Petri net is a powerful modeling tool for concurrent systems. Subclasses of Petri net are suggested to model certain realistic applications with less computational cost. Structurally weakly persistent net (SWPN) is one of such subclasses where liveness is verified in deterministic polynomial time. This paper studies the computational complexity to verify whether a give net is SWPN. 3UNSAT problem is reduced to the problem to verify whether a net is not SWPN. This implies co-NP completeness of verification problem of SWPN.

Accurate channel estimation for multiple cells is essential in downlink coordinated multi-point (CoMP) transmission/reception. Therefore, this paper investigates a technique to improve the channel estimation for downlink CoMP in Long-Term Evolution (LTE)-Advanced. In particular, the performance of data signal muting, i.e., muting data signals that collide with the channel state information reference signal (CSI-RS) of a neighboring cell, is evaluated considering various CoMP schemes and intra-eNodeB and inter-eNodeB CoMP scenarios. In a multi-cell link level simulation, coordinated scheduling and coordinated beamforming (CS/CB) CoMP is employed. The simulation results show that data signal muting is effective in improving the channel estimation accuracy, which is confirmed by numerical analysis. Simulation results also show that it is effective in improving the throughput performance, especially for sets of user equipment at the cell boundary. Furthermore, the tradeoff relationship between accurate channel estimation by muting larger numbers of data signals and a high peak data rate, i.e., low overhead, is investigated. It is shown that when the number of coordinated cells is set to three, the CSI-RS reuse factor is set to three, and the well-planned CSI-RS pattern allocation is employed, the improvement in performance is almost saturated in a synchronized network.

Cognitive radio is a promising approach to ensuring the coexistence of heterogeneous wireless networks since it can perceive wireless conditions and freely switch among different network modes. When there are many network opportunities, how to decide the appropriate network selection for CR user's current service is the main problem we study in this paper. We make full use of the intelligent characteristic of CR user and propose a fuzzy learning based network selection scheme, in which the network selection choice is made based on the estimated evaluations of available networks. Multiple factors are considered when estimating these evaluations. Both the outer environment factors directly sensed by CR user (signal strength of the available network and network mode), and also the factor that cannot be determined beforehand and is learnt by our scheme (the bandwidth allocated by the optional network) are considered. From several interactions with the wireless environment, the experience of network selection behavior is accumulated which will direct our scheme to make a proper decision of the network. Two simulations verify that our scheme could not only guarantee a better bandwidth requirement of CR user compared with other three network selection methods, but also shows it to be a reasonable scheme for utilizing the available resources of these networks.

A readout circuit incorporating a pixel-level analog-to-digital converter (ADC) is studied for 2-dimensional microbolometer infrared focal plane arrays (IRFPAs). The integration time and signal-to-noise ratio (SNR) is improved using the current-mode bias and MSB skimming. The proposed pixel-level ADC is a two-step configuration, so its power consumption is very low. The readout circuit was designed using a 0.35 µm 2-poly 4-metal CMOS process for a 320240 microbolometer array with a pixel size of 35µm35µm. The noise equivalent temperature difference (NETD) was estimated to be 47 mK, with a power consumption of 390 nW for a pixel-level ADC.

We fabricated solution-processed organic complementary inverters based on α,ω-bis(2-hexyldecyl)sexithiophene (BHD6T) for p-channel and C60-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12) for n-channel. The BHD6T and C60MC12 thin-film transistors showed high field-effect mobilities of 0.035 and 0.057 cm2/Vs, respectively. The complementary inverter with a supply voltage of 50 V exhibited inverting voltages of 26.8 V for forward and 27.0 V for backward sweeps and a high gain of 76.

In the Long-Term Evolution (LTE)-Advanced downlink, a user-specific demodulation reference signal (DM-RS) is used to support channel estimation and data demodulation for user-transparent multi-antenna and/or multi-point (MA/P) transmission techniques. A hybrid code division multiplexing (CDM) and frequency division multiplexing (FDM) scheme is adopted as a DM-RS multiplexing scheme for up to eight data streams per user. A time-domain orthogonal cover code (OCC) is used for CDM since time domain orthogonality among OCCs offers good robustness against channel variation. However, in a medium-to-high mobility environment, orthogonality distortion occurs among OCCs, which results in performance degradation. In this paper, we propose a two-dimensional (2D)-OCC mapping that achieves two-dimensional orthogonality in the time and frequency domains to improve the performance of CDM-based DM-RSs while reducing the peak transmission power of the OFDM symbol which includes the DM-RSs. Simulation results show that the proposed 2D-OCC mapping is effective in improving the block error rate performance especially in medium-to-high mobility environments. Furthermore, it is shown that the 2D-OCC mapping effectively reduces the peak power compared to the time-domain OCC mapping.

The accurate and fast estimation of link price is the key component of network-based congestion control schemes. A fast estimation method A2DPM is presented. Multiple hashes on IP identifier of packet header are adopted to accelerate the side information transmission, so accurate estimation of maximum price on the flow forwarding path can be realized after the receipt of just a few probe packets, and the sender is capable of reacting to congestion more quickly, making it suitable to meet the demands of dynamic networks.

In this paper, a low complexity hybrid smart antenna system with directional elements and reduced-size digital beamformer is proposed to combat the inter-symbol interference (ISI) problem over frequency-selective fading channel. For the conventional smart antenna system with omni-directional elements, it utilizes the full-size digital beamformer to suppress interference and obtain the optimum performance. However, the proposed hybrid smart antenna system with directional elements can be split the linear array receiver for two branches. One branch is the subarray system with non ISI interference, which can be used for maximum ratio combiner (MRC). Another branch is the reduced-size subarray system with the ISI interference, which can use the reduced-size optimum beamformer to suppress interference. Finally, the output signals of the two branches can be combined to detect the transmitted signals. Simulation results confirm that the proposed low complexity system can provide robust performance under the multipath fading channel.

The aim of this study is to improve the accuracy of flicker parameters estimation in old film sequences in which moving objects are present. Conventional methods tend to fail in flicker parameters estimation due to the effects of moving objects. Our proposed method firstly utilizes an adaptive Gaussian mixture model (GMM)-based method to detect the moving objects in the film sequences, and combines the detected results with the histogram-matched frames to generate reference frames for flicker parameters estimation. Then, on the basis of a linear flicker model, the proposed method uses an M-estimator with the reference frames to estimate the flicker parameters. Experimental results show that the proposed method can effectively improve the accuracy of flicker parameters estimation when the moving objects are present in the film sequences.

We propose a two-phase diversity scheme to achieve the end-to-end spatial diversity gain for physical-layer network coding (PNC) based two-way relay with a multiple-antenna relay node. A novel binary PNC-specific maximal-ratio-combining like (MRC-L) scheme is proposed to obtain receive diversity in the multiple-access (MA) phase with linear complexity; the Max-Min criterion based transmit antenna selection (TAS) is adopted to obtain transmit diversity in the broadcast (BC) phase. Both the brief diversity analysis and the Monte Carlo (MC) simulation results demonstrate that the proposed scheme achieves full diversity and outperforms other comparable schemes in terms of end-to-end diversity or power advantage.

The noise performance of common source and cascode topology 60 GHz LNAs is analyzed and verified. The analysis result shows that the noise performance of the cascode topology is degraded at high frequency due to the inter-stage node capacitance. The analysis result is verified by experimental results. A three-stage LNA employing two noise-matched CS stages and a cascode stage is proposed. For comparison a conventional two-stage cascode LNA is also been studied with the measurement-based model. The measured results of the proposed LNA show that an input and output matching of less than -10 dB, a maximum gain of 9.7 dB and a noise figure (NF) of 3.2 dB are obtained with a power consumption of 30 mW from a 1.2-V supply voltage. Compared to the conventional cascode LNA, an improvement of 2.3-dB for NF and 1.9-dB for power gain are realized. Both the proposed and conventional LNAs are implemented in 65 nm CMOS process.

The cooperative relay network exploits the space diversity gain by allowing cooperation among users to improve transmission quality. It is an important issue to identify the cluster-head (or relay node) and its members who are to cooperate. The cluster-head consumes more battery power than an ordinary node since it has extra responsibilities, i.e., ensuring the cooperation of its members' transmissions; thereby the cluster-head has a lower throughput than the average. Since users are joining or departing the clusters from time to time, the network topology is changing and the network may not be stable. How to balance the fairness among users and the network stability is a very interesting topic. This paper proposes an adaptive weighted clustering algorithm (AWCA), in which the weight factors are introduced to adaptively control both the stability and fairness according to the number of arrival users. It is shown that when the number of arrival users is large, AWCA has the life time longer than FWCA and similar to SWCA and that when the number of arrival users is small, AWCA provides fairness higher than SWCA and close to FWCA.

We determine the autocorrelations of the quaternary sequence over F4 and its modified version introduced by Du et al. [X.N. Du et al., Linear complexity of quaternary sequences generated using generalized cyclotomic classes modulo 2p, IEICE Trans. Fundamentals, vol.E94-A, no.5, pp.1214–1217, 2011]. Furthermore, we reveal a drawback in the paper aforementioned and remark that the proof in the paper by Kim et al. can be simplified.

In this paper, an active control scheme is designed for the hybrid direct methanol fuel cell (DMFC) system to achieve the following three objectives simultaneously: (i) maximize the power produced by the DMFC stack in the stable operation as high loading (for avoiding the operation of DMFC in diffusion region), (ii) keep the power produced by the DMFC stack with the high efficiency as low loading, (iii) prevent the problem of methanol crossover at a very low load. Considering the characteristics of DMFC stack during actual operation, the states VP (t) and P (t) are utilized as the linguistic variables. Also considering the fuel efficiency of DMFC stack ηfuel as the linguistic variable, the active control scheme is designed to achieve the above multiple objectives. To clarify the reliability and stability of the proposed control scheme, an experiment is performed. Its results show that the proposed control scheme can achieve above multiple objectives efficiently.

In order to detect snow and ice on a road surface, the microwave measurement method of dielectric constants are presented. And some examples of measurements for artificial and natural snow and ice using the method are introduced. The results show reasonable estimations of the dielectric constants, and they indicate that the method could be utilized for the snow and ice detection.

The fixed points of the belief propagation decoder for non-binary low-density parity-check (LDPC) codes are referred to as stopping constellations. In this paper, we give the stopping constellation distributions for the irregular non-binary LDPC code ensembles defined over the general linear group. Moreover, we derive the exponential growth rate of the average stopping constellation distributions in the limit of large codelength.

This letter proposes a novel technique for detecting a target signal buried in clutter using principal component analysis (PCA) for pulse-Doppler radar systems. The conventional detection algorithm is based on the fast Fourier transform-constant false alarm rate (FFT-CFAR) approaches. However, the detection task becomes extremely difficult when the Doppler spectrum of the target is completely buried in the spectrum of clutter. To enhance the detection probability in the above situations, the proposed method employs the PCA algorithm, which decomposes the target and clutter signals into uncorrelated components. The performances of the proposed method and the conventional FFT-CFAR based detection method are evaluated in terms of the receiver operating characteristics (ROC) for various signal-to-clutter ratio (SCR) cases. The results of numerical simulations show that the proposed method significantly enhances the detection probability compared with that obtained using the conventional FFT-CFAR method, especially for lower SCR situations.

We propose a novel background and foreground estimation algorithm in MAP-MRF approach for binarization of degraded document image. In the proposed algorithm, an assumption that background whiteness and foreground blackness is not employed differently from the conventional algorithm, and we employ character's irregularities based on local statistics. This makes the method possible to apply to the image with various colored characters, ex. outlined characters by colored background. The effectiveness and the validity are shown by applying the proposed method to various degraded document images.

This letter considers a sum-rate maximization problem with user scheduling wherein each user has a minimum-rate requirement in multiple-input-multiple-output broadcast channel. The multiuser strategy used in the user scheduling is a joint transceiver scheme with block diagonal geometric mean decomposition. Since optimum solution to the user scheduling problem generally requires exhaustive search, we propose a suboptimum user scheduling algorithm with each user's minimum-rate requirement as the main constraint. In order to satisfy maximum sum-rate and minimum-rate constraints simultaneously, we additionally consider power allocation for scheduled users. Simulation results show that the proposed user scheduling algorithm, together with the user power allocation, achieves sum-rate close to the exhaustive search, while also guarantees minimum-rate requirement of each user.

In non-cooperative scenarios, the estimation of direct sequence spread spectrum (DS-SS) signals has to be done in a blind manner. In this letter, we consider the spreading sequence estimation problem for DS-SS signals. First, the maximum likelihood estimate (MLE) of spreading sequence is derived, then a semidefinite relaxation (SDR) approach is proposed to cope with the exponential complexity of performing MLE. Simulation results demonstrate that the proposed approach provides significant performance improvements compared to existing methods, especially in the case of low numbers of data samples and low signal-to-noise ratio (SNR) situations.