This paper discusses performance limitation of on-chip interconnects. On-chip global interconnects are considered to be a bottleneck of high-performance LSIs. To overcome this issue, high-speed signaling and large throughput interconnection using electrical wires have been studied. However the limitation of on-chip interconnects has not been examined sufficiently. This paper reveals the maximum performance of on-chip global interconnects based on derived analytic expressions and detailed circuit simulation. We derive trade-off curves among bit rate, interconnect length, and eye opening both for single-end and for differential signaling. The results show that differential signaling improves signaling performance several times compared with conventional single-end signaling, and demonstrate that 80 Gbps differential signaling on 10 mm interconnects is promising.

Holey Fiber (HF) technology has progressed rapidly in recent years and has resulted in the development of a wide range of optical fibers with unique and highly useful optical properties including endlessly single-mode guidance, and high optical nonlinearity. In this paper the state-of-the-art HF technology for all-optical signal processing devices is reviewed from a perspective of possible application for telecommunications.

This paper describes a new multi-channel method of noisy speech recognition, which estimates the log spectrum of speech at a close-talking microphone based on the multiple regression of the log spectra (MRLS) of noisy signals captured by distributed microphones. The advantages of the proposed method are as follows: 1) The method does not require a sensitive geometric layout, calibration of the sensors nor additional pre-processing for tracking the speech source; 2) System works in very small computation amounts; and 3) Regression weights can be statistically optimized over the given training data. Once the optimal regression weights are obtained by regression learning, they can be utilized to generate the estimated log spectrum in the recognition phase, where the speech of close-talking is no longer required. The performance of the proposed method is illustrated by speech recognition of real in-car dialogue data. In comparison to the nearest distant microphone and multi-microphone adaptive beamformer, the proposed approach obtains relative word error rate (WER) reductions of 9.8% and 3.6%, respectively.

This paper presents a method of searching for the shortest route via the most designated points with the length not exceeding the preset upper bound. The proposed algorithm can obtain the quasi-optimum route efficiently and its effectiveness is verified by applying the algorithm to the actual map data.

Digital signature is by far one of the most important cryptographic techniques used in the e-government and e-commerce applications. It provides authentication of senders or receivers and offers non-repudiation of transmission (senders cannot deny their digital signature in the signed documents and the document cannot be altered in transmission without being detected). This paper presents our implementation results of digital signature algorithms on IC cards by using byte-unit modular arithmetic algorithm method. We evaluated the performance of well-known ESIGN and RSA digital signature algorithms on the dedicated IC card chips and showed that ESIGN is more efficient than RSA.

In this paper, we propose an adaptive algorithm based on accumulated signal processing, which could be applicable to Post-FFT-type OFDM adaptive array antennas. Proposed scheme calculates the weight of each element at a particular instant t, by considering both post- and pre-received symbols. Because of the use of additional forthcoming information on channel behavior in the weight calculation scheme, one can expect an improved performance in fast fading conditions by using the proposed adaptive algorithm. This paper also discusses the application of the proposed adaptive algorithm to OFDM adaptive array. In OFDM application, a few subchannels are being used to transmit pilot symbols, and at the receiver, the proposed adaptive algorithm is applied to those pilot subchannels, and interpolates the weights for the data subchannels which are allocated between the pilot subchannels. Finally, the system performance improvement with the application of the proposed adaptive algorithm is verified by computer simulation.

This paper proposes a rail-to-rail OTA. By adding a signal decomposing circuit at the input of given OTAs that have a limited input voltage range, a rail-to-rail OTA is obtained. Each decomposed input voltage signal is converted to a current signal by an OTA and each output current of OTAs is summed to obtain a linear output signal. Since the input signal is decomposed into small magnitude voltage signals, the OTAs used to the voltage-current conversion do not require a wide input-range and any OTA can be used to realize a rail-to-rail input voltage range OTA. HSPICE simulations are performed to verify the validity of the proposed method.

The facility layout problem is one of the most fundamental quadratic assignment problems in operations research. In this paper, we present an improved genetic algorithm for solving the facility layout problem. In our computational model, we propose several improvements to the basic genetic procedures including conditional crossover and mutation. The performance of the proposed method is evaluated on some benchmark problems. Computational results showed that the improved genetic algorithm is capable of producing high-quality solutions.

In this letter, we evaluate the performance of Optical Cross Connect (OXC) architectures equipped with limited-range wavelength converters. Performance will be evaluated according to both an optimum and a random output wavelength assignment strategy. Analytical and simulation results show the possibility to reduce the conversion degree of the Wavelength Converters while keeping network performance high.

A design optimization of active shield circuit using noise averaging method is proposed. The relation between the averaged noise and the design parameters of the active shield circuit such as circuit gain and on-chip layout is examined. A simple design guideline is also provided. Simulation results show that the active shield circuit designed by the proposed optimization method gives a better noise suppression performance of about 28% than the conventional one.

An active shield circuit which effectively reduces the substrate noise on the entire area inside the guard ring regardless of the noise source position is proposed. Simulation result shows that the proposed circuit can reduce the noise level to -85 dB while a conventional guard ring gives -52 dB.

Bandpass sampling algorithm is effectively adopted to obtain the digital signal with significantly reduced sampling rate for a single radio frequency(RF) signal. In order to apply the concept to multiple RF signals, we propose bandpass sampling algorithms with the normal and the inverse placements since we are interested in uniform order of the spectrum in digital domain after bandpass sampling. In addition, we verify the propose algorithms with generalized equation forms for the multiple RF signals.

This paper proposes the optimum design for adaptively controlling the spreading factor in Orthogonal Frequency and Code Division Multiplexing (OFCDM) with two-dimensional spreading according to the cell configuration, channel load, and propagation channel conditions, assuming the adaptive modulation and channel coding (AMC) scheme employing QPSK and 16QAM data modulation. Furthermore, we propose a two-dimensional orthogonal channelization code assignment scheme to achieve skillfully orthogonal multiplexing of multiple physical channels. We first demonstrate the reduction effect of inter-code interference by the proposed two-dimensional orthogonal channelization code assignment. Then, computer simulation results show that in time domain spreading, the optimum spreading factor, except for an extremely high mobility case such as for the fading maximum Doppler frequency of fD = 1500 Hz, becomes SFTime = 16. Furthermore, it should be decreased to SFTime = 8 for such a very fast fading environment using 16QAM data modulation. We also clarify when the channel load is light such as Cmux/SF = 0.25 (Cmux and SF denote the number of multiplexed codes and total spreading factor, respectively), the required average received signal energy per symbol-to-noise power spectrum density ratio (Es/N0) is reduced as the spreading factor in the frequency domain is increased up to say SFFreq = 32 for QPSK and 16QAM data modulation. When the channel load is close to full such as when Cmux/SF = 0.94, the optimum spreading factor in the frequency domain is SFFreq = 1 for 16QAM data modulation and SFFreq = 1 to 8 for QPSK data modulation according to the delay spread. Consequently, by setting several combinations of spreading factors in the time and frequency domains, the near maximum link capacity is achieved both in cellular and hotspot cell configurations assuming various channel conditions.

Video telephone service (VTS) is considered one of promising services provided in wideband CDMA (WCDMA) networks. Without a designated call admission policy, VTS calls are expected to suffer from relatively high probability of blocking since they normally have more stringent signal quality requirement than ordinary voice calls. In this letter, we consider a prioritized call admission design in order to reduce the blocking probability of VTS calls, which may encourage the users to access the newly-provided VTS in a more comfortable way. The VTS calls are given a priority by reserving a number of channel-processing equipments. With the reservation, the blocking probability of prioritized VTS calls can be reduced evidently. That of ordinary calls, however, is increasing instead. This letter provides a system model that counts the blocking probabilities of VTS and ordinary calls simultaneously, and numerically examines an adequate level of the prioritization for VTS calls. The results show that the prioritization level should be selected depending on received interference as well as bandwidth required for VTS.

This paper presents the selective orthogonal matrix least-squares (SOM-LS) method for representing a multiport network characterized by sampled data with the rational matrix, improving the previous works, and providing new criteria. Recently, it is needed in a circuit design to evaluate physical effects of interconnects and package, and the evaluation is done by numerical electromagnetic analysis or measurement by network analyzer. Here, the SOM-LS method with the criteria will play an important role for generating the macromodels of interconnects and package in circuit simulation level. The accuracy of the macromodels is predictable and controllable, that is, the SOM-LS method fits the rational matrix to the sampled data, selecting the dominant poles of the rational matrix. In examples, simple PCB models are analyzed, where the rational matrices are described by Verilog-A, and some simulations are carried out on a commercial circuit simulator.

SFLASH was chosen as one of the final selection of the NESSIE project in 2003. It is one of the most efficient digital signature scheme and is suitable for implementation on memory-constrained devices such as smartcards. Side channel attacks (SCA) are a serious threat to memory-constrained devices. If the implementation on them is careless, the secret key may be revealed. In this paper, we experimentally analyze the effectiveness of a side channel attack on SFLASH. There are two different secret keys for SFLASH, namely the proper secret key (s,t) and the random seed Δ used for the hash function SHA-1. Whereas many papers discussed the security of (s,t), little is known about that of Δ. Steinwandt et al. proposed a theoretical DPA for finding Δ by observing the XOR operations. We propose another DPA on Δ using the addition operation modulo 232, and present an experimental result of the DPA. After obtaining the secret key Δ, the underlying problem of SFLASH can be reduced to the C* problem broken by Patarin. From our simulation, about 1408 pairs of messages and signatures are needed to break SFLASH. Consequently, SHA-1 must be carefully implemented in order to resist SCA on SFLASH.

The traffic congestion problem in urban areas is worsening since traditional traffic signal control systems cannot provide] efficient traffic regulation. Therefore, dynamic traffic signal control in Intelligent Transportation System (ITS) recently has received increasing attention. This study devised a multi-agent architecture, the Adaptive and Cooperative Traffic light Agent Model (ACTAM), for a decentralized traffic signal control system. The proposed architecture comprises a data storage and communication layer, a traffic regulation factor processing layer, and a decision-making layer. This study focused on utilizing the cooperation of multi-agents and the prediction mechanism of our architecture, the Forecast Module, to forecast future traffic volume in each individual intersection. The Forecast Module is designed to forecast traffic volume in an intersection via multi-agent cooperation by exchanging traffic volume information for adjacent intersections, since vehicles passing through nearby intersections were believed to significantly influence the traffic volume of specific intersections. The proposed architecture can achieve dynamic traffic signal control. Thus, total delay time of the traffic network under ACTAM can be reduced by 37% compared to the conventional fixed sequence traffic signal control strategy. Consequently, traffic congestion in urban areas can be alleviated by adopting ACTAM.

The number of satisfying assignments of k-CNF formulas is computed using the inclusion-exclusion formula for sets of clauses. Recently, it was shown that the information on the sets of clauses of size log k + 2 already uniquely determines the number of satisfying assignments of k-CNF formulas. The proof was, however, only existential and no explicit procedure was presented. In this paper, we show that such a procedure exists.

The PayWord Scheme, invented by Rivest and Shamir, is an efficient micropayment scheme utilizing a hash function. We point out that the scheme has the following problem: a malicious customer can damage the bank by purchasing in excess of the customer's credit which the bank has guaranteed by issuing a certificate. Generally, there are two positions of the bank with regard to the certificate. Position 1: the bank takes full responsibility for the certificate and compensates all payments created by the customer's purchases; and Position 2: the bank does not redeem payments exceeding a limit set for the customer and shares the loss with the shop if trouble occurs. In the PayWord Scheme, the bank can reduce its risk by adopting Position 2 rather than Position 1. However, this paper points out that the bank can damage the shop in Position 2 by impersonating an imaginary customer and making the shop share the loss with the bank. We propose a micropayment scheme (countermeasure) that overcomes these problems.

This paper treats multi-way microstrip power dividers composed of multi-step, multi-furcation, and corners. Since the design procedure is founded on the planar circuit approach in combination with the segmentation method, optimization of the circuit configuration can be performed in a reasonable short computation time when applying the Powell's optimization algorithm. Actually, broadband 3- and 4-way power dividers with mitered bends are designed, and fractional bandwidths of about 90% and 100% are realized for the power-split imbalance less than 0.2 dB and the return loss better than -20 dB, respectively. The validity of the design results is confirmed by an EM-simulator (HFSS) and experiments.