This paper first reviews the trends of VLSI design, focusing on the power dissipation and programmability. Then, we show the advantage of Quarternary Decision Diagrams (QDDs) in representing and evaluating logic functions. That is, we show how QDDs are used to implement QDD machines, which yield high-speed implementations. We compare QDD machines with binary decision diagram (BDD) machines, and show a speed improvement of 1.28-2.02 times when QDDs are chosen. We consider 1-and 2-address BDD machines, and 3- and 4-address QDD machines, and we show a method to minimize the number of instructions.

In this letter, we present a real-time orientation estimation and motion tracking scheme using interacting multiple model (IMM) based Kalman filtering method. Two nonlinear filters, quaternion-based extended Kalman filter (QBEKF) and gyroscope-based extended Kalman filter (GBEKF) are utilized in the proposed IMM-based orientation estimator for sensor motion state estimation. In the QBEKF, measurements from gyroscope, accelerometer and magnetometer are processed; while in the GBEKF, sole measurements from gyroscope are processed. The interacting multiple model algorithm is used for fusing the estimated states via adaptive model weighting. Simulation results validate the proposed design concept, and the scheme is capable of reducing overall estimation errors in sensor motion tracking.

This paper presents the new switching converter model used for analyzing the generation mechanism of ringing ground leakage (GL) current, generated during the transient, at switch on/off of any switching converter. By applying the Norton model, the proposed new model of switching converter can be formulated. The ringing GL current is evaluated at the switching on/off of the unbalanced (half-bridge converter) and the balanced converter (full-bridge converter) for bidirectional D.C. motor drive used as an example. It is concluded that the measured and simulated results of the generated GL current agree well with the numerical analysis results, analyzed by the proposed new model of switching converter, in terms of the minimum or maximum peak currents and the ringing frequency.

Although the probabilistic model checking tool called PRISM has been applied in many communication systems, such as wireless local area network, Bluetooth, and ZigBee, the technique is not used in a controller area network (CAN). In this paper, we use PRISM to model the mechanism of priority messages for CAN because the mechanism has allowed CAN to become the leader in serial communication for automobile and industry control. Through modeling CAN, it is easy to analyze the characteristic of CAN for further improving the security and efficiency of automobiles. The Markov chain model helps us to model the behaviour of priority messages.

The paper presents a systematic study of in-situ passivated AlN/GaN Metal Insulator Semiconductor Field Effect Transistors (MISFETs) with submicron gates. DC, high frequency small signal, large signal and low frequency dispersion effects are reported. The DC characteristics are analyzed in conjunction with the power performance of the device at high frequencies. Studies of the low frequency characteristics are presented and the results are compared with those of AlGaN/GaN High Electron Mobility Transistors (HEMTs). Small signal measurements showed a current gain cutoff frequency and maximum oscillation frequency of 49.9 GHz and 102.3 GHz respectively. The overall characteristics of the device include a peak current density of 335 mA/mm, peak extrinsic transconductance of 130 mS/mm, a maximum output power density of 533 mW/mm with peak power added efficiency (P.A.E.) of 41.3% and linear gain of 17 dB. The maximum frequency dispersion of transconductance and output resistance of the fabricated MISFETs is 20% and 21% respectively.

Ad hoc networking uses wireless technologies to construct networks with no physical infrastructure and so are expected to provide instant networking in areas such as disaster recovery sites and inter-vehicle communication. Unlike conventional wired networks services, services in ad hoc networks are easily disrupted by the frequent changes in traffic and topology. Therefore, solutions to assure the Quality of Services (QoS) in ad hoc networks are different from the conventional ones used in wired networks. In this paper, we propose a new queue management scheme, Interference Drop Scheme (IDS) for ad hoc networks. In the conventional queue management approaches such as FIFO (First-in First-out) and RED (Random Early Detection), a queue is usually managed by a queue length limit. FIFO discards packets according to the queue limit, and RED discards packets in an early and random fashion. IDS, on the other hand, manages the queue according to wireless interference time, which increases as the number of contentions in the MAC layer increases. When there are many MAC contentions, IDS discards TCP data packets. By observing the interference time and discarding TCP data packets, our simulation results show that IDS improves TCP performance and reduces QoS violations in UDP in ad hoc networks with chain, grid, and random topologies. Our simulation results also demonstrate that wireless interference time is a better metric than queue length limit for queue management in multi-hop ad hoc networks.

This paper demonstrates an efficient modelling method for artificial materials using digital filtering (DF) techniques. To demonstrate the efficiency of the DF technique it is applied to an electromagnetic bandgap (EBG) structure and a capacitively-loaded loop the so-called, CLL-based metamaterial. Firstly, this paper describes fine mesh simulations, in which a very small cell size (0.10.10.1 mm3) is used to model the details of an element of the structures to calculate the scattering parameters. Secondly, the scattering parameters are approximated with Padé forms and then factorised. Finally the factorised Padé forms are converted from the frequency domain to the time domain. As a result, the initial features in the fine meshes are effectively embedded into a numerical simulation with the DF boundary, in which the use of a coarse mesh is feasible (1,000 times larger in the EBG structure simulation and 680 times larger in the metamaterial simulation in terms of the volumes). By employing the coarse mesh and removal of the dielectric material calculations, the heavy computational burden required for the fine mesh simulations is mitigated and a fast, efficient and accurate modelling method for the artificial materials is achieved. In the case of the EBG structure the calculation time is reduced from 3 hours to less than 1 minute. In addition, this paper describes an antenna simulation as a specific application example of the DF techniques in electromagnetic compatibility field. In this simulation, an electric field radiated from a dipole antenna is enhanced by the DF boundary which models an artificial magnetic conductor derived from the CLL-based metamaterial. As is shown in the antenna simulation, the DF techniques model efficiently and accurately large-scale configurations.

In this paper, we propose a new differential MIMO single-carrier system with frequency-domain equalization (SC-FDE) aided by the insertion of cyclic prefix. This block transmission system not only inherits all the merits of the SISO SC-FDE system, but is also equipped with a differential space-time block coding (DSTBC) such as to combat the fast-changing frequency selective fading channels without the needs to estimate and then compensate the channel effects. Hence, for practical applications, it has the additional merits of decoding simplicity and robustness against high mobility transmission environments. Computer simulations show that the proposed system can provide diversity benefit as the non-differential system does, while greatly reducing the receiver complexity.

ICI (Inter-Cell Interference) mitigation schemes at the cell border are frequently dealt with as a special issue in 3GPP LTE (Long Term Evolution). However, few papers have analyzed the outage performance for the ICI mitigation schemes. In this paper, we propose a generalized cell planning scheme termed QBPA (Quality of Service based Band Power Allocation). Utilizing the QBPA scheme, we measure how much increase in channel capacity can be obtained through the flexible control of bandwidth and power in multi-cell forward-link environments. In addition, the feasible performance of the conventional schemes can be evaluated as long as those schemes are specific forms of the QBPA.

In this paper, a novel CMA (constant modulus algorithm) algorithm employing fast convolution in the DFT (discrete Fourier transform) domain is proposed. We propose a non-linear adaptation algorithm that minimizes CMA cost function in the DFT domain. The proposed algorithm is completely new one as compared to the recently introduced similar DFT domain CMA algorithm in that, the original CMA cost function has not been changed to develop DFT domain algorithm, resulting improved convergence properties. Using the proposed approach, we can reduce the number of multiplications to O(Nlog2 N), whereas the conventional CMA has the computation order of O(N2). Simulation results show that the proposed algorithm provides a comparable performance to the conventional CMA.

A circular cavity resonance method is improved to measure the frequency dependence of complex permittivity of a dielectric plate by using multimode TE0m1 with integer m. The measurement principle is based on a rigorous analysis by the Ritz-Galerkin method. A new circular cavity with lowered height is designed from a mode chart of a cavity to decrease the number of unwanted modes near the TE0m1 modes. A copper cavity having 20 GHz for the TE011 mode was constructed based on this design. For glass cloth PTFE, RT/duroid 6010 and FR-4 dielectric plates, the frequency dependences are measured from resonant frequencies for the TE0m1 (m = 1, 2, 3 ...) modes. These measured results agree well with ones measured by using the conventional four different size cavities with TE011 mode. It is verified that the designed cavity structure is useful to measure the frequency dependence of low loss dielectric plates.

We investigate delay analysis of multi-hop wireless mesh network (WMN) where nodes have multi-channel and multiple transceivers to increase the network capacity. The functionality of the multi-channel and multiple transceivers allows the whole WMN to be decomposed into disjoint zones in such a way that i) nodes in a zone are within one-hop distance, and relay node and end nodes with different CWmins contend to access the channel based on IEEE 802.11e EDCA, ii) different channels are assigned to neighbor zones to prevent the hidden node problem, iii) relay nodes can transmit and receive the packets simultaneously by multi-channel and multiple transceivers. With this decomposition of the network, we focus on the delay at a single zone and then the end-to-end delay can be obtained as the sum of zone-delays. In order to have the location-independent end-to-end delay to the gateway regardless of source nodes' locations, we propose two packet management schemes, called the differentiated CW policy and the strict priority policy, at each relay node where relay packets with longer hop count are buffered in higher priority queues according to their experienced hop count. For the differentiated CW policy, a relay node adopts the functionality of IEEE 802.11e EDCA where a higher priority queue has a shorter minimum contention window. We model a typical zone as a one-hop IEEE 802.11e EDCA network under non-saturation condition where priority queues have different packet arrival rates and different minimum contention window sizes. First, we find the PGF (probability generating function) of the HoL-delay of packets at priority queues in a zone. Second, by modeling each queue as M/G/1 queue with the HoL-delay as a service time, we obtain the packet delay (the sum of the queueing delay and the HoL-delay) of each priority queue in a zone. Third, the average end-to-end delay of packet generated at end node in each zone is obtained by summing up the packet delays at each zone. For the strict priority policy, we regard a relay node as a single queueing system with multiple priority queues where relay packets in priority queues are served in the order of strict priority. Relay node has smaller CWmin than end node has and relay node competes with end nodes in a zone. Using the PGF of HoL-delay of packet at relay node and end node, we obtain the packet delay in a zone. The average end-to-end delay to the gateway generated at end node in each zone is obtained. Finally, for both the differentiated CW policy and strict priority policy, by equating all end-to-end delays to be approximately equal, we find the minimum contention window sizes of each priority queue numerically by trial and error method so that end-to-end delays of packets are almost equal regardless of their source's location, respectively. Numerical results show that proposed two methods obtain almost same end-to-end delay of packets regardless of their generated locations and our analytical results are shown to be well matched with the simulation results.

In this paper, the transmission and reflection properties of the microstrip line with bends are investigated using the Fourier transform and a mode-matching technique. Based on the waveguide model, the microstrip bends are modeled as the rectangular waveguides with perfect electric conducting top and bottom walls and perfect magnetic conducting side walls. Analytical closed-form expressions for transmission and reflection coefficients are developed using the residue calculus. To verify the proposed method, numerical computations are performed for comparison with 3D full-wave simulations and measurements. A quarter-wavelength transmission line scheme is also proposed to improve the signal integrity of double bend discontinuity.

In this letter, delay-dependent stability criterion for linear time-delay systems with multiple time varying delays is proposed by employing the Lyapunov-Krasovskii functional approach and integral inequality. By the N-segmentation of delay length, we obtain less conservative results on the delay bounds which guarantee the asymptotic stability of the linear time-delay systems with multiple time varying delays. Simulation results show that the proposed stability criteria are less conservative than several other existing criteria.

In this paper, we study the problem of processing continuous range queries in a hierarchical wireless sensor network. Recently, as the size of sensor networks increases due to the growth of ubiquitous computing environments and wireless networks, building wireless sensor networks in a hierarchical configuration is put forth as a practical approach. Contrasted with the traditional approach of building networks in a "flat" structure using sensor devices of the same capability, the hierarchical approach deploys devices of higher-capability in a higher tier, i.e., a tier closer to the server. While query processing in flat sensor networks has been widely studied, the study on query processing in hierarchical sensor networks has been inadequate. In wireless sensor networks, the main costs that should be considered are the energy for sending data and the storage for storing queries. There is a trade-off between these two costs. Based on this, we first propose a progressive processing method that effectively processes a large number of continuous range queries in hierarchical sensor networks. The proposed method uses the query merging technique proposed by Xiang et al. as the basis. In addition, the method considers the trade-off between the two costs. More specifically, it works toward reducing the storage cost at lower-tier nodes by merging more queries and toward reducing the energy cost at higher-tier nodes by merging fewer queries (thereby reducing "false alarms"). We then present how to build a hierarchical sensor network that is optimal with respect to the weighted sum of the two costs. This allows for a cost-based systematic control of the trade-off based on the relative importance between the storage and energy in a given network environment and application. Experimental results show that the proposed method achieves a near-optimal control between the storage and energy and reduces the cost by 1.002 -- 3.210 times compared with the cost achieved using the flat (i.e., non-hierarchical) setup as in the work by Xiang et al.

Integer codes are very flexible and can be applied in different modulation schemes. A soft decoding algorithm for integer codes will be introduced. Comparison of symbol error probability (SEP) versus signal-to-noise ratio (SNR) between soft and hard decoding using integer coded modulation shows us that we can obtain at least 2 dB coding gain. Also, we shall compare our results with trellis coded modulation (TCM) because of their similar decoding schemes and complexity.

In this paper, multiconductor transmission line (MTL) modelling is used to characterize the frequency response and dispersion of the low-voltage outdoor powerline channel. The analysis focuses on a single transmitter-to-receiver link and all the possible connection schemes associated with that link. By resorting to modal analysis, approximate analytical upper bounds of the channel frequency-response are derived for simplified but representative network configurations involving power cables with star-quad cross-section. Numerical solution of the MTL equations is used to validate the theoretical work and to show the dispersion of the channel frequency-responses, which results to be of the order of 20 dB.

The aim of this study is to develop a new whole-body averaged specific absorption rate (SAR) estimation method based on the external-cylindrical field scanning technique. This technique is adopted with the goal of simplifying the dosimetry estimation of human phantoms that have different postures or sizes. An experimental scaled model system is constructed. In order to examine the validity of the proposed method for realistic human models, we discuss the pros and cons of measurements and numerical analyses based on the finite-difference time-domain (FDTD) method. We consider the anatomical European human phantoms and plane-wave in the 2 GHz mobile phone frequency band. The measured whole-body averaged SAR results obtained by the proposed method are compared with the results of the FDTD analyses.

This paper proposes and verifies a specific absorption rate (SAR) measurement procedure for multi-antenna transmitters that requires measurement of two-dimensional electric field distributions for the number of antennas and calculation in order to obtain the three-dimensional SAR distributions for arbitrary weighting coefficients of the antennas prior to determining the average SAR. The proposed procedure is verified based on Finite-Difference Time-Domain (FDTD) calculation and measurement using electro-optic (EO) probes. For two reference dipoles, the differences in the 10 g SAR obtained based on the proposed procedure compared numerically and experimentally to that based on the original calculated three-dimensional SAR distribution are at most 4.8% and 3.6%, respectively, at 1950 MHz. At 3500 MHz, this difference is at most 5.2% in the numerical verification.

A scheme that jointly estimates carrier frequency offset and channel is proposed for the orthogonal frequency division multiplexing (OFDM) system. In the proposed scheme, the carrier frequency offset (CFO) and the channel state information (CSI) are first estimated by an minimum mean square error (MMSE) estimator and an maximum likelihood (ML) estimator, respectively. By exchanging the estimation information between these two estimators, the final estimation of CFO and CSI is then obtained by an iterative method. In the iterative process, the effect of imperfect CSI is considered. It can improve the estimation precision for a shorter preamble and accelerate the iterative convergence rate. To reduce the complexity of the proposed scheme, a procedure is adopted to eliminate the inverse operation of covariance matrix that is recalculated at each iteration. In addition, a sufficient condition for the convergence of the proposed method is deduced. The numerical simulation results show that the BER performance of our scheme is better than that of joint MLE for a shorter preamble and is comparable to that of joint MLE for a longer preamble. Furthermore, the average iterative time of our method is reduced by half as compared to the MLE methods without considering the effect of imperfect CSI.