Metallic pair lines transmitting high-frequency information signals above several tens MHz are often used without being twisted, as flat floor cable installed in buildings, ribbon-type cables installed in computer equipment, and traces in printed circuit boards. However, the conversion characteristics of untwisted unbalanced metallic pair lines connecting unbalanced circuits have not been investigated over a wide range of frequencies in the MHz region. First, we developed a method to estimate effective power conversion factors using a cascade connection of F matrices, where the unbalance in impedance and admittance of each pair line is distributed uniformly along the line. As a result some useful information was obtained about the balance-unbalance conversion characteristics of the effective power which can be used to suppress EMI phenomena in wiring, especially over several decades of high frequencies. Next, we attempted to apply the conversion characteristics of untwisted unbalanced pair lines obtained at frequencies below several MHz to techniques for searching for the return circuits of conductors installed in buildings. It was clarified experimentaly that the depth of the equivalent ground plane can be estimated by comparing the measured conversion values of TV feeder lines installed at the place being tested with reference values measured in advance on a copper plate .

A nonlinear multiple complex sinusoidal estimator (NMSE) is proposed, as an extended and improved version with system noise of the single sinusoidal estimator previously presented by the author, for extracting multiple complex sinusoids in white noise. This estimator is derived by applying an extended complex Kalman filter (ECKF) to a noisy multiple complex sinusoidal model with state-representation, where the model becomes a nonlinear stochastic system. Proof of the stability is given by using a structure of the state-space signal model and Lyapunov techniques. Also, computer simulations demonstrate the effectiveness of the NMSE from various points of view.

In the phase locked loop (PLL) frequency synthesizer which is used in a higher frequency region, the prescaler method is employed in order to increase the operating frequency of the programmable divider. However, since the fixed divider whose division ratio is same as the prescaler is installed at the following stage of the reference divider, the reference frequency is decreased and the performance of the PLL frequency synthesizer is degraded. The prescaler PLL frequency synthesizer using multi-programmable divider is one of the counter measures answering the request. In this paper we propose the reduction of the number of programmable dividers by using the (N+1/2) programmable divider. The effectiveness of the proposed method is confirmed by experimental results.

An improvement of the fiber-optic transceiver having both transmitter and receiver functions of optical time-domain reflectometers is examined. The improvement is achieved by introducing an external optical amplifier without changing the previously reported configuration. The characteristics of the transmitted Q-switched pulse and the receiver gain is studied theoretically and experimentally to estimate the performance improvement. It is found that the introduction of the external optical amplifier is a simple and effective way to the performance improvement.

The subject of the paper is to give an overview and latest results on the Legal Firing Sequence Problem of Petri nets (LFS for short). LFS is very fundamental in the sense that it appears as a subproblem or a simpler form of various basic problems in Petri net theory, such as the well-known marking reachability problem, the minimum initial resource allocation problem, the liveness (of level 4) problem, the scheduling problem and so on. However, solving LFS generally is not easy: it is NP -hard even for Petri nets having very simple structures. This intractability of LFS may have been preventing us from producing efficient algorithms for those problems. So research on LFS from computational complexity point of view seems to be rewarding.

The interaction between the human eye and electromagnetic (EM) waves in the ISM (industrial, scientific, and medical) frequency bands is investigated with the use of the finite-difference time-domain (FDTD) method. In order to assess possible health hazards, the specific absorption rates (SARs) are calculated and compared with the recommended safety standards. In particular, we calculate temperature rises in the human eye to assess the possibility of microwave-induced cataract formation. The results show that the maximum values of averaged SARs are less than the standard levels. In addition, we observed what is called the 'hot spot' in the region of eye humor at 2.4 GHz but not at 900 MHz and 5.8 GHz. Furthermore, the maximum temperature rise due to the incident EM power density of 5.0 mW/cm2, which is the MPE (maximum permissible exposure) limit for controlled environments, has been found to be at most 0.26 at 5.8 GHz, which is small compared with the threshold temperature rise 3.0 for cataract formation.

It is not rare case that a floated metal plate exists nearby high speed circuit traces. Heatsink placed on a IC chip nearby circuit traces, metal enclosure or circuit traces in a compact designed product may be a good example. It may be also seen such structure for a shield box and circuit traces confined. It is generally known that such metal plate as placing nearby circuit trace may change circuit trace parameters and then resonance frequency associated with the circuit trace. In this study, we clarified resonance frequency variation with comprehensive observation of input impedance of microstrip line that is an essential model of circuit traces on a printed circuit board. Since such structure is created in various cases in product designs, we believe that the results shown in this study may be useful for EMC design as well as signal integrity. For computation, method of moment was used.

In this paper, we propose optimization approaches for the parameter determination of the PNNI complex node model. Two optimal objectives are discussed: Least Square Approximation and Maximum Deviation Minimization. For each objective, we propose two practical criteria for setting up bypasses: Maximum Difference Removal and Largest Deviation Removal. Generalized inverse of matrix and linear programming techniques are used to find the solutions. The numerical results show that the least square approximation with the largest deviation removal criteria has the best performance as the number of bypasses increases.

This paper proposes a new self-healing scheme that differentiates the bandwidth requirement for each network service on ATM networks. First, we show the necessity of our proposed scheme. In the future network, we must satisfy two demands, rapid restoration from failure and differentiated bandwidth requirements. The conventional restoration scheme, called the self-healing scheme, realizes rapid restoration, but does not support bandwidth differentiation; the new self-healing scheme proposed herein does. We also show that the proposed scheme reduces the spare resources required for backup. The scheme can be realized as a simple extension of the conventional self-healing scheme. Finally, simulations show that the proposed scheme requires fewer spare resources while offering comparable restoration time to the conventional approach against any demand pattern.

Macrobending characteristics of a newly developed hetero-core splicing sensor is investigated from the viewpoint of the practical use intended both for relatively large distortion monitoring and for liquid adhesion detection. The hetero-core sensor can be simply fabricated by fusion splicing of a hetero-core fiber portion as short as approximately 5 mm in length, which is inserted in a typical low-transmission-loss single mode fiber with a 9-µm core diameter for the wavelength of 1.3 µm as a fiber network line. Two types of the sensor are typically realized in terms of the core diameters of 3 and 5 µm for the inserted hetero-core portion which are referred to as 9-3-9 and 9-5-9 types, respectively , with showing their distinct bending loss characteristics. This paper deals with the explorative applications of the two types of hetero-core sensors in which a bending-to-linear displacement converter and a liquid adhesion sensor are successfully examined using a 9-5-9 structure with its low insertion loss and a cladding interactive 9-3-9 structure with its high sensitivity, respectively. The low-insertion loss 9-5-9 sensor has shown the capability of monitoring millimeters-order distortion in low transmission loss fiber networks. On the other hand, the 9-3-9 type has found to be a prospective sensor for liquid adhesion detection. Operational mechanisms for these two sensors are also discussed in terms both of optical leaks occurring at the hetero-core interfaces and of the build-up of cladding modes which might interrogate the outer cladding boundary conditions of the hetero-core sensor.

Closed-loop power control providing maximum capacity of the multicarrier channel with frequency selective Nakagami fading is investigated. Use of the famous Gallager channel capacity (water-filling) theorem with the assumption of limited transmitter power and independent fading in partial channels leads to the algorithm for their optimal power loading. Analytical expressions for the capacity of the multicarrier channel as a function of the number of its subchannels and the fading parameters are derived for the cases of Optimal Power Distribution (OPD) and Equal Power Distribution (EPD). The dependence of the capacity gain on the OPD system order, the fading depth and the average SNR due the optimal power control is obtained. Comparison of the power efficiencies of the systems with OPD and EPD is presented.

This letter proposes a combined input- and crosspoint-queued (CIC) switch in which virtual output queuing (VOQ) is used at each input port. This CIC switch has a large buffer at each input port and a small buffer at each crosspoint. It does not require high-speed memory access or high-speed internal cell transmission lines. Since the performance of the CIC switch depends on the scheduling algorithms, we propose new scheduling algorithms for the CIC switch. Numerical results show that the mean cell delay time performance of the CIC switch using the proposed scheduling algorithms is better than that of an input-queued ATM switch. In addition, the required buffer size for the CIC switch using the proposed scheduling algorithms is smaller than that for a crosspoint-queued ATM switch.

To provide QoS guarantees for each connection, efficient scheduling algorithms, such as WFQ, have been proposed. These algorithms assume a certain amount of buffer is allocated for each connection to provide loss free transmission of packets. This buffer allocation policy, however, requires much buffer space especially when many connections are sharing a link. In this paper we propose the use of partial buffer sharing (PBS) policy combined with usage parameter control (UPC) for efficient buffer management and flexible QoS control in ATM switches. We evaluate the feasibility of the proposed method by solving a Markov model. We also show that using the proposed method, we can control the cell loss ratio (CLR) independently of the delay. Numerical evaluations are presented, which indicates the PBS combined with UPC significantly reduces the buffer size required to satisfy given cell loss ratios.

A multi-QoS scalable-distributed-arbitration (MSDA) ATM switch is described that supports both high- and low-priority traffic under the head-of-line-priority discipline. It uses crosspoint and transit buffers, each consisting of a high- and low-priority buffer. The buffers arbitrate in a distributed manner the selection of which cellsto transmit. The MSDA switch supports multiple QoS classes while still providing the scalability of a previously described single-QoS scalable-distributed-arbitration (SSDA) switch. A problem occurs when the delay-time-based cell-selection mechanism used in the SSDA switch is applied to the low-priority traffic: it cannot achieve fairness in terms of throughput. This problem is overcome by introducing a distributed-ring-arbiter-based cell-selection mechanism at each crosspoint for the low-priority traffic. The low-priority transit buffer at each crosspoint has virtual queues, one for each upper input port. Cells for the low-priority traffic are selected by distributed-ring arbitration among the low-priority crosspoint buffer and these virtual queues. For the high-priority traffic, the same delay-time-based cell-selection mechanism is used as in the SSDA switch. Simulations show that the MSDA switch ensures fairness interms of delay time for the high-priority traffic and ensures fairness in terms of throughput for the low-priority traffic.

This paper describes a 270-MHz CMOS quadrature modulator (QMOD) for a global system for mobile communications (GSM) transmitter. QMOD consists of two attenuators and two doubly-balanced modulators (DBM's) and fabricated by using 0.35-µm CMOS process. The carrier leakage level of -35.7 dBc and the image rejection level of -45.1 dBc are achieved. It's total chip area is 880 µm550 µm and it consumes 1.0 mA with 3.0 V power supply.

This paper proposes the iterative quasi-oldest-cell-first (i-QOCF) scheduling algorithm, a new scheduling algorithm for input-queued ATM switches with virtual output queuing (VOQ). In the i-QOCF scheduling algorithm, each input port and each output port maintains its own list. The length of the list can be N, 2 N, ..., B N, where B is the size of the separate queue for an output port at input ports, and N is the number of output ports. The list maintained by an input port contains the identifiers for those output ports to which that input port will send a cell. The list maintained by an output port contains the identifiers for input ports that have a cell destined for that output port. If we use a list whose length is B N, then the identifiers in the list appear in the oldest order, and i-QOCF gives preference to cells that have been waiting for the longest time. If we use a list whose length is less than B N, then the identifiers in the list appear in the quasi-oldest order, and i-QOCF gives preference to cells that have been waiting for the quasi-longest time. We determine the performance of i-QOCF in a comparison with i-OCF in terms of cell delay time. We find that an input-queued ATM switch with i-QOCF and VOQ can achieve 100% throughput for independent arrival processes. Under uniform traffic, 3-QOCF is enough to achieve convergence during one cell time. If we use 3-QOCF, the list length is 3 N, then its cell delay time is almost the same as that of 4-OCF (Oldest-Cell-First).

In uplink data communication in wireless networks, a portable computer may retransmit a packet multiple times before the base station receives the correct one. Each retransmission consumes communication bandwidth and battery energy of the portable computer. Therefore, it is desirable to reduce the number of retransmissions. In this paper, we propose the aggressive packet combining scheme for this purpose. The base station executes this scheme to combine multiple erroneous copies as follows: (1) perform bit-by-bit majority voting on the erroneous copies to produce a combined packet, (2) identify the least reliable bits in this combined packet, and (3) search the correct bit pattern for these bits. Then the base station may recover the correct packet, thereby reducing the mean number of retransmissions. The proposed scheme has several advantages: (1) it is more powerful than the majority packet combining scheme, (2) it can complement many existing ARQ protocols to improve their performance, (3) it does not add additional bits to the packet and hence it does not consume extra bandwidth in the wireless channel, and (4) it is only executed by the base station and hence the portable transceiver can be kept simple. The simulation results show that the proposed scheme is more bandwidth-efficient and energy-efficient than the majority packet combining scheme.

Medium access control (MAC) protocol is one of the key components for providing quality of service (QoS) in wireless ATM (W-ATM) networks. In this paper, we propose a hierarchical scheduling scheme coupled with fair queueing algorithms with adaptive weights. This scheme is intended to be applicable to a TDMA/TDD based MAC protocol. Specifically, the performance of the fair-queueing algorithm using fixed weights and adaptive weights is evaluated and compared. Simulation results show that the proposed hierarchical fair-queueing scheduling with adaptive weights (HAW) can yield a lower cell transfer delay and a higher channel utilization while maintaining fairness among multiple users.

The wall admittance of an arbitrarily shaped microstrip antenna is generally formulated. As examples, elliptical microstrip antennas with and without a circular slot are calculated. The wall admittance is determined by the spectral domain analysis in order to consider the effect of the dielectric substrate. The electromagnetic fields within the cavity are expanded in terms of the eigenfunctions in the cylindrical coordinate system and their expansion coefficients are determined by applying the impedance boundary condition at the aperture in the sense of the least squares. The calculated input impedance and axial ratio agree fairly well with the experimental data. The proposed method is valid for the microstrip antennas with a patch whose geometry deviates from the particular coordinate system, such as single-feed circularly polarized microstrip antennas.

In this paper, an algorithm of the median-cut quantization (MCQ) is proposed. MCQ is the technique that reduces multi-valued samples to binary-valued ones by adaptively taking the median value as the threshold. In this work, the search process of the median value is derived from the quick-sort algorithm. The proposed algorithm searches the median value bit by bit, and samples are quantized during the search process. Firstly, the bit-serial procedure is shown, and then it is modified to the bit-parallel procedure. The extension to the multi-level quantization is also discussed. Since the proposed algorithm is based on bit operations, it is suitable for hardware implementation. Thus, its hardware architecture is also proposed. To verify the significance, for the application to the motion estimation, the performance is estimated from the synthesis result of the VHDL model.