A novel formulation for the Scalar-field approach of Integral Equation formulation of the Measured Equation of Invariance (SIE-MEI) is derived from the scalar reciprocity relation to solve the scalar Helmholtz equation. The basics of this formulation are similar to IE-MEI method for the electromagnetic (EM) problem. The surface integral equation is derived from reciprocity relation and on-surface MEI postulates are used. As a result it generates a sparse linear system with the same number of unknowns as of Boundary Element Method (BEM) and keeps the merits in minimum storage memory requirements and CPU time consumption for computing the final matrix. IE-MEI method has been proposed for two-dimensional (2D) electromagnetic problem, but three-dimensional (3D) problem is very difficult to be extend. This scalar-field approach of IE-MEI method is identical to electromagnetic in 2D, but easily extended to the 3D scalar-field scattering problem contrary to EM problem. The numerical results of sphere and cube are verified with some rigorous or numerical solutions, which give excellent agreement.

This paper proposes a multi-hop wireless link system for radio access networks (RANs) of new generation mobile communication systems. The performance of the multi-hop wireless link system is evaluated from the viewpoints of total output power, co-frequency interference characteristics, and the system frequency bandwidth based on a comparison with that of the single-hop wireless link system, which is currently used as a RAN. The proposed system is effective in realizing an enormous approach link capacity from both the total output power and the co-frequency interference viewpoints. From the system frequency bandwidth viewpoint, the optimum number of relays in the multi-hop connection is determined to be three hops in a line-of-sight propagation environment in order to minimize the frequency bandwidth for transferring traffic. We conclude that the multi-hop wireless link system is suitable for new generation mobile communication systems.

This paper proposes a new method of retrieving images from large image databases. The method is based on VQ (Vector Quantization) of local texture features at interest points automatically detected in an image. The texture features are extracted by Gabor wavelet filter bank, and rearranged for rotation. These features are classified by VQ and then construct a pattern histogram. Retrievals are performed by just comparing pattern histograms between images.

A circuit that carries out an Hadamard transform of an input image using the pulse width modulation technique is proposed. The proposed circuit architecture realizes the function of an Hadamard transform with a full-size pixel image. A test chip that we designed and fabricated integrates 64 64 pixels in a 4.9 mm 4.9 mm area, with 0.35 µm CMOS technology. The functional operation and linearity of this chip are measured. An image processing application utilizing this chip is demonstrated.

This paper introduces an improved multistage parallel interference cancellation (PIC) technique that uses the reverse-link synchronous transmission technique (RLSTT) to improve the estimation of data at the initial stage. Because the subtraction of an interfering signal based on an incorrect bit decision quadruples the interference power for that signal, the relatively high decision bit error rate (BER) may lead to a poor cancellation or even a higher BER at the following stages. The RLSTT is a robust approach which takes into account the fact the tentative decision at the earlier stages is less reliable than the following stages and makes the earlier cancellation more reliable. The analysis demonstrates that a better transmission performance can be achieved by using the RLSTT at the initial stage of PIC.

The performances of M-ary PSK (MPSK) and QAM (MQAM) systems using L-branch selection combining (SC) diversity reception in frequency-nonselective slow Nakagami fading channels are derived theoretically. For integer values of the Nakagami fading parameter m, the general formula for evaluating symbol error rate (SER) of MPSK signals in the independent branch diversity system comprises numerical analyses with the integral-form expressions. An exact closed-form SER performance of MQAM signals under the effect of SC diversity via numerical integration is presented.

This paper presents the basic design and principles of an FQDN-based Internet Architecture, where a host is identified in the Internet only by its FQDN (Fully Qualified Domain Name). The address shortage problem for the IPv4 paradigm has been marginally solved by introducing private addresses within the intranet and also by DHCP for public Internet access services. These two approaches have been independently developed. Considering more elaborate peer-to-peer communications such as voice over IP (VoIP) in the future Internet, the shortage of address space will become a serious problem for a call or session to be established. To alleviate this, this paper proposes an FQDN-based Internet architecture, assuming that a global endpoint identifier (EID) in the network is FQDN instead of an IP address. Since a countably infinite number of addresses can be logically produced by FQDN, this system resolves the address shortage problem assuming a caller uses the FQDN of the called terminal or host. This requires a dynamic address loading system from the FQDN of the called terminal into one of the available public IP addresses. After proposing a possible address loading system, some mathematical results on the required number of public addresses for VoIP traffic, the address space size of the derived Internet, etc. are also presented.

In this letter we present a new way for computing generalized eigenvalue problems in engineering applications. To transform a generalized eigenvalue problem into an associated problem for solving nonlinear dynamic equations by using optimization techniques, we can determine all eigenvalues and their eigenvectors for general complex matrices. Numerical examples are given to verify the formula of dynamic equations.

In this paper, we present new stability conditions for a class of large-scale hybrid dynamical systems composed of a number of interconnected hybrid subsystems. The stability conditions are given in terms of discontinuous Lyapunov functions of the stable hybrid subsystems. Furthermore, the stability conditions are represented by LMIs (Linear Matrix Inequalities) which are computationally tractable.

This letter addresses a neural network (NN)-based predictor for the LP (Linear Prediction) residual. A new NN predictor takes into consideration not only prediction error but also quantization effects. To increase robustness against the quantization noise of the nonlinear prediction residual, a constrained back propagation learning algorithm, which satisfies a Kuhn-Tucker inequality condition is proposed. Preliminary results indicate that the prediction gain of the proposed NN predictor was not seriously decreased even when the constrained optimization algorithm was employed.

We developed a distributed control algorithm to solve the problem of a trade-off between transient response and stability. We applied it to a congestion control algorithm for transmitting best-effort packets such as transmission control protocol (TCP) packets over the Internet. A new transmission power control algorithm suitable for transmitting best-effort packets over the wireless Internet was also developed using the distributed control algorithm. We showed that in a steady state, TCP connections can use the bandwidth efficiently over both wired and wireless Internet when the proposed control algorithms are used. The transient response was also evaluated and it was found that the packet transmission rate and the transmission power adjusted by the proposed control algorithms converge to a steady state faster than when adjusted by conventional control algorithms while maintaining the stability of network systems.

This paper describes a single-chip RF transce-iver LSI for 2.4-GHz-band Bluetooth applications. This chip uses a 0.5 µm BiCMOS process, which provides 23 GHz fT. The LSI consists of almost all the required RF and IF building blocks--a power amplifier (PA), a low noise amplifier (LNA), an image rejection mixer (IRM), channel-selection filters, a limiter, a received signal strength indicator (RSSI), a frequency discriminator, a voltage controlled oscillator (VCO), and a phase-locked loop (PLL) synthesizer. The transceiver consumes 34.4 mA in TX mode (PA, VCO, PLL) and 44.0 mA in RX mode (LNA, IRM, channel-selection filters, limiter, RSSI, frequency discriminator, VCO, PLL). Direct-up conversion with a frequency doubler is used for the TX architecture. In order to avoid the VCO pulling, we used a 1.2 GHz VCO with the frequency doubler. In the receiver section, a low-IF single conversion RX architecture is employed for the integration of the channel-selection filters. The transceiver has a proposed linear frequency discriminator with a wide input range. The wide input-frequency range discriminator is required to realize the lower IF RX architecture because of the higher ratio of frequency deviation to the center IF frequency. The discriminator is the delay line type, and consists of a mixer and a delay line circuit with a locked loop. The delay line connects to one input terminal of the mixer. By using the delay locked at one fourth of the period of the IF frequency, a quadrature phase shift IF signal is applied to the mixer input terminal. For the frequency discriminator, the DC output voltage changes in proportion to the input frequency and a wide input range is achieved. This RF transceiver sufficiently satisfies all the target specifications for short-range Bluetooth applications. By using this chip, a -80 dBm sensitivity is obtained for the 10-3 BER, and the transceiver can deliver an output power of over 0.0 dBm.

In this paper, we study the following problem: given two graphs G, H and an isomorphism φ between an induced subgraph of G and an induced subgraph of H, compute the number of isomorphisms between G and H that do not contradict φ. We show that this problem can be solved in O(((k+1)(k+1)!)2n3) time when the input graphs are restricted to chordal graphs with clique number at most k+1. To prove this, we first show that the tree model of a chordal graph can be uniquely constructed in O(n3) time except for the ordering of children of each node. Then, we show that the number of φ-isomorphisms between G and H can be efficiently computed by use of the tree model.

We derived the design requirements that wireless systems and congestion control algorithms must satisfy to transmit best-effort Internet protocol (IP) packets over wireless systems. We proved that, if these requirements are satisfied, congestion control algorithms are robust against unfairness in the systems and can provide near-maximum throughputs in various environments. From the viewpoint of the design requirements, we investigated the effect of automatic repeat request (ARQ) on the throughputs of best-effort IP connections, and showed why ARQ can improve the throughputs while too large a number of retransmissions degrade them. We also investigated the effect of variance in packet transmission rates and clarified what kind of congestion control algorithm degrades the throughputs.

We propose using a soft decision-directed least-mean-square algorithm in a code-aided equalization scheme for fading channels. Soft-output Viterbi algorithm (SOVA) is modified and applied to strengthen the second-stage equalizer adaptation in the scheme. Simulation results are presented for bit error rate performance in a multipath environment for various normalized fade rates. The proposed equalizer scheme is shown to provide significant bit error rate improvement compared to conventional equalization schemes.

This paper investigates the cell search time performance of our previously proposed three-step cell search method in a two-cell site environment by laboratory and field experiments supporting asynchronous cell site operation, which is one of the most notable features of wideband direct sequence code division multiple access (W-CDMA) mobile communications. The cell search methods used in the paper are based on the ongoing third generation partnership project (3GPP), in which our original scheme was refined with respect to several points in order to reduce the complexity of the receiver. The experimental results demonstrate that the method achieves the fast cell search time of less than one second in real multipath-fading channels. The cell search is accomplished in less than approximately 700 msec at 90% of the detection probability when 4.7% and 0.5% of the total transmit power of a cell site is assigned to the common pilot channel (CPICH) and synchronization channels (SCHs), respectively, in a two-cell site environment. We also elucidate that the cell search time at the detection probability of 90% using time switched transmit diversity (TSTD) is decreased by approximately 100 msec compared to that without TSTD in low-mobility environments such as the average vehicular speed of 5 km/h with a transmit power assignment of the CPICH of 4.7%.

Methods that precisely compensate for propagation distortion using pilot symbols are widely used in mobile communications. We describe such a pilot-symbol-assisted technique for precise compensation of flat fading and frequency offset. This technique provides a wide range of offset compensation. Conventional methods using fast Fourier transform (FFT) compensate for both slow and fast fading, but their tolerable range of frequency offset is very limited. By composing a system with an approximate frequency estimator, we can estimate and compensate for fading and a large frequency offset at the same time. The estimation and compensation are carried out by periodic pilot symbols and no other index sequences are needed. This method enables high-data-rate transmission. We describe the method and provide a theoretical analysis for the compensable range of fading and frequency offset for a transmission frame structure with pilot symbols. Then, we evaluate the method by computer simulation.

This paper presents an efficient scheme for access bandwidth control for VBR (Variable Bit Rate) traffic between radio mobile terminals and their base stations in a WATM (Wireless ATM) network. After introducing the wireless ATM system model, we describe a new algorithm that enables dynamic slot allocation under TDMA/TDD (Time Division Multiple Access/Time Division Duplex) Media Access Control, making use of UPC (Usage Parameter Control) parameters and traffic characteristics. We show more efficient bandwidth utilization with our proposed algorithm, compared to other conventional algorithms. Moreover, we reveal that our algorithm improves cell transmission delays.

In this paper, we propose a new fair queueing algorithm to improve cell delay variation (CDV) for real-time service categories and to make efficient use of system resources for multimedia traffic in high speed ATM networks. The proposed algorithm is called the delay variation-based fair queueing (DVFQ) algorithm, which is based on per-VC queueing to improve CDV and fairness for each VC of real-time services such as CBR and rt-VBR. In DVFQ algorithm, we define two fairness indexes, which indicate the degree of the fairness of CDV at the rate of each VC, and the degree of impartially sharing the bandwidth between the scheduled cells for each VC. The simulation results for both heavily and lightly loaded conditions show that DVFQ algorithm provides better performances in terms of the CDV, the CDV fairness, and the service fairness than those of FCFS for real-time service.

To diffuse multimedia information services, communication networks must guarantee the quality of services (QoSs) requested by users. In addition, users should be allowed to observe the network in order to customize their own services. A new network management architecture is therefore essential. It must perceive not only node connectivity, but also network failure points and the traffic situation dynamically. This paper introduces the network map as such an architecture on personalized multimedia communication networks and proposes multiple QoS routing using the network map. Moreover, a prototype system is built in order to verify the availability of the network map.