To decrease memory access of the decoder for double binary convolutional turbo code (DB CTC), an iterative decoding scheme is proposed. Instead of accessing all of the backward state metrics from the state metric cache (SMC), a part of them is computed by the recalculation unit (RU) in the forward direction. By analysis and simulations, both the amount of memory access and the size of SMC are reduced by about 45%. Moreover, combined with the scaling technique, the proposed scheme gets decoding performance near to that of the well-known Log-MAP algorithm.

The need for real-time use of human dynamics data is increasing. The technical requirements for this include improved databases for handling a large amount of data as well as highly accurate sensing of people's movements. A bitmap index format has been proposed for high-speed processing of data that spreads in a two-dimensional space. Using the same format is expected to provide a service that searches queries, reads out desired data, visualizes it, and analyzes it. In this study, we propose a coding format that enables human dynamics data to compress it in the target data size, in order to save data storage for successive increase of real-time human dynamics data. In the proposed method, the spatial population distribution, which is expressed by a probability distribution, is approximated and compressed using the one-pixel one-byte data format normally used for image coding. We utilize two kinds of approximation, which are accuracy of probability and precision of spatial location, in order to control the data size and the amount of information. For accuracy of probability, we propose a non-linear mapping method for the spatial distribution, and for precision of spatial location, we propose spatial scalable layered coding to refine the mesh level of the spatial distribution. Also, in order to enable additional detailed analysis, we propose another scalable layered coding that improves the accuracy of the distribution. We demonstrate through experiments that the proposed data approximation and coding format achieve sufficient approximation of spatial population distribution in the given condition of target data size.

Green cognitive radio (CR) plays an important role in offering secondary users (SUs) with more spectrum with smaller energy expenditure. However, the energy efficiency (EE) issues associated with green CR for fading channels have not been fully studied. In this paper, we investigate the average EE maximization problem for spectrum-sharing CR in fading channels. Unlike previous studies that considered either the peak or the average transmission power constraints, herein, we considered both of these constraints. Our aim is to maximize the average EE of SU by optimizing the transmission power under the joint peak and average transmit power constraints, the rate constraint of SU and the quality of service (QoS) constraint of primary user (PU). Specifically, the QoS for PU is guaranteed based on either the average interference power constraint or the PU outage constraint. To address the non-convex optimization problem, an iterative optimal power allocation algorithm that can tackle the problem efficiently is proposed. The optimal transmission powers are identified under both of perfect and imperfect channel side information (CSI). Simulations show that our proposed scheme can achieve higher EE over the existing scheme and the EE achieved under perfect CSI is better than that under imperfect CSI.

Pulse Pairs (PPs) generated by Distance Measure Equipment (DME) cause severe interference on L-band Digital Aeronautical Communication System type 1 (L-DACS1) which is based on Orthogonal Frequency Division Multiplexing (OFDM). In this paper, a novel and practical PP mitigation approach is proposed. Different from previous work, it adopts only time domain methods to mitigate interference, so it will not affect the subsequent signal processing in frequency domain. At the receiver side, the proposed approach can precisely reconstruct the deformed PPs (DPPs) which are often overlapped and have various parameters. Firstly, a filter bank and a correlation scheme are jointly used to detect non-overlapped DPPs, also a weighted average scheme is used to automatically measure the waveform of DPP. Secondly, based on the measured waveform, sparse estimation is used to estimate the precise positions of DPPs. Finally, the parameters of each DPP are estimated by a non-linear estimator. The key point of this step is, a piecewise linear model is used to approximate the non-linear carrier frequency of each DPP. Numerical simulations show that comparing with existing work, the proposed approach is more robust, closer to interference free environment and its Bit Error Rate is reduced by about 10dB.

Machine vision-based automatic anti-bird thorn failure inspection, instead of manual identification, remains a great challenge. In this paper, we proposed a novel Object Position Embedding Network (OPENnet), which can improve the precision of anti-bird thorn localization. OPENnet can simultaneously predict the location boxes of the support device and anti-bird thorn by using the proposed double-head network. And then, OPENnet is optimized using the proposed symbiotic loss function (SymLoss), which embeds the object position into the network. The comprehensive experiments are conducted on the real railway video dataset. OPENnet yields competitive performance on anti-bird thorn localization. Specifically, the localization performance gains +3.65 AP, +2.10 AP50, and +1.22 AP75.

It is interesting to resolve coherent signals impinging upon a linear sensor array with low computational complexity in array signal processing. In this paper, a computationally efficient method of signal subspace fitting (SSF) for direction-of-arrival (DOA) estimation is developed, based on the multi-stage wiener filter (MSWF). To find the new signal subspace, the proposed method only needs to compute the matched filters in the forward recursion of the MSWF, does not involve the estimate of an array covariance matrix or any eigendecomposition, thus implying that the proposed method is computationally efficient. Numerical results show that the proposed method provides the comparable estimation accuracy with the classical weighted subspace fitting (WSF) method for uncorrelated signals at reasonably high SNR and reasonably large samples, and surpasses the latter for coherent signals in the case of low SNR and small samples. When SNR is low and the samples are small, the proposed method is less accurate than the classical WSF method for uncorrelated signals. This drawback is balanced by the computational advantage of the proposed method.

Secure access is one of the key concerns of wireless sensor networks (WSNs). In WSNs, because there are many dynamically mutable attributes, continuous access decisions and dynamic attribute updates should be important properties of access control. In addition, WSNs need low-complexity authentication protocols because of the constrained resources. However, the authentication protocols of most current security access schemes have relatively high complexity. More importantly, the access control models of existing schemes cannot provide attribute mutability and continuous decisions dynamically. To address above issues, we propose a dynamic secure access mechanism for WSNs. Firstly, we design a lightweight secure authentication protocol and dynamic access control based on security token and usage control (UCON), respectively. Then, the agent technology is adopted to implement the proposed secure access scheme. Secondly, we analyze the probability of the dynamic attribute update and decisions. Thirdly, we implement an instance of UCON. The implementation results indicate the feasibility of using UCON in WSNs. Finally, by evaluating and comparing with current schemes, the authentication protocol in our scheme presents several advantages including the low expenses in calculation, storage and communication. To our best knowledge, this paper is the first to realize next generation dynamic access control with attribute mutability and continuous decisions in WSNs.

In an Orthogonal Frequency Division Multiplexing (OFDM) systems, the Peak to Average power Ratio (PAR) is high. The clipping signal scheme is a useful and simple method to reduce the PAR. However, it introduces additional noise that degrades the systems performance. We propose an oversampling scheme to deal with the received signal in order to reduce the clipping noise by using finite impulse response (FIR) filter. Coefficients of the filter are obtained by correlation function of the received signal and the oversampling information at receiver. The performance of the proposed technique is evaluated for frequency selective channel. Results show that the proposed scheme can mitigate the clipping noise significantly for OFDM systems and in order to maintain the system's capacity, the clipping ratio should be larger than 2.5.

A novel adaptive algorithm based on pilot channel (PCA) for MMSE multiuser detection in downlink CDMA is proposed in this paper. This algorithm uses the information in pilot channel to compute the desired weight vector directly. Compared with conventional adaptive algorithms and blind algorithms, it does not require training sequences nor channel estimation. Analysis shows that the weight vector obtained by the PCA algorithm converges to the Wiener solution globally and its computational complexity is O(N2). Simulation results show that the PCA algorithm can adapt rapidly to the changing environment. The steady state performance can be enhanced by increasing the transmitted power in pilot channel, but is worse than that of conventional recursive least-square (RLS) algorithm in decision-directed mode. Also, performance of the adaptive MMSE detector is much better than that of conventional RAKE receiver.

For embedded systems, verifying both real-time properties and logical validity are important. The embedded system is not only required to the accurate operation but also required to strictly real-time properties. To verify real-time properties is a key problem in model checking. In order to verify real-time properties of assembly program, we develop the simulator to propose the model checking method for verifying assembly programs. Simultaneously, we propose a timed Kripke structure and implement the simulator of the robot's processor to be verified. We propose the timed Kripke structure including the execution time which extends Kripke structure. For the input assembly program, the simulator generates timed Kripke structure by dynamic program analysis. Also, we implement model checker after generating timed Kripke structure in order to verify whether timed Kripke structure satisfies RTCTL formulas. Finally, to evaluate a proposed method, we conduct experiments with the implementation of the verification system. To solve the real problem, we have experimented with real microcontroller software.

The effect of NiP as a seed layer for the [Co/Pd]n multilayer perpendicular recording media was studied. It was found that a thin layer of 2 nm NiP inserted between the FeCoC soft magnetic underlayer and the [Co/Pd]n recording layer improved the magnetic properties such as coercivity, squareness and nucleation field. These improvements may be due to the enhanced grain isolation promoted by the NiP seed layer, as well as the lower surface roughness of the NiP seed layer. Read/write test using Guzik spin stand with a ring-type head showed a D50 value 220 kFCI in the roll-off curve. The magnetic transitions recorded up to 390 kFCI for [Co/Pd]n media with the NiP seed layer can be observed clearly with MFM.

A Co/Pd multilayer film with perpendicular coercivity of 2.2 kOe and remanence ratio (SQ) of unity was prepared by electron beam evaporation in vacuum. In the MFM image of signal patterns of 4 kFRPI recorded using a ring-type MIG head, many reversed domains were observed. However, when the film was magnetized along the film normal direction using an electromagnet (H = -13 kOe), only few reversed magnetic domains were observed, which was consistent with SQ = 1. Therefore, the reversed domains in the signal patterns were induced in the recording process. dc erasing was also studied with the magnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular component of the field was kept constant while the in-plane component was varied, implying that the in-plane field component did not contribute to the formation of the reversed domains. It was found that reversed magnetic domains were easily induced even by a weak reversing magnetic field applied along the film normal. Hence, although the possibility of an insufficient recording head field was not excluded, it seemed more likely that the reversed magnetic domains in the signal patterns were caused by some erasing effect of the ring-type MIG head. For a Co/Pd multilayer medium with a negative nucleation field in the perpendicular M-H loop, a stronger reversing field was needed to induce the reversed magnetic domains. No reversed magnetic domains were observed in the MFM image for signal patterns of 4 kFRPI in this medium, indicating that a negative nucleation field was effective to suppress the formation of reversed magnetic domains.