Power-line communication (PLC) systems have been assumed as the systems of low speed and low reliability. The low qualities of the systems, however, are not inherent of PLC but the result of inadequate design strategy of the systems. The systems with proper considerations of the characteristics of power-line as a communication medium achieve reliable high-speed data transmission in power-lines. In fact, the activities on the standardization of high-speed PLC systems have recently started in many countries, and variety of high-speed PLC systems are being to be purchased off-the-shelf. Following this trend of PLC, this manuscript first describes the features of power-line for communications and then explains technical issues on the design of PLC systems of the next generations as the infrastructure of information-communication technology age.

PSK coherent demodulation has difficulty in achieving high speed carrier extraction and symbol synchronization when implementing to slow FH-SS radio system. On the other hand, implementation to FPGA has the requirement of a small gate size to design because of FPGA cost issue. We developed a QPSK coherent demodulation digital modem for FH-SS radio systems using FPGA by solving problems. The designed modem performs symbol synchronization with no carrier extractions, under the limitation of the small gate size requirement. The modem employs shift arithmetic operation and a comb digital BPF to achieve very good synchronization lock-up performance with small gate size. In this paper, the symbol synchronization and the carrier tracking scheme are mainly discussed. Analysis of its performance and stability are also explained. The achievement of its very good performance is presented by experimental measurement.

In this paper, we describe a frame synchronization method for bi-orthogonal modulation systems. In bi-orthogonal modulation systems, several bi-orthogonal sequences are used for data transmission. Frame synchronization in bi-orthogonal modulation systems is difficult because transmitted sequences can change every frame. In the proposed method, each bi-orthogonal sequence consists of two different inner sequences. Each bi-orthogonal sequence has the same arrangement of two different inner sequences. A receiver can track the frame timing by observing the arrangement of inner sequences. In this paper, we analyze the bit error rate performance that takes into account the tracking performance of a system we developed based on our method. The spectral efficiency of the proposed system in code division multiple access (CDMA) systems is also investigated. As a result, we found that the proposed system is effective in synchronous CDMA systems.

In this paper, the sequence interference suppression characteristics of code-diversity DS/CDMA over multipath fading channels are presented. In a code-diversity system, the data signal is modulated with several PN sequences, and using these sequences at the receiver, diversity reception of the signal is carried out to suppress the influence of multiple access interference (MAI) or sequence interference (SI) especially under a near-far problem. First, in a sequence interference and AWGN environment, the basic performance of code-diversity system is presented. Next, in single-path (flat-fading) and multipath fading channels, the average BER performance of the code-diversity system is shown and the observation that the performance of code-diversity system (combined with RAKE reception) is more effective over a multipath fading channel is clarified. Finally, it is presented that by implementing adaptive weight control (AWC) for the code-diversity system over fading channels, the BER performance can further be improved.

This paper proposes iterative demodulation/decoding for parallel combinatorial spread spectrum (PC/SS) systems. A PC/SS system conveys information data by a combination of pre-assigned orthogonal spreading sequences with polarity. In this paper, convolutional coding with a uniform random interleaver is implemented in channel coding, just like as a serial concatenated coding. A 'soft-in/soft-out' PC/SS demodulator based on a posteriori probability algorithm is proposed to perform the iterative demodulation and decoding. Simulation results demonstrate that the proposed iterative demodulation/decoding scheme bring significant improvement in bit error rate performance. This proposed decoding scheme achieves high-speed transmission by two approaches. One is a puncturing operation, and the other is to increase the number of transmitting sequences. In the latter approach, lower error rate performance is achieved comparing with that the punctured convolutional code is used to increase the information bit rate.

This paper investigates the interference suppression effect from much higher rate dedicated physical channels (DPCHs) of a parallel-type coherent multistage interference canceller (COMSIC) with iterative channel estimation (ICE) by laboratory experiments in the transmit-power-controlled W-CDMA reverse link. The experimental results elucidate that when two interfering DPCHs exist with the spreading factor (SF) of 8 and with the ratio of the target signal energy per bit-to-interference power spectrum density ratio (E_b/I₀) of fast transmit power control, Δ_Eb/I0, of -6 dB (which corresponds to 64 simultaneous DPCHs with SF = 64, i.e., the same symbol rate as the desired DPCH), the implemented COMSIC receiver with ICE exhibits a significant decrease in the required transmit signal energy per bit-to-background noise power spectrum density ratio (E_b/N₀) at the average bit error rate (BER) of 10^-3 (while the matched filter (MF)-based Rake receiver could not realize the average BER of 10^-3 due to severe multiple access interference (MAI)). It is also found that the achieved BER performance at the average BER of 10^-3 of the COMSIC receiver with the A/D converter quantization of 8 bits in the laboratory experiments is degraded by approximately 1.0 dB and 4.0 dB compared to the computer simulation results, when Δ_Eb/I0=-6 dB and -9 dB, respectively, due to the quantization error of the desired signal and path search error for the Rake combiner. Finally, we show that the required transmit E_b/N₀ at the average BER of 10^-3 of the third-stage COMSIC with ICE is decreased by approximately 0.3 and 0.5 dB compared to that of COMSIC with decision-feedback type channel estimation (DFCE) with and without antenna diversity reception, respectively.

This paper evaluates the effect of inter-sector diversity with maximal ratio combining (MRC) coupled with coherent Rake combining and 2-branch antenna diversity reception in the transmit-power-controlled wideband direct sequence code division multiple access (W-CDMA) reverse link. We first elucidate based on laboratory experiments that the required average transmit signal energy per bit-to-background noise spectrum density ratio (E_b/N₀) at the average bit error rate (BER) of 10^-3 with inter-sector diversity using two sectors is decreased by approximately 1.4, 1.0, and 0.2 dB compared to that with inter-cell site diversity using two cell sites with antenna diversity reception due to the superiority of MRC to selection combining (SC), when the difference in the average path loss between a base station (BS) and a mobile station (MS) is Δ₁₂ = 0, 3, and 6 dB, respectively. We also clarify in actual field experiments that the inter-sector diversity associated with Rake time diversity and antenna diversity further decreases the required average transmit power of a MS if the number of resolved paths is small such as 1 or 2 in each sector reception, even when the fading correlation between sectors is relatively large. Furthermore, we show that the required average transmit power of a MS for satisfying the average BER of 10^-3 with inter-sector diversity is decreased above approximately 2.0-2.5 dB compared to that with one-sector reception, owing to the significantly increased inter-sector diversity effect in addition to the Rake time diversity and antenna diversity, when the fading correlation averaged over the measurement course is approximately 0.7.

We analyzed the performance of adaptive array antennas with a RAKE receiver by employing a common correlation matrix of the sample matrix inversion (CCM-SMI) algorithm in a multipath Rayleigh fading environment for W-CDMA reverse link. A common correlation matrix is usually used to provide adaptive weights for multiple users and multiple delay paths and can be used in packet communications transmitted using frame units. The proposed CCM-SMI algorithm had a better BER and SINR for lower computational complexity compared with the conventional SMI algorithm, even when using a RAKE receiver in multipath Rayleigh fading environment.

This paper investigates the optimum transmit-antenna-weight generation method for adaptive antenna array transmit diversity (AAA-TD) in the W-CDMA forward link: AAA-TD with beam and null steering (BNST), AAA-TD with beam steering (BST), or switched beam transmit diversity with fixed weights (SBTD-FW). The achievable BER performance after carrier frequency calibration in the transmit beam pattern is compared among the three methods assuming a different carrier frequency in a 2-GHz band with the carrier separation of 184.5 MHz based on computer simulations. The simulation results show that the achievable BER performance in the forward link using AAA-TD with BNST is almost identical to that using AAA-TD with BST when there are many more interfering users than there are array antennas, except for the special case when a small number of higher rate users exists in the reverse link. This is because by performing carrier frequency calibration, the directions of the beam nulls are shifted from the real directions of arrival (DOAs) of the interfering users. However, we also show that the required transmit E_b/N₀ at the average BER of 10^-3 using AAA-TD with BST is decreased by approximately 1.0 to 1.2 dB compared to that using SBTD-FW with 12 beams.

This paper elucidates through experiments the improvement in the achievable bit error rate (BER) performance when space time transmit diversity (STTD) is applied to the wideband direct sequence code division multiple access (W-CDMA) forward link. First, laboratory experimental results clarify that the received path timing difference of transmitted signals from two antennas, due to the propagation delay, should be within a chip duration of approximately 1/4 and 1/2 with and without fast transmit power control (TPC), respectively, in order to achieve a prominent transmit diversity effect. We show that the required average received signal energy per bit-to-background noise spectrum density (E_b/N₀) at the average BER of 10^-3 using STTD is decreased by approximately 4.2 (1.7) dB compared to the case of single-antenna transmission at the maximum Doppler frequency, f_D, of 5 Hz without (with) antenna diversity reception at a mobile station (MS) due to the increasing randomization effect of burst error. Furthermore, we elucidate that although the gain of STTD in field experiments is decreased compared to that in laboratory experiments, since the degradation in path search accuracy is greater due to the frequently changing delay time of each path in a real multipath-fading channel, the required average received signal energy per bit-to-interference plus background noise power spectrum density ratio (E_b/I₀) at the average BER of 10^-3 with STTD is decreased by approximately 1.3 to 1.5 (0.7 to 1.0) dB without (with) antenna diversity reception when fast TPC is not applied in the forward link. This indicates that STTD is effective for a channel without TPC such as a common control channel in a real multipath-fading channel.

We previously developed a novel transmission power control method for code-division multiple access (CDMA) wireless systems that is suitable for the transmission control protocol (TCP) and constant bit rate (CBR) connections. It allows each mobile terminal to send packets to arbitrary slots without negotiation or the use of the ALOHA protocol. It results in high bandwidth utilization for TCP connections without the need to modify the TCP protocol or use a snoop agent. In this paper, we improve our previously developed power control method so as to adapt itself to distance variations and instantaneous fluctuations in the received power due to fading. We show that the developed method enables efficient bandwidth utilization compared with the conventional power control technique under various conditions.

Recently, code division multiple access scheme with time division duplex (CDMA/TDD) has drawn considerable attention as means to realize efficient wireless multimedia communications system. In this paper, we propose two time slot allocation algorithms for CDMA/TDD systems to efficiently accommodate multimedia traffic. Assuming a practical multiple cell environment and a multimedia service model which consists of several kinds of circuit-switched and packet-switched services with different quality of services (QoSs), we evaluate the average delay (average time from call generation to channel assignment) of the CDMA/TDD system with the proposed algorithms, and compare the performance with that of CDMA with frequency division duplex (CDMA/FDD) and time division multiple access with TDD (TDMA/TDD) systems. Our computer simulation results show that the CDMA/TDD system with one of the proposed algorithms, which can effectively avoid interference among users with different QoSs, can improve the average delay performance as compared with the other systems.

This paper aims to provide a robust multiuser detection structure that adaptively tracks signature waveform distortion for CDMA multipath signals. In practical wireless environment, multipath fading leads to signature waveform distortion that severely degrades the performance of the linear multiuser detectors (LMDs) designed by exploiting the original signature waveform. In what follows, an iterative algorithm is proposed to track the signature waveform perturbation. The rationale of adaptive processing is based on the subspace method and the Minimum Variance Distortionless Response (MVDR) beamforming concept. Performance evaluation reveals that the proposed adaptive multiuser detection structure reduces the impact of signature waveform perturbation on the performance of the LMDs to a great extent. Moreover, the proposed iterative algorithm is near-far resistant since both the subspace method and the MVDR beamforming technique are energy independent to the interferers.

This paper addresses the problem to extract moving object from the moving background in the mixed domain (MixeD), which makes it possible to carry the filtering in one dimension. Since the velocities of moving object and background are necessary for moving object extraction, we first estimate the velocities based on the appropriate spatial frequency point selection method in the MixeD. Then an optimal filter used for 1-D signal filtering is designed. By filtering 1-D signals over all spatial frequencies, signals with certain velocity vector are extracted, while the extracted image is obtained by applying the 2-D IDFT to the filtered signals. The simulation results show that the method can extract moving object based both on the correctly estimated velocity and the proposed optimal 1-D filter.

In this paper, we propose a frequency domain active noise control (ANC) system without a secondary path model. The proposed system is based on the frequency domain simultaneous perturbation (FDSP) method we have proposed. In this system, the coefficients of the adaptive filter are updated only by error signals. The conventional ANC system using the filtered-x algorithm becomes unstable due to the error between the secondary path, from secondary source to error sensor, and its model. In contrast, the proposed ANC system has the advantage not to use the model. In this paper, we show the principle of the proposed ANC system, and examine its efficiency through computer simulations.

In this study, synchronization phenomena in chaotic oscillators coupled by a transmission line are investigated. In particular investigation using real circuits is done for the first time. It is confirmed that the chaotic subsystems synchronize, although signals propagating along the transmission line are affected by the time delay. Further the period-doubling bifurcation with varying the time delay and anti-phase synchronization phenomena are observed in our circuit model. Also the voltage distribution of transmission line is simulated in order to investigate whether the current flowing through the transmission line is constant or not. It is found that the subsystems synchronize although the current through the transmission line keeps on varying.

This paper describes how the symmetry of a three-phase circuit prevents the symmetric modes of several subharmonic oscillations. First, we make mathematically it clear that the generation of symmetrical 1/3l-subharmonic oscillations (l=1,2,) are impossible in the three-phase circuit. As far as 1/(3l+1)-subharmonic oscillations (l=1,2,) and 1/(3l+2)-subharmonic oscillations (l=0,1,) are concerned, the former in negative-phase sequence and the latter in positive-phase sequence are shown to be impossible. Further, in order to confirm the above results, we apply the method of interval analysis to the circuit equations and obtain all steady state solutions with unsymmetric modes.

The single wire replacement attempts to replace a target wire by another wire without changing the circuit functionality. Due to the large searching space required, there is very little success in directly extending the single wire replacement technique to replace multiple wires at the same time. The objective in this paper is to propose a new logic transformation, called the alternative node (Alnode) technique, which attempts to replace multiple wires at a time. Basically, the transformation simultaneously replaces multiple input wires of a gate by a new set of input wires. To accomplish the transformation, we propose several speedup theorems for replacing multiple wires. In this paper, we also demonstrate that the Alnode technique can be applied to achieve power reduction for domino logic and wire length minimization in layouts. The experimental results are encouraging.

This paper presents an application-specific, heterogeneous multiprocessor synthesis system, named HeMPS, that combines a form of Evolutionary Computation known as Differential Evolution with a scheduling heuristic to search the design space efficiently. We demonstrate the effectiveness of our technique by comparing it to similar existing systems. The proposed strategy is shown to be faster than recent systems on large problems while providing equivalent or improved final solutions.

Let t and n be positive integers. We show that the necessary and sufficient condition for the existence of a balanced t-foil decomposition of the complete graph K_n is n 1 (mod 6t). Decomposition algorithms are also given.

A lower bound for the generalized Hamming weight of linear codes is proposed. The proposed bound is a generalization of the bound we previously presented and gives good estimate for generalized Hamming weight of Reed-Muller, some one point algebraic geometry, and arbitrary cyclic codes. Moreover the proposed bound contains the BCH bound as its special case. The relation between the proposed bound and conventional bounds is also investigated.

This paper introduces fast methods for variable length decoding (VLD) and inverse quantization (IQ) on software MPEG-2 decoders by using Single Instruction stream Multiple Data stream (SIMD) type instructions for multimedia applications. With the VLD implementation, the VLD tables are made as small as possible so as to minimize missed cache accesses, and variable length codewords are decoded concurrently. With the IQ implementation, inverse quantization of the VLD results is performed in parallel. When these methods are used, combined clock cycles for VLD and IQ are roughly 30% shorter than those resulting from conventional methods, and this effect is especially pronounced for high bitrate streams.

Antialiased is one of challenging problems to be solved for the high fidelity image synthesis in 3D graphics. In this paper a rasterization processor which is capable of single-pass full-screen antialiasing is presented. To implement a H/W accelerated single-pass antialiased rasterization processor at the reasonable H/W cost and minimized processing performance degradation, our work is mainly focused on the efficient H/W implementation of a modified version of the A-buffer algorithm. For the efficient handling of partial-pixel fragments of the rasterization phase, a new partial-pixel-merging scheme and a simple and efficient new dynamic memory management scheme are proposed. For the final blending of partial-pixels without loss of generality, a parallel subpixel blender is introduced. To study the feasibility of the proposed rasterization processor as a practical rasterization processor, a prototype processor has been designed using a 0.35 µm EML technology. It operates 100 MHz @3.3 V and has the rendering performance from 25M to 80M pixel-fragments/sec depending on the scene complexity.

In this paper, a discrete-time convergence theorem for continuous-state Hopfield networks with self-interaction neurons is proposed. This theorem differs from the previous work by Wang in that the original updating rule is maintained while the network is still guaranteed to monotonically decrease to a stable state. The relationship between the parameters in a typical class of energy functions is also investigated, and consequently a "guided trial-and-error" technique is proposed to determine the parameter values. The third problem discussed in this paper is the post-processing of outputs, which turns out to be rather important even though it never attracts enough attention. The effectiveness of all the theorems and post-processing methods proposed in this paper is demonstrated by a large number of computer simulations on the assignment problem and the N-queen problem of different sizes.

Phase-based methods for estimating the frequency of a sinusoid have typically suffered from a threshold effect, where for signal to noise ratio (SNR) below the threshold, the mean squared error of the estimate rapidly increases. Furthermore, it is a significant problem that the threshold is considerably high and strongly depends on frequency. To overcome the difficulties, a Kalman-based sinusoidal estimator bank (KSEB) is proposed. In the derivation of the KSEB, a four-channel filter bank and decimation technique are effectively used. The computer simulation also demonstrates the superiority of the KSEB to the other frequency estimators.

This report describes a new methodology for the optimal placement of decoupling capacitors on the printed circuit board (PCB). This method searches the optimal position of decoupling capacitor so that the impedance characteristics at the power supply is minimized in the specified frequency range. In this method, the PCB is modeled by the PEEC method to handle the 3-dimensional structures and Krylov-subspace technique is applied to obtain efficiently the impedance characteristics in the frequency domain.

The implementation of conventional Multi-Code Code Division Multiple Access (MC-CDMA) system needs many orthogonal codes (OCs) compared to traditional Direct Sequence-CDMA (DS-CDMA) systems. To reduce the number of OCs in MC-CDMA for multi-media services, we propose a new scheme in which a sub-orthogonal code (SOC) technique is adopted. To clarify the validity of our proposed system, the computational simulations have performed.