Scalar multiplication methods using the Frobenius maps are known for efficient methods to speed up (hyper)elliptic curve cryptosystems. However, those methods are not efficient for the cryptosystems constructed on fields of small extension degrees due to costs of the field operations. Iijima et al. showed that one can use certain automorphisms on the quadratic twists of elliptic curves for fast scalar multiplications without the drawback of the Frobenius maps. This paper shows an extension of the automorphisms on the Jacobians of hyperelliptic curves of arbitrary genus.

An all-optical phase multiplexing scheme for phase-modulated signals is proposed and experimentally demonstrated using four-wave mixing (FWM) in a highly-nonlinear fiber (HNLF). Two 10-Gb/s π/2-shifted differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals are experimentally demonstrated to be converted and phase-multiplexed into a 20-Gb/s differential quadrature phase-shift keying (DQPSK) signal with non-return-to-zero (NRZ) and return-to-zero (RZ) formats, respectively. Experimental results show that, due to phase-modulation-depth doubling effect and phase multiplexing effect in the FWM process, a DQPSK signal is successfully generated through the proposed all-optical phase multiplexing with improved receiver sensitivity and spectral efficiency.

The least-squares linear filtering and fixed-point smoothing problems of uncertainly observed signals are considered when the signal and the observation additive noise are correlated at any sampling time. Recursive algorithms, based on an innovation approach, are proposed without requiring the knowledge of the state-space model generating the signal, but only the autocovariance and crosscovariance functions of the signal and the observation white noise, as well as the probability that the signal exists in the observations.

This paper proposes a novel MIMO system that introduces a heterogeneous stream (HTS) scheme and a blind signal detection method for mobile radio communications. The HTS scheme utilizes different modulation or coding methods for different MIMO streams, and the blind detection method requires no training sequences for signal separation, detection, and channel estimation. The HTS scheme can remove the ambiguity in identifying separated streams without unique words that are necessary in conventional MIMO blind detection. More specifically, two examples of HTS are considered: modulation type HTS (MHTS) and timing-offset type HTS (THTS). MHTS, which utilizes different modulation constellations with the same bandwidth for different streams, has been previously investigated. This paper proposes THTS which utilizes different transmission timing with the same modulation. THTS can make the blind detection more robust and effective with fractional sampling. The blind joint processing of detection and channel estimation performs adaptive blind MIMO-MLSE and is derived from an adaptive blind MLSE equalizer that employs the recursive channel estimation with the Moore-Penrose generalized inverse. Computer simulations show that the proposed system can achieve superior BER performance with Eb/N0 degradation of 1 dB in THTS and 2.5 dB in MHTS compared with the ideal maximum likelihood detection.

A key issue in QoS-provisioning real-time wireless communications is to provide the QoS requirement with low energy consumption. In this paper, we propose an energy-efficient error correction scheme for real-time communications with QoS requirements in wireless networks. The QoS requirement of a message stream is modeled with (m, k) constraint, implying that at least m messages should be sent to a receiver during any window of k periods. The proposed scheme adaptively selects an error correcting code in an energy-efficient manner so that it maximizes the number of QoS provisionings per unit energy consumption.

This paper presents a VLSI architecture of MMSE detection in a 44 MIMO-OFDM receiver. Packet-based MIMO-OFDM imposes a considerable throughput requirement on the matrix inversion because of strict timing in frame structure and subcarrier-by-subcarrier basis processing. Pipeline processing oriented algorithms are preferable to tackle this issue. We propose a pipelined MMSE detector using Strassen's algorithms of matrix inversion and multiplication. This circuit achieves real-time operation which does not depend on numbers of subcarriers. The designed circuit has been implemented to a 90-nm CMOS process and shows a potential for providing a 2.6-Gbps transmission speed in a 160-MHz signal bandwidth.

This paper presents a new method for reconstruction of trigonometric polynomials, a specific class of bandlimited signals, from a number of integrated values of input signals. It is applied in signal reconstruction, spectral estimation, system identification, as well as in other important signal processing problems. The proposed method of processing can be used for precise rms measurements of periodic signal (or power and energy) based on the presented signal reconstruction. Based on the value of the integral of the original input (analogue) signal, with a known frequency spectrum but unknown amplitudes and phases, a reconstruction of its basic parameters is done by the means of derived analytical and summarized expressions. Subsequent calculation of all relevant indicators related to the monitoring and processing of ac voltage and current signals is provided in this manner. Computer simulation demonstrating the precision of these algorithms. We investigate the errors related to the signal reconstruction, and provide an error bound around the reconstructed time domain waveform.

The paper reviews recent advances in on-body antennas and propagation under a joint UK EPSRC research project between Queen Mary College, University of London and University of Birmingham. The study of on-body radio propagation has been extended by using various small antennas. The effect of antenna size, gain and radiation patterns on on-body channel characteristics has been studied. A practical wearable sensor antenna design is presented and it is demonstrated that a global simulation including sensor environment and human body is needed for accurate antenna characterisation. A 3D animation design software, POSER 6 has been used together with XFDTD to predict the on-body path loss variation due to changes in human postures and human motion. Finally, a preliminary study on the feasibility of a diversity scheme in an on-body environment has been carried out.

This paper proposes a new control scheme in which the base station (BS) controls terminal's transmit beamforming in time-division duplex (TDD)/multi-input multi-output (MIMO) systems. In the proposed scheme, the BS transmits pilot signals using appropriate downlink beams to instruct a terminal on target transmit beamforming. Using responses of the downlink pilot signals, the terminal can perform transmit beamforming close to the target one. Our theoretical investigation reveals that the BS can control multiple terminals' transmit beamforming simultaneously. Furthermore, an efficient signal processing at the terminal is investigated to obtain precise weight of transmit beamforming in noise environments. Numerical results show that the terminal can perform precise transmit beamforming close to the target one in noise environments. It is also shown that the amount of downlink control signalling in the proposed scheme is much less than that in codebook-based approach.

Directions and speeds of the motion of rain areas are estimated for each type of rain fronts, using time differences detected in the rain attenuation of the Ku-band satellite radio wave signals that have been measured at Osaka Electro-Communication University (OECU) in Neyagawa, Osaka, Research Institute of Sustainable Humanosphere (RISH) in Uji, Kyoto, and MU Observatory (MU) of Kyoto University in Shigaraki, Shiga, for the past five years since September 2002. These directions and speeds are shown to agree well with those directly obtained from the motion of rain fronts in the weather charts published by Japan Meteorological Agency. The rain area motion is found to have characteristic directions according to each rain type, such as cold and warm fronts or typhoon. A numerical estimate of the effects of site diversity techniques indicates that between two sites among the three locations (OECU, RISH, MU) separated by 20-50 km, the joint cumulative time percentages of rain attenuation become lower as the two sites are aligned along the directions of rain area motion. In such a case, compared with the ITU-R recommendations, the distance required between the two sites may be, on an average, reduced down to about 60-70% of the conventional predictions.

Body movement synchrony (i.e. rhythmic synchronization between the body movements of interacting partners) has been described by subjective impressions of skilled counselors and has been considered to reflect the depth of the client-counselor relationship. This study analyzed temporal changes in body movement synchrony through a video analysis of client-counselor dialogues in counseling sessions. Four 50-minute psychotherapeutic counseling sessions were analyzed, including two negatively evaluated sessions (low evaluation groups) and two positively evaluated sessions (high evaluation groups). In addition, two 50-minute ordinary advice sessions between two high school teachers and the clients in the high rating group were analyzed. All sessions represent role-playing. The intensity of the participants' body movement was measured using a video-based system. Temporal change of body movement synchrony was analyzed using moving correlations of the intensity between the two time series. The results revealed (1) A consistent temporal pattern among the four counseling cases, though the moving correlation coefficients were higher for the high evaluation group than the low evaluation group and (2) Different temporal patterns for the counseling and advice sessions even when the clients were the same. These results were discussed from the perspective of the quality of client-counselor relationship.

Auditory artifacts due to switching head-related transfer functions (HRTFs) are investigated, using a software-implemented dynamic virtual auditory display (DVAD) developed by the authors. The DVAD responds to a listener's head rotation using a head-tracking device and switching HRTFs to present a highly realistic 3D virtual auditory space to the listener. The DVAD operates on Windows XP and does not require high-performance computers. A total system latency (TSL), which is the delay between head motion and the corresponding change of the ear input signal, is a significant factor of DVADs. The measured TSL of our DVAD is about 50 ms, which is sufficient for practical applications and localization experiments. Another matter of concern is the auditory artifact in DVADs caused by switching HRTFs. Switching HRTFs gives rise to wave discontinuity of synthesized binaural signals, which can be perceived as click noises that degrade the quality of presented sound image. A subjective test and excitation patterns (EPNs) analysis using an auditory filter are performed with various source signals and HRTF spatial resolutions. The results of the subjective test reveal that click noise perception depends on the source signal and the HRTF spatial resolution. Furthermore, EPN analysis reveals that switching HRTFs significantly distorts the EPNs at the off signal frequencies. Such distortions, however, are masked perceptually by broad-bandwidth source signals, whereas they are not masked by narrow-bandwidth source signals, thereby making the click noise more detectable. A higher HRTF spatial resolution leads to smaller distortions. But, depending on the source signal, perceivable click noises still remain even with 0.5-degree spatial resolution, which is less than minimum audible angle (1 degree in front).

Random variations in Id-Vg characteristics of MOS transistors in an LSI chip are shown to be concisely characterized by using only 3 transistor parameters (Vth, β0, vSAT) in the MOS level 3 SPICE model. Statistical analyses of the transistor parameters show that not only the threshold voltage variation, ΔVth, but also the current factor variation, Δβ0, independently induces Id-variation, and that Δβ0 is negatively correlated with the saturation velocity variation, ΔvSAT. Using these results, we have proposed a simple method that effectively takes the correlation between parameters into consideration when creating statistical model parameters for designing a circuit. Furthermore, we have proposed a sensitivity analysis methodology for estimating the process window of SRAM cell operation taking transistor variability into account. By applying the concise statistical model parameters to the sensitivity analysis, we are able to obtain valid process windows without the large volume of data-processing and long turnaround time associated with the Monte Carlo simulation. The process window was limited not only by ΔVth, but also by Δβ0 which enhanced the failure region in the process window by 20%.

Encapsulating critical computation subgraphs as application-specific instruction set extensions is an effective technique to enhance the performance of embedded processors. However, the addition of custom functional units to the base processor is required to support the execution of these custom instructions. Although automated tools have been developed to reduce the long design time needed to produce a new extensible processor for each application, short time-to-market, significant non-recurring engineering and design costs are issues. To address these concerns, we introduce an adaptive extensible processor in which custom instructions are generated and added after chip-fabrication. To support this feature, custom functional units (CFUs) are replaced by a reconfigurable functional unit (RFU). The proposed RFU is based on a matrix of functional units which is multi-cycle with the capability of conditional execution. A quantitative approach is utilized to propose an efficient architecture for the RFU and fix its constraints. To generate more effective custom instructions, they are extended over basic blocks and hence, multiple exits custom instructions are proposed. Conditional execution has been added to the RFU to support the multi-exit feature of custom instructions. Experimental results show that multi-exit custom instructions enhance the performance by an average of 67% compared to custom instructions limited to one basic block. A maximum speedup of 4.7, compared to a general embedded processor, and an average speedup of 1.85 was achieved on MiBench benchmark suite.

This paper considers numerical methods for stability analyses of periodic solutions of ordinary differential equations. Stability of a periodic solution can be determined by the corresponding monodromy matrix and its eigenvalues. Some commonly used numerical methods can produce inaccurate results of them in some cases, for example, near bifurcation points or when one of the eigenvalues is very large or very small. This work proposes a numerical method using a periodic boundary condition for vector fields, which preserves a critical property of the monodromy matrix. Numerical examples demonstrate effectiveness and a drawback of this method.

The subject of this paper is maximum weight matchings of graphs. An edge set M of a given graph G is called a matching if and only if any pair of edges in M share no endvertices. A maximum weight matching is a matching whose total weight (total sum of edge-weights) is maximum among those of G. The maximum weight matching problem (MWM for short) is to find a maximum weight matching of a given graph. Polynomial algorithms for finding an optimum solution to MWM have already been proposed: for example, an O(|V|4) time algorithm proposed by J. Edmonds, and an O(|E||V|log |V|) time algorithm proposed by H.N. Gabow. Some applications require obtaining a matching of large total weight (not necessarily a maximum one) in realistic computing time. These existing algorithms, however, spend extremely long computing time as the size of a given graph becomes large, and several fast approximation algorithms for MWM have been proposed. In this paper, we propose six approximation algorithms GRS+, GRS_F+, GRS_R+, GRS_S+, LAM_a+ and LAM_as+. They are enhanced from known approximation ones by adding some postprocessings that consist of improved search of weight augmenting paths. Their performance is evaluated through results of computing experiment.

This paper investigates the design curves of the class DE amplifier with the nonlinear shunt capacitances for any output Q and any grading coefficient m of the diode junction in the MOSFET. The design curves are derived by the numerical calculation using Spice. The results of this paper have two important meanings. Firstly, it is clarified that the nonlinearities of the shunt capacitances affect the design curves of the class DE amplifier, especially, for low output Q. Moreover, the supply voltage is a quite important parameter to design the class DE amplifier with the nonlinear shunt capacitances. Secondly, it is also clarified that the numerical design tool using Spice, which is proposed by authors, can be applied to the derivation of the design curves. This shows the possibility of the algorithm to be a powerful tool for the analysis of the class E switching circuits. The waveforms from Spice simulations denote the validity of the design curves.

The paper presents a novel approach to estimate the performance of MPI collective communications. Our objective is to help researchers to make appropriate decisions on their message-passing applications. For each collective communication, we attempt to apply LogGP and P-LogP standard point-to-point models. The resulted models are compared with the empirical data in order to identify the most suitable for performance characterization of collective operations. For the communications on large clusters with large size messages, the network contention problem can significantly affect the performance. Hence, to reduce the relative gap between the prediction and the measured runtime, the contention issue is also modeled, by a queuing theory analysis method, and taken in account with the total performance estimation. The experiments performed on a cluster which consists of 64 processors interconnected by Gigabit Ethernet network show encouraging results. For any collective operation, given a number of processors and a range of message sizes, there is at least one model that predicts the performance precisely. We could achieve a gap between the predicted and the measured run-time around 15%. Thus, by handling the contention problem, we could reduce around 80% of the relative gap.

Space-time block codes (STBCs) from coordinate interleaved orthogonal designs (CIODs) have attracted a great deal of attention due to their full-diversity and linear maximum likelihood (ML) decodability. In this letter, we propose a simple detection technique, particularly for full-rate STBCs from CIODs to overcome the performance degradation caused by time-selective fading channels. Furthermore, we evaluate the effects of time-selective fading channels and imperfect channel estimation on STBCs from CIODs by using a newly-introduced index, the results of which demonstrate that full-rate STBCs from CIODs are more robust against time-selective fading channels than conventional full-rate STBCs.

A branch-and-bound algorithm (BB for short) is the most general technique to deal with various combinatorial optimization problems. Even if it is used, computation time is likely to increase exponentially. So we consider its parallelization to reduce it. It has been reported that the computation time of a parallel BB heavily depends upon node-variable selection strategies. And, in case of a parallel BB, it is also necessary to prevent increase in communication time. So, it is important to pay attention to how many and what kind of nodes are to be transferred (called sending-node selection strategy). In this paper, for the graph coloring problem, we propose some sending-node selection strategies for a parallel BB algorithm by adopting MPI for parallelization and experimentally evaluate how these strategies affect computation time of a parallel BB on a PC cluster network.