li-ion battery protector provides over-charge, over-discharge, excess-current and short circuits protection. This protection IC was implemented in a 0.6-µm CMOS technology and the active area is 880 µm 780 µm.

A VLSI algorithm for division in GF(2m) with the canonical basis representation is proposed. It is based on the extended Binary GCD algorithm for GF(2m), and performs division through iteration of simple operations, such as shifts and bitwise exclusive-OR operations. A divider in GF(2m) based on the algorithm has a linear array structure with a bit-slice feature and carries out division in 2m clock cycles. The amount of hardware of the divider is proportional to m and the depth is a constant independent of m.

Precise interconnect analysis is strongly required for giga-scale integration the operation frequency of which is excess 10 GHz. In this study, detailed and accurate analyses of a coaxial interconnect and an actual rectangular interconnect have been performed by the direct evaluation of Maxwell's equations and the finite element method, respectively. It has been revealed that there are two propagation modes for LSI interconnects: skin depth limited propagation mode and interconnect induced slow wave mode. In a miniaturized interconnect, the propagation mode is the interconnect induced slow wave mode; therefore, we cannot obtain the light-speed propagation due to such an interconnect-induced effect. In order to overcome this speed limitation or to improve signal integrity, it is essential to introduce a short interconnect for a miniaturized structure, and a much larger interconnect than the skin depth. We propose a gas-isolated interconnect as a candidate for an ultimately low-k structure in order to increase the signal-propagation speed. By the introduction of such structures, the performance of miniaturized devices in the deep submicron region will be effectively enhanced.

A parallel file system is normally used to support excessive file requests from parallel applications in a cluster system, whereas prefetching is useful for improving the file system performance. This paper proposes dynamic file prefetching scheme based on file access patterns, named table-comparison prefetching policy, that is particularly suitable for parallel scientific applications and multimedia web services in a VIA-based parallel file system. VIA relieves the communication overhead of traditional communication protocols, such as TCP/IP. The proposed policy introduces a table-comparison method to predict data for prefetching. In addition, it includes an algorithm to determine whether and when prefetching is performed using the current available I/O bandwidth. Experimental results confirmed that the use of the proposed prefetching policy in a VIA-based parallel file system produced a higher file system performance for various file access patterns.

Properly representation of the complexity of class structure will be useful in object oriented software developments. Although some class complexity metrics have been proposed, they have ignored directions of coupling relationships among methods and attributes, such as whether a method writes data onto an attribute or reads data from the attribute. In this paper, we use a directed graph model to represent such coupling relationships. Based on the directed graph model, we propose a metric of class structural complexity. The proposed metric satisfies necessary conditions of complexity metric suggested by Briand and others. The following fact is showed by experimental data of Java classes. While the proposed metric follows a conventional metric, the proposed metric can capture an aspect of class structural complexity which is lost by the conventional one.

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.

In this paper, new integrated schemes of scheduling real-time traffic and cell loss control in high speed ATM networks are proposed for multiple priorities based on variable queue length thresholds for scheduling and the Partial Buffer Sharing policy for cell loss control. In our schemes, the queues for buffering arriving cells can be constructed in two ways: one individual queue for each user connection, or one physical queue for all user connections. The proposed schemes are considered to provide guaranteed QoS for each connection and cell sequence integrity for virtual channel/path characteristics. Moreover, these new schemes are quite flexible and can realize different scheduling algorithms. This paper also provides the Stochastic Petri Net models of these integrated schemes and an approximate analysis technique, which significantly reduces the complexity of the model solution and can be applied to real ATM switch models. From the numerical results, we can see that our schemes outperform those well-known schemes such as the head-of-line (HOL) priority control and the queue length threshold (QLT) policy.

We propose a set of Fabry-Perot etalons integrated in a planar lightwave circuit (PLC-FPE) designed for a unified system for broadcasting and communication. A PLC-FPE containing four etalons having different cavity lengths is fabricated and their loss and frequency characteristics are investigated. The total loss and the maximum finesse were found to be 8 dB and 34, respectively.

Due to large capacitance, high access ratio and wide access bitwidth, frame memory is one of the most energy consuming devices in modern video encoders. This paper proposes a new architectural technique to reduce energy dissipation of frame memory through adaptive bitwith compression. Unlike related approaches, the technique utilizes the fixed order of memory accesses and data correlation of video sequences, by dynamically adjusting the memory bitwidth to the number of bits changed per pixel. Instead of treating the data bits independently, we group the most significant bits together, activating the corresponding group of bit-lines adaptively to data variation. The approach is not restricted to the specific bit-patterns nor depends on the storage phase. It works equally well on read and write accesses, as well as during precharging. Simulations show that using this method we can reduce the total energy consumption of the frame memory cell array by 20% without affecting the picture quality. The implementation scheme is simple yet compact.

In this paper, a CMOS data recovery PLL for DVD-ROM is described. Some techniques have been introduced to alleviate the specifications required to analog circuits. A new phase detector alleviates the timing specification of a delay line and a pulse generator. A new frequency detector increases the capture range up to 8% of the center frequency. We have achieved to realize the data recovery PLL that operates at DVD-ROMx14 speed.

A new method of error concealment for MPEG videos, in which motion vectors are hidden in an MPEG bitstream as a watermark, is proposed in this paper. Several conventional methods conceal error regions by using motion vectors, which are re-estimated in a decoding process. These methods, however, have two problems: (1) The accuracy of a re-estimated motion vector is lower than that of an estimated motion vector in an encoding process. (2) A large amount of calculation is required to re-estimate motion vectors. The proposed method overcomes these problems by using hidden accurate motion vectors. That is, it hides several bits in each 88 DCT block of all frames and, simultaneously, inhibits the image degradation caused by hiding motion vectors. In addition, it has upward compatibility with a standard MPEG decoder and can be combined with conventional methods. Simulation results show that the accuracy of error concealment by the new method is higher than that of the conventional methods.

In this paper, we propose the multirate repeating method for alias free subband adaptive filters (AFSAFs) and consider its convergence property. It is shown that we can adjust the convergence speed and the final error of the adaptive filters by varying its two parameters according to the requirements of the applications where the method is applied. The proposed method has two parameters, namely, the number of channel and the number of repetition. We show that by increasing the number of channels we can reduce the final error, and this property is preferred when the signal-to-noise ratio (SNR) is low. On the other hand, we show that the convergence speed of the AFSAF approaches to that of the affine projection algorithm (APA) by increasing the number of repetition. Through the computer simulations, we show the effect of the proposed method.

The reverse link bandwidth efficiency of a spectrally overlapped CDMA system with fast transmit power control is evaluated to find the optimum overlapping, where the bandwidth efficiency is defined as the maximum aggregate bit rate of all subsystems per unit bandwidth (bps/Hz). Single and multiple cell environments are considered. Besides the rectangular chip pulse, the impact of a pulse-shaping filter is discussed. It is found that the raised cosine spectrum pulse shaping helps to increase the bandwidth efficiency and strict pulse shaping filter problem can be avoided if a large number of subsystems are overlapped. It is also found that the optimum carrier spacing remains unchanged irrespective of the power delay profile shape of the multipath channel, whether multipath fading exists or not, and whether a single cell or multiple cell system is considered. However, the bandwidth efficiency strongly depends on them and the impacts of the related parameters are discussed.

In this paper, a low-cost radio-on-fiber (ROF) system for a 36 GHz band road-vehicle communication system (RVCS) is proposed and demonstrated. Optical components for 10 Gb/s baseband transmission systems, which are becoming lower in cost, are used for the proposed system. The signal is transmitted in the optical link in the form of an intermediate frequency (IF) signal of the 5.8 GHz band. The third subharmonic of a local oscillator wave (LO) is transmitted simultaneously with the IF signal from the central station to the remote stations (RSs). This scheme enables the realization of RSs without costly millimeter-wave synthesizers. In such a configuration, the influence of intermodulation distortion between the IF signal and the LO subharmonic and degradation of the carrier-to-noise ratio (CNR) could possibly be a problem, and so an analysis and experiments were carried. It was clarified that the compression of dynamic range caused by the simultaneous transmission was small. Frequency tripling of the LO degraded the CNR of the LO; however, this effect was compensated for by increasing the optical modulation index (OMI) of the LO subharmonic. Increasing the OMI of the LO subharmonic proved to have no influence on the IM3 characteristics of the RF signal analytically and experimentally. The proposed low-cost system proved to have sufficient characteristics for millimeter-wave RVCS.