We calculated the shielding characteristic of a three-dimensional array of strip conductors by using the electric field integral equation method and its expansion to an array structure. From reflection coefficients, the effective permittivity of the array is calculated. The effective permittivity becomes negative in the frequency range above resonance, in which the electromagnetic waves travel through the material in an evanescent mode and the transmission coefficient becomes very small.

Information transmission among biological neurons is carried out by a complex series of spike signals. The input inter-spike arrival times at a neuron are believed to carry information which the neurons utilize to carry out a task. In this paper, a new scheme which utilizes the input inter-spike intervals (ISI) for decoding an input spike train is proposed. A spike train consists of a sequence on input spikes with various inter-spike times. This decoding scheme can also be used for neurons which have multiple synaptic inputs but for which each synapse receives a single spike within one input time window. The ISI decoding neural network requires only a few neurons. Example applications show the usefulness of the decoding scheme.

In this paper, we propose a novel array antenna-assisted adaptive modulation scheme for fast fading environments. Although adaptive modulation is an efficient technique capable of establishing high bit-rate digital transmission in a multi-path fading environment, it is sensitive to the fast time variation of the channel because of difficulties in tracking the channel state. To resolve this problem, an array antenna-based Doppler spread compensator was applied to the adaptive modulation scheme. Computer simulation results indicated that the proposed scheme can markedly improve the bit error rate and throughput performance for the region in which the maximum Doppler frequency normalized by the packet length is up to 0.1.

The optimal design of complex infinite impulse response (IIR) two-channel quadrature mirror filter (QMF) banks with equiripple frequency response is considered. The design problem is appropriately formulated to result in a simple optimization problem. Therefore, based on a variant of Karmarkar's algorithm, we can efficiently solve the optimization problem through a frequency sampling and iterative approximation method to find the complex coefficients for the IIR QMFs. The effectiveness of the proposed technique is to form an appropriate Chebyshev approximation of a desired response and then find its solution from a linear subspace in several iterations. Finally, simulation results are presented for illustration and comparison.

Traditional network-level Quality of Service (QoS) techniques are efficient from a network perspective, but they have not provided end-to-end QoS that is satisfactory to users. In this letter, a Coordinated Packet Discard scheme for the distribution of end-to-end QoS requirements into local loss constraints, as well as provision of local loss assurance is proposed. Experiments demonstrate its advantages on increasing QoS-satisfied user ratio and improving network efficiency.

A new method for logical structure analysis of document images is proposed in this paper as the basis for a document reader which can extract logical information from various printed documents. The proposed system consists of five basic modules: text line classification, object recognition, object segmentation, object grouping, and object modification. Emergent computation, which is a key concept of artificial life, is adopted for the cooperative interaction among modules in the system in order to achieve effective and flexible behavior of the whole system. It has three principal advantages over other methods: adaptive system configuration for various and complex logical structures, robust document analysis tolerant of erroneous feature detection, and feedback of high-level logical information to the low-level physical process for accurate analysis. Experimental results obtained for 150 documents show that the method is adaptable, robust, and effective for various document structures.

The site attenuation is an important parameter to evaluate an anechoic chamber. The ray-tracing method has been applied to analyze it. However, the lowest applicable frequency has not been cleared. In this paper, the FDTD method has been applied to analyze the site attenuation of a compact anechoic chamber from 30 MHz to 250 MHz, and this has been compared with the calculated one by the ray-tracing method to evaluate the lowest frequency where the ray-tracing method could be applied. The compact anechoic chamber, where the absorbers are placed on the all walls, has been used for the calculation. For FDTD analysis, the dipole antenna and the absorber have been modeled by using the large cell, whose size is larger than the diameter of the antenna element. For verification, the site attenuation of a compact anechoic chamber has been measured and compared with the calculated values by the FDTD method and the ray-tracing method. As the results, the calculated values by the ray-tracing method have larger deviation than the ones by the FDTD method when the frequency is less than 180 MHz.

An ultra-small (0.3-mm0.3-mm0.06-mm) radio frequency identification chip called the µ-chip has been developed for use in a wide range of individual recognition applications. The chip is designed to be thin enough to be applied to paper and paper-like media that are widely used in retailing to create certificates with monetary value, as well as to token-type devices. The µ-chip has been designed and fabricated using 0.18-µm standard CMOS technology. This ultra-small RFID chip also has a low-cost oriented device structure of a double-surface electrode to simplify the process of connecting the antenna and chip. The measured characteristics of the prototype chip are presented, demonstrating the capability of the new chip as an RFID device.

A statistically uniform E-field is created in a reverberation chamber by moving mechanical stirrers to vary boundary conditions. The uniformity of the spatial electric-field distribution in an ideal reverberation chamber can be theoretically estimated by calculating the probability density function of its distribution. However, uniformity in an actual chamber is affected by the dimensions of the chamber and the structure of the stirrers. We experimentally and theoretically evaluated the effect of stirrers on the spatial uniformity of the average, median, and maximum electric-field distributions. When the dimensions of a chamber equipped with effective stirrers are large compared to the wavelength at the operating frequency, that is, when resonant modes above approximately 105 exist below the operating frequency, the spatial uniformity experimentally evaluated agrees well with theoretical values estimated by calculating the probability density function of their distributions.

This paper proposes resource management in Layer 1 Virtual Private Networks (VPNs). We have been proposing Layer 1 VPNs that provide layer 1 services to multiple customers over the single optical network with per VPN control and management capabilities. We have proposed two resource management models for Layer 1 VPNs, which constitute different class of services. One is the shared model, where resources are shared among VPNs. The other is the dedicated model, where resources are explicitly pre-assigned to each VPN. In this paper, after introducing an overview of Layer 1 VPNs, we evaluate several path computation algorithms for these two models focusing on the multi layer network scenario. In the shared model, there are several existing studies for non-VPN cases, but considerations for VPN cases are not investigated. This paper evaluates algorithms originally proposed for non-VPN cases for use in VPN cases. Simulation results show that the path computation algorithm that works as saving layer 1 resources achieves better resource sharing effect. In the dedicated model, the problem is identical to non-VPN cases. There is one conventional algorithm, but amount of available resources is not well considered. We propose a novel path computation algorithm. Simulation results show effectiveness of our proposed algorithm against the conventional algorithm. Furthermore, resource usage efficiency of two resource management models is compared. We analyze and propose applicability of resource management models.

In spatial multiplexing systems using multiple antennas, the error-rate performance is heavily dependent on the residual channel estimation error. In this letter, we propose a design method that uses the genetic algorithms to optimize training sequences for accurate channel estimation.

This paper presents a systematic methodology for the system-level assessment of signal integrity and electromagnetic compatibility effects in high-speed communication and information systems. The proposed modeling strategy is illustrated via a case study consisting of a critical coupled net of a complex system. Three main methodologies are employed for the construction of accurate and efficient macromodels for each of the sub-structures typically found along the signal propagation paths, i.e. drivers/receivers, transmission-line interconnects, and interconnects with a complex 3D geometry such as vias and connectors. The resulting macromodels are cast in a common form, enabling the use of either SPICE-like circuit solvers or VHDL-AMS equation-based solvers for system-level EMC predictions.

It has been demonstrated that a common-mode (CM) current can dominate the EMI processes up to 1 GHz, despite the fact that a CM current is smaller than a differential-mode (DM) current. However, this description is insufficient to describe behavior above 1 GHz. In this paper, the correspondence of CM and DM components for total electromagnetic (EM) radiation from a printed circuit board (PCB) with surface microstrip line, which is commonly used in microwave integrated circuits, at gigahertz frequency is studied experimentally and with finite-difference time-domain (FDTD) modeling. In order to characterize the EM radiation, the frequency response of the CM current, the electric field near the PCB, and the electric far field are investigated. First, the frequency response of the CM current, near and far-fields for the PCB with an attached feed cable are compared up to 5 GHz. Although the CM current decreases above a few gigahertz, near and far electric fields increase as the frequency becomes higher. Second, in order to distinguish between CM and DM radiation at high frequency, the frequency response and the angle pattern of the far-field from a PCB without the feed cable are discussed. The results show that radiation up to 1 GHz is related to the CM component. However, depending on polarization and PCB geometry, radiation may be dominated by the DM rather than the CM component. The results indicate that the DM component may be more significant relative to the CM component, and the increase in EM radiation can not be predicted from only the frequency response of CM current. Therefore, identifying the dominant component is essential for suppressing the EM radiation. This study is a basic consideration to realize a technique which is effective on the suppression of the EM radiation from the PCB with an attached feed cable.

A new generation method of rotating electromagnetic fields (rotating-EM fields) for radio frequency (RF) radiated immunity/susceptibility test and its basic characteristics are described. Two different double-side-band suppressed-carrier (DSB-SC) signals are required for generating the slowly rotating-EM field for the immunity/susceptibility test. These DSB-SC signals are generated by a DSB-SC-signal generator based on the new concept which consists of voltage-variable attenuators, bi-phase switches, a direct-digital synthesizer and a micro processor. Using the DSB-SC-signal generator, the DSB-SC signal of arbitrary RF frequency can be generated more easily than the conventional system. In this paper, the principle of the DSB-SC signal generator and the basic characteristics of the DSB-SC signals generated by the generator are clarified. The measured basic characteristics of the rotating-EM field generated using the new concept are shown and it is confirmed that the field can be applied for the RF immunity/susceptibility test. In addition, the susceptibility test of an equipment under test is made as an example, the validity of our proposed system is established.

Theoretical analyses are carried out on the height dependence of the antenna factor of an EMI antenna to develop an antenna calibration method that can provide the free-space value of the antenna factor. It is found that the antenna factor in general varies with the antenna height in a quasi-periodic way with a period of about λ/2. Thus, the present paper proposes to take an average of the antenna factors over a height range of about λ/2 to obtain an accurate estimate of the free-space antenna factor. Effective antenna arrangements are also proposed for the antenna calibration. Deviations in the estimate from the free-space antenna factor are less than 0.1 dB for tuned dipoles in the frequency range above 50 MHz. But the errors increase up to 0.3 dB at about 35 MHz. For broadband antennas, the free-space antenna factor can be accurately estimated by taking the average of the antenna factors. Errors are estimated to be less than 0.3 dB in the frequency range from 30 MHz to 1000 MHz.

A visualization method of coherent source locations based on the Sampled Pattern Matching (SPM) method is described. Modified SPM method is proposed to improve the S/N, in which the measurement of the electric field distribution is repeated in appropriate time duration and eigenvalue decomposition of the covariance matrix is introduced. A combination of the modified SPM method with the Weighted Subspace Fitting (WSF) method is also proposed to estimate accurate source locations. A calibration technique by using a reference antenna to compensate the complex pattern of the receiving antenna is proposed. Experimental investigation to estimate source location for one dipole antenna and two dipole antennas is also made to demonstrate the validity of the proposed method.

Future broadband mobile communication systems are necessary to achieve the bit rates of 100 Mbit/s. Orthogonal Frequency Division Multiplexing (OFDM) transmission is an attractive technology because it can remove the influence of frequency selective fading in broadband transmission by adding a suitable guard interval to each OFDM symbol. However, peak-to-average power ratio (PAPR) is very large in OFDM transmission. In this paper, we propose a new PAPR reduction method which can be applied even when unusable bands are inside the system band. In the proposed method, peak reduction signals are generated by iterative signal processing only in the usable frequency band, and filtering to remove out-of-band components of the peak reduction signals is incorporated into the iterative signal processing. The results of computer simulation show that the proposed method can effectively reduce peak power without expanding the spectrum both outside the system band and into unusable bands inside the system band. By using the proposed method, the broadband mobile communication system with low peak power and high flexibility of frequency band use can be realized.

In mobile communication systems, mobility tracking operations are executed to maintain known the whereabouts of each mobile terminal (MT). In this article, we propose and analyse two new versions of the original time-based registration method, namely the Stop and Wait (S W) and the Reset and Wait (R W) time-based strategies. We also propose and study the modified S&W and R&W schemes as a result of combining the S&W and R&W policies with the enhanced time-based method in [3]. When the MT uses one of the four schemes proposed, it sends less location update (LU) messages. As a result of fewer LUs, which results in less contacts with the network, the uncertainty of the MT position increases in the proposed time-based schemes. Although the MT paging (PG) cost is lightly increased, a significant reduction in the LU cost is achieved. As it is shown, the net effect is a saving in the total location management cost per call arrival. In order to analyse the four strategies and compare them with the original and enhanced time-based schemes, a performance evaluation method based on Markovian standard tools is proposed here. The location management cost for all these time-based policies are evaluated analytically here by using this evaluation method.

The latest video coding standard, H.264/AVC, adopts 44 approximate transform instead of 88 discrete cosine transform (DCT) to avoid the inverse transform mismatch problem. However, that is only one of the factors that make it difficult to transcode pre-coded video contents with the previous standards to H.264/AVC in the common domain without causing cascaded pixel-domain transcoding. In this paper, to support the existent DCT-domain transcoding schemes and to reduce computational complexity, we propose an efficient algorithm that converts the quantized 88 DCT block into four newly quantized 44 transformed blocks. The experimental results show that the proposed scheme reduces computational complexity by 5-11% and improves video quality by 0.1-0.5 dB compared with the cascaded pixel-domain transcoding scheme that exploits inverse quantization (IQ), inverse DCT (IDCT), DCT, and re-quantization (re-Q).

To offer location based services, service providers need to have access to Location Information (LI) regarding the users which they wish to serve; this is a potential privacy threat. We propose the use of constraints, i.e. statements limiting the use and distribution of LI, that are securely bound to the LI, as a means to reduce this threat. Constraints may themselves reveal information to any potential LI user--that is, the constraints themselves may also be a privacy threat. To address this problem we introduce the notion of a LI Preference Authority (LIPA). A LIPA is a trusted party which can examine LI constraints and make decisions about LI distribution without revealing the constraints to the entity requesting the LI. This is achieved by encrypting both the LI and the constraints with a LIPA encryption key, ensuring that the LI is only revealed at the discretion of the LIPA.