An adaptive data hiding scheme capable of hiding considerable quantities of secret data while preserving acceptable visual quality for cover images is proposed. The major idea of this scheme is to hide secret data into the compressed codes of cover image during the encoding process of side-match vector quantization (SMVQ) such that the interceptors will not capture the secret information. Based on the experimental results, it is confirmed that the proposed scheme is better than earlier works. Moreover, the receiver can efficiently receive both the compressed cover image and the hidden secret data at the same time.

In this paper, we propose a method to solve the distributed optimal power flow problem and discuss the associated implementation. We have combined this method with a projected Jacobi (PJ) method and a modified parallel block scaled gradient (MPBSG) method possessing decomposition effects. With the decomposition, our method can be parallel processed and is computationally efficient. We have tested our method for distributed OPF problems on numerous power systems. As seen from the simulation results, our method achieved a dramatic speed-up ratio compared with the commercial IMSL subroutines.

Recently, the direct conversion scheme has been actively investigated for the purpose of cost miniaturization and low power consumption of wireless receivers. IQ imbalance is one of the problems for the direct conversion receiver. In the case of OFCDM modulations, this IQ imbalance causes intercarrier interference (ICI) in the demodulated signals. In this paper, the decision directed scheme for IQ imbalance compensation is proposed. In the proposed scheme, the combination of received symbols which satisfies orthogonality conditions is used for compensation of IQ imbalance. Therefore, in addition to the pilot symbols, the received symbols can be used in order to improve the accuracy of the compensation matrix and BER can be reduced.

To achieve both of a high peak performance and low average power characteristics, frequency-voltage cooperative control processor has been proposed. The processor schedules its operating frequency according to the required computation power. Its operating voltage or body bias voltage is adequately modulated simultaneously to effectively cut down either switching current or leakage current, and it results in reduction of total power dissipation of the processor. Since a frequency-voltage cooperative control processor has two or more operating frequencies, there are countless scheduling methods exist to realize a certain number of cycles by deadline time. This proposition is frequently appears in a hard real-time system. This paper proves two important theorems, which give the power-minimum frequency scheduling method for any types of frequency-voltage cooperative control processor, such as Vdd-control type, Vth-control type and Vdd-Vth-control type processors.

Coupling between resonators are analyzed theoretically on basis of the coupled mode theory. New and basic equations for the coupling coefficient are derived and compared with those of waveguides. They should be useful for understanding the physical background of coupling and designing a new coupling scheme.

A new channel estimator that does not require a separate frequency offset estimator is proposed. The new algorithm has low complexity and low latency compared to the well-known weighted multi-slot averaging algorithm. The simulation results demonstrate the improved resistance to high Doppler frequency and high frequency offset.

Target reconstruction algorithm from its monostatic radar cross section (RCS) has been proposed for polygonal cylinders with curved surfaces. This algorithm is based on our previous finding that the main contribution to the back scattering is due to edge diffracted fields excited at a facet of nearly specular reflection direction. Dimension of this constitutive facet of the target is estimated from the local maxima and its lobe width in the angular RCS variation. Half and quarter circular cylinders are used as canonical scattering objects, and their measured and numerically simulated monostatic RCS values have been studied extensively to find scattering pattern characteristic difference between flat and circularly curved surfaces. Thus estimated constitutive facets are connected in order, and this procedure will be continued until the distance between the first and the final edges would be minimized. Our algorithm has been tested for other targets, and it is found that it works well for predicting metal convex targets with flat and curved facets.

Pattern extraction is an indispensable step in bare printed circuit board (PCB) inspection and plays an important role in automatic inspection system design. A good approach for pattern definition and extraction will make the following PCB diagnosis easy and efficient. The window-based technique has great potential in PCB patterns extraction due to its simplicity. The conventional window-based pattern extraction methods, such as Small Seeds Window Extraction method (SSWE) and Large Seeds Window Extraction method (LSWE), have the problems of losing some useful copper traces and splitting slanted-lines into too many small similar windows. These methods introduce the difficulty and computation intensive in automatic inspection. In this paper, a novel method called Contour Based Window Extraction (CBWE) algorithm is proposed for improvement. In comparison with both SSWE and LSWE methods, the CBWE algorithm has several advantages in application. Firstly, all traces can be segmented and enclosed by a valid window. Secondly, the type of the entire horizontal or vertical line of copper trace is preserved. Thirdly, the number of the valid windows is less than that extracted by SSWE and LSWE. From the experimental results, the proposed CBWE algorithm is demonstrated to be very effective in basic pattern extraction from bare PCB image analysis.

Ubiquitous computing (ubicomp) is a computing para-digm which utilizes human-centric systems and applications. With the widespread use of information appliances, robots and sensors, the ubicomp paradigm is expected to become a reality in the near future. Because close interaction between a person and the computing environment is required for ubicomp, autonomous decentralized control will play an important role. In this paper, we discuss autonomous decentralized control in ubicomp from the viewpoint of typical ubicomp applications, smart environments and context-awareness.

In pure peer-to-peer (P2P) file sharing applications and protocols using a flooding-based query algorithm, a large number of control packets (query packets) are transmitted on the network to search for target files. This clearly leads to a degradation of communication quality on the network and terminals as the number of users of the application increases. To solve such problems, this paper proposes: (1) a unified framework to describe a wide variety of query algorithms for pure P2P and (2) a new query algorithm based on this framework. Our framework determines the number of destinations for query packets based on the hop value recorded in received query packets. Simulation results revealed that the proposed query algorithm can reduce the overhead in the flooding-based query algorithm and k-random walks without decreasing the success rate of retrieval regardless of the density of target files in the network.

In this paper, a multiple-pulse signaling format for M-ary equicorrelated modulation (ECM) is proposed to enable the noncoherent detection on a multiple-symbol basis. Several time-limited and band-limited basis waveform sets are designed to embody the multiple-pulse ECM signals and explored to determine the spectral performance characteristics. Based on the maximum-likelihood decision principle, a block receiver is developed for noncoherently demodulating multiple-pulse ECM signals on additive white Gaussian noise channels. Tight upper and approximate bounds are derived and verified by simulation to evaluate the bit and symbol error probability characteristics of the developed ECM block receiver. It is analytically shown that the noncoherent M-ary ECM block receiver with a small-sized blocklength offers comparable performance to the ideal coherent M-ary simplex receiver when the pairwise signal correlation is appropriately chosen. In particular, the proposed noncoherent nonbinary simplex modulation is found to strongly outperform the conventional noncoherent nonbinary orthogonal modulation in terms of both power and spectral efficiencies.

We propose a multiple dwell serial search (MDSS) code acquisition for optical code-division multiple-access (O-CDMA) systems and theoretically analyze its performance. The search/lock strategy (SLS) is used as verification scheme for the multiple dwell detector. The operation of SLS is modeled by finite Markov chain to analyze the performance of the proposed system. Effect of system parameters, such as number of users, threshold and mean photon count per chip, on the performance of the proposed system is investigated. The theoretical result shows that the performance of the proposed system is less sensitive to parameter settings than the conventional single dwell serial search (SDSS) code acquisition system is. In addition, the proposed MDSS code acquisition system offers shorter mean acquisition time than that of conventional SDSS system.

In OFDM systems, employing a cyclic prefix (CP) as the guard interval is a simple way to combat the inter-symbol interference (ISI) and the inter-carrier interference (ICI), however it reduces the transmission efficiency of the system, especially for some channels with a very long delay spread. In this paper, we consider the OFDM system with insufficient CP, much more efficient than conventional OFDM systems. First, we present the system mathematical model and give the ISI and ICI analysis. Then the signal-to-interference power ratio (SIR) performance is presented. To reduce the ISI and ICI due to the insufficient CP, we develop a minimum-mean-square-error decision feedback equalizer (MMSE_DFE). Based on the MMSE criterion, the optimum feedforward and feedback filter coefficients are derived. For time-varying channel, to avoid brute force matrix inversion in conventional schemes, we propose an adaptive LMS based solution to update the filtering coefficients by tracing the channel variation. Since the high complexity of MMSE_DFE, a reduced complexity scheme, ordered successive partial interference cancellation DFE (OSPIC_DFE), is developed. From the performance comparison between the MMSE_DFE and the OSPIC_DFE, we see that the latter is very near to the former. Finally the simulation shows these proposed methods are highly effective in combating ISI and ICI with low complexity.

We demonstrate the C-band wavelength conversion unit having functions of automatic wavelength recognition, power equalization, and elimination of original signal and pumping light for the first time, which is based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's). The constructed unit automatically detects signal wavelength, sweeps wavelength of a pumping light, and adjusts center wavelengths of band pass filters and gain values of erbium-doped fiber amplifiers (EDFA's), in order to convert the wavelength of the signal to the arbitrary wavelength we set, and eliminate the original signal and pumping light after conversion. Amplification of the signal, pumping, and wavelength-converted lights compensates the detuning dependence of conversion efficiency and its asymmetry in the quantum-well (QW) SOA, to keep the power of the wavelength-converted light constant within the whole C-band region. The switching time of wavelength conversion by the unit is about a second, which is dominated by mechanical movement of the tunable filters. Wavelength-converted 2.5 and 10 Gb/s NRZ signals show clear eye-openings when the detuning is positive (ωp > ωs), and a 2-ps pulse train is also successfully wavelength-converted. To overcome the problem of the asymmetric conversion efficiency in the QW-SOA, we adopted quantum-dot (QD) SOA's. Although the 1.5 µm QD-SOA still shows its asymmetry, which will be improved by optimization of quantum dot structure, wavelength conversion of a 160 Gb/s RZ signal is demonstrated by the QD-SOA's. More improvement of the performance of the wavelength conversion unit should be possible by making switching time faster and installing the optimized QD-SOA's.

This paper introduces τk notation to be used to assess test generation complexity of classes of sequential circuits. Using τk notation, we reconsider and restate the time complexity of test generation for existing classes of acyclic sequential circuits. We also introduce a new DFT method called feedback shift register (FSR) scan design technique, which is extended from the scan design technique. Therefore, for a given sequential circuit, the corresponding FSR scan designed circuit has always equal or lower area overhead and test application time than the corresponding scan designed circuit. Furthermore, we identify some new classes of sequential circuits that contain some cyclic sequential circuits, which are τ-equivalent and τ2-bounded. These classes are the l-length-bounded testable circuits, l-length-bounded validity-identifiable circuits, t-time-bounded testable circuits and t-time-bounded validity-identifiable circuits. In addition, we provide two examples of circuits belonging to these classes, namely counter-cycle finite state machine realizations and state-shiftable finite state machine realizations. Instead of using a DFT method, a given sequential circuit described at the finite state machine (FSM) level can be synthesized using another test methodology called synthesis for testability (SFT) into a circuit that belongs to one of the easily testable classes of cyclic sequential circuits.

In conventional OFDM systems, the effect of inter-block-interference (IBI) can be completely removed by inserting sufficient redundant symbols between successive transmission blocks. In this paper, based on the reformulated received block symbols of the discrete multirate filterbanks model, a new transceiver model for the cyclic prefix (CP) OFDM systems is proposed, associated with the oblique projector technique (view as the pre-processor for achieving IBI-free). Consequently, a novel ISI-free receiver with the zero-order FIR zero-forcing (ZF) filterbanks equalizer can be devised, under noise-free environment. For performance comparison the bit-error-rate (BER) is investigated for the cases of noisy and noise-free channels. In all cases, viz., the length of CP is shorter or longer than the order of the channel impulse response, we show that the same BER performance compared with the one suggested in [3] can be achieved, under the same assumptions and conditions. Since a simple cascade configuration of the IBI cancellation using the oblique projector followed by the ISI cancellation using the zero-order FIR ZF filterbanks equalizer can be realized for OFDM systems with sufficient or insufficient CP, the complexity of transceiver design can be reduced.

In this letter, a new channel-adaptive beamforming method is proposed for OFDMA systems with smart antennas. In the method, the size of a cluster for resource unit is determined adaptively according to a region-splitting criterion. It is shown by simulations that the proposed method shows good performance in both frequency-flat and frequency-selective channels.

This letter describes an efficient architecture for a Software Defined Radio (SDR) Wideband Code Division Multiple Access (WCDMA) receiver using for high performance wireless communication systems. The architecture is composed of a Radio Frequency (RF) front-end, an Analog-to-Digital Converter (ADC), and a Quadrature Amplitude Modulation (QAM) demodulator. A coherent demodulator, with a complete digital synchronization scheme, achieves the bit-error rate (BER) of 10-6 with the implementation loss of 0.5 dB for a raw Quadrature Phase Shift King (QPSK) signal.

With VLSI design development, the increasingly severe power problem requests to minimize clock routing wirelength so that both power consumption and power supply noise can be alleviated. In contrast to most of traditional works that handle this problem only in clock routing, we propose to navigate standard cell register placement to locations that enable further less clock routing wirelength and power. To minimize adverse impacts to conventional cell placement goals such as signal net wirelength and critical path delay, the register placement is carried out in the context of a quadratic placement. The proposed technique is particularly effective for the recently popular prescribed skew clock routing. Experiments on benchmark circuits show encouraging results.

In this paper, an eight-legged resonant element is proposed for a multiband and dual-polarized frequency selective surface (FSS). The FSS element has two resonant frequencies for constructing two reflection bands, of which the separation can be easily controlled by adjusting the shape of the element. The flexibility is demonstrated by the simulated results of transmission responses for various geometrical parameters. And it is shown that introducing resonant-grid and closely-packing techniques can improve the reflection bandwidth. Finally, the good agreement between the measured and the calculated results proves that the eight-legged element is useful for the design of a multiband FSS.