- EI核心期刊
In traditional subcarrier allocation algorithms, the problem of unfairness between the celledge users and cellcenter users and varying power allocation in downlink coordinated multiple point transmission/reception (CoMP) system is ignored. To solve this problem, a suboptimal subcarrier and power allocation algorithm to maximize all the users throughput in one sector is proposed. In this algorithm, the frequency bandwidth that the celledge users can occupy is extended to the whole frequency bandwidth that the BS (base station) assigns to the cell, the cellcenter users and celledge users compete for the optimal subcarrier through the proportional fairness algorithm which will ensure the fairness. Then according to the optimization objective function and the proposed subcarrier allocation algorithm, the minimum rate and the proportional fairness constraint are introduced in connection to all the users. At last, the power allocated to each user is calculated using the Lagrange multiplier method. Simulations show that this algorithm will improve all the users fairness and throughput obviously.
A new routing algorithm named spray and wait routing algorithm based on grey Markov prediction model (SWR-GM) for delay tolerant network (DTN) is proposed. It combines grey Markov location predicting model with the spray and wait routing algorithm depending on activity coefficient of a node (ACoN). It predicates the location of the destination node by utilizing grey markov location predicting model. It also introduces the concept of ACoN to quantify the strength of a nodes activity. In addition, the algorithm sprays and forwards packets on the basis of ACoN, so it can enhance the transfer direction. Simulation shows that SWRGM algorithm can provide better network performance compared with the Epidemic algorithm and the traditional spray and wait outing (SWR) algorithm.
The design and optimization method of a spherical underwater vehicle BYSQ-2's structure is presented. The vehicle's attitude can be changed by the inner steering mechanism. The structure of the vehicle is designed according to the configuration scheme and design index. After the thruster's type is chosen, the size of the pipe's inside diameter can be optimized by the admiralty coefficient law. According to the whole machine balancing law, the structure is adjusted to achieve symmetry, and the counterweight's quality is optimized. The BYSQ-2’s prototype is manufactured according to the conclusion, and the result of the experiment indicates that the prototype's performance achieves the design requirement.
A new ultra-wideband electromagnetic bandgap (EBG) structure is proposed for simultaneous switching noise suppression (SSN). A analysis and design of the bandgap properties of the new EBG structure is given, the characteristics of stopband and signal integrity are simulated, showing that the new EBG's stopband is improved, and the lower cut-off frequency is decreased comparing with the Z-bridged EBG structure with the same parameters. Meanwhile, signal integrity of the proposed EBG power plane can be improved by using differential transmission lines.
In the smoky, foggy, hazy and other harsh outdoor conditions, scene image captured is severely degraded by the scattering of atmospheric particles. Based on atmospheric scattering model, the degraded image needs a white balance operation to simplify the atmospheric scattering model; then, a new nonlinear spatial filtering algorithm is put forward to estimate the rough luminance of the sky, and joint bilateral filter is introduced to further refine the luminance of the sky. Finally, image is restored by using tone mapping. The complexity of the proposed algorithm is only a linear function of the input image pixels numbers, and this allows a very fast implementation. Experiments show that the proposed algorithm can effectively restore the fogdegraded images. With this algorithm, the images is restored with more natural, realistic, and higher-definition.
The features of social media, such as node influence are important in information prediction. A new model with attribute, number and views of nodes (ANV) is proposed for event prediction. Experiment is designed to predict the performance of new released movies using back propagation (BP) neural network algorithm with the data of Sina Microblog. Compared to other models, when considering the node attribution, the proposed has higher prediction accuracy.
One of the key points of the MPEG-4 standard is the possibility to access and manipulate objects within a video sequence, but it increases the demand for information security protection and multimedia authentication technologies. An object based watermarking algorithm is proposed, which can correctly access the data embedded in the object. To resist against scaling and rotation attacks, two generalized Radon transformations are used. The watermark is embedded in the quantized SA-DCT coefficients. Experiments show that the algorithm is lowdistortion, robust to geometry transformation attacks. And the algorithm can integrate with the MPEG-4 codec very well.
Considering the Internet of things based on radio frequency identification (RFID) as the study object and using the multiple ON-OFF traffics model (obeys heavy tail distribution of Pareto), a centralized self similar layered traffic model of Internet of things is proposed in view of its structure and traffic characteristics. The validity of the model is verified through the measurement of selfsimilarity parameter. Simulation proves that the model is effective. Moreover, the selfsimilarity increases network packet loss rate and queuing delay, and reduces the system throughput.
A new modulation recognition method of the subcarriers with pilots for orthogonal frequency division multiplexing (OFDM) signals is proposed. The method firstly identifies null subcarrier signals of the OFDM and the pure pilot subcarrier signals by combination features of higher order cumulants in the equivalent model of OFDM. Then, it recognizes the modulated subcarrier signals which are less affected by pilots using comparing the variance of sequences in the minimum ring of vectogram. Simulation shows that the proposed method is effective and feasible in the multipath channels.
To solve the problem of unevenness in energy consumption which tends to cause the network disconnection in stripbased wireless sensor networks, a improved topology control algorithm and sleep-awake scheme is proposed. Based on the set clustering, the clusterhead nodes are periodically elected under a migrationbased scheduling mechanism designed to regulate nodes duty cycles as well as intra/intercluster communication distances. And the load balance of them is achieved by adaptively adjusting the listening schedule. Simulations show that this algorithm could effectively prolong the network lifespan and improve the network completeness of the sensing area in the later period.
Aiming that the optimal solution of dynamic resource allocation in relay networks is still incomplete, and combining the information theory with effective capacity, an optimal solution of dynamic resource allocation in estimateandforward (EF) relay networks is given independently. Moreover, setting the typical network as an example, a selfadaptive relay networks scheme based on dynamic resource allocation is put forward. A dynamic choice can be availed within three relay protocols, that can be depicted as amplifyandforward (AF), decodeandforward (DF) and EF according to the system QoS exponent requirement. Numerical simulation indicates that the dynamic resource allocation scheme can effectively maximize the effective capacity of relay networks under the limitation of system QoS exponent. Furthermore, the selfadaptive relay network scheme can improve a much better throughput performance than the traditional monorelay scheme.
In order to reduce decoding complexity for 8×8 semiorthogonal algebraic spacetime code (SAST), a new encoding and decoding method is proposed for 8×8 SAST code with QAM modulated signals. In the proposed method, through part of the transmitted signals rotated by a certain angle according to the feedback information, the real part and the imaginary part of the first half and the second half of the transmitted signal vectors are mutually orthogonal. So its decoding complexity is proportional to the square of the modulation order. Simulation shows that the decoding complexity is reduced greatly by the proposed code only with 5 bit feedback.
The introduction of cyclic shift delay (CSD) is used in IEEE 802.11n to distinguish different spatial streams, however it poses a challenge to synchronization. The traditional synchronization methods, which utilize the crosscorrelation between the local training sequence and the received signal, will cause many spurious peaks and result in deteriorated synchronization performance. A new joint symbol synchronization and fine frequency offset estimation algorithm is proposed. It exploits the structure of IEEE 802.11n preamble and adopts a delaycorrelation algorithm to eliminate the effect of CSD. The proposed algorithm has advantages in avoiding the effect of carrier frequency offset, suppressing the generation of spurious peak results and improving the detection accuracy.
Considering the difficulty in classifying quadrature amplitude modulation (MQAM) signals over rayleigh fading channel, an algorithm based on antenna arrays for identifying MQAM signals in Rayleigh fading channels is presented. The characteristic that spatial diversity reception can improve the SNR of received signals is used. First, the equal gain diversity model for modulation classification is given. Then, the nonlinear leastsquares estimator is presented to estimate the frequency offsets and phase offsets. Finally the normalized fourthorder and sixthorder cumulants of the signal at the output of the combiner are estimated, that can be used as modulation classification features. Simulations demonstrate that the proposed scheme is efficient in rayleigh fading channel. Compared to the existing quasi hybrid likelihood ratio test (qHLRT) method, the proposed method has lower computational complexity and stronger practicability.
An adaptive backoff algorithm based on transmission state (ABTS) for Ad Hoc network is proposed. Used with ABTS, the channel status is sensed by calculating amount of competitive nodes locally and the contention window is adjusted linearly or multiplicatively according to different channel status. To reduce data losses, ABTS algorithm gives frames retransmitted repeatedly higher priority to send. Experiment demonstrates that ABTS algorithm has suitable performances in multi-hop Ad Hoc network, and, compared to Binary Exponential Backoff algorithm, ABTS algorithm has better performances in term of throughput, endtoend delay and collision rate.
An estimating and monitoring model of software project schedule is studied based on significant deviation standard. According to the principle of process control, dynamic control of software project effort based on significant deviation standard and risk reserve time is put forward as well. Three methods are introduced aimed on how to define significant deviation standard. They provide the foundation to improve the accuracy of project management and ensure the completion of projects within acceptable deviation.
A new measurement for highprecision time interval is provided to satisfy the present precision requirement of the time synchronization. Utilizing the own periodicity of 1pps signals, the multi-level time interval measurement and correction is put forward to keep time synchronization, in which the measured time interval is high-precisely measured and corrected under different time interval conditions. Experiment shows a ±24ps resolution and accuracy is reached.
The system capacity of conventional multicast transmission in wireless system is limited by the worst user in the multicast group. A resource allocation algorithm for multicast system is proposed to overcome the capacity limitation by exploiting the multiuser diversity. Each subcarrier is allocated to some users with good channel state information. Due to the nonconvex property of the power allocation, power allocation based on gradient is adopted to optimize the power allocation locally. Simulation shows that the transmission rate is significantly improved by using our proposed algorithms, when compared to the traditional multicast transmission scheme.
A video decoding dependency erasure code is proposed to reduce receivers video delay in wireless video broadcast. According to packet receiving status of broadcast receivers, the proposed coding scheme first considers video packets decoding dependency, and then constructs coded packets on the fly to reduce receivers video delay. Simulation shows that the proposed code has lower video delay than the existing erasure codes.
In the existing MapReduce framework, the single master is the performance bottleneck. As a result, the size of the cluster is limited. In order to break the bottleneck, a multimaster framework is proposed in this paper. The implementation is based on Apache Hadoop MapReduce. The main framework and signaling system are redesigned to sustain more than one master. Meanwhile a doublemaster hot backup scheme is designed to solve single master failure, so that the new framework is able to reduce the impact of master failure.
Three priori information aided SNR estimation algorithm is proposed based on maximum likelihood sequential criterion. Compared with the existing harddecision aided SNR estimation algorithm, the proposed algorithm decreases estimation error in low SNR state. The performance of the algorithm in the beginning of iteration and in the next iterations in turbo equalizer is analyzed. According to different number of iteration, switching one algorithm to another can raise the estimation precision, and lower complexity. The new algorithms only use small number of data symbols, they can also handle a large range of SNR.
A three-limb robot with integrated of armleg mechanism is developed based on functional bionics. The robot can accomplish locomotion and operation tasks in time sharing multiplex mode with aid of permanent magnet absorption mechanisms and operation mechanisms mounted on each limb, and has a variety of agile walking gaits and operation patterns as well. Experiments of fundamental walking gaits and objects operation shows practicality.
To improve energy efficiency in cooperative relay system, an approach to optimize the energy consumption of cooperative hybrid automatic repeat request (HARQ) protocols with adaptive modulation over Nakagami-m fading channel is proposed. Through modeling the state transition diagram, the total energy consumption and outage probability performance are derived. Further, an optimization framework to minimize the total energy consumption is formulated, and an exhaustive search algorithm is presented. It is shown that the performance of cooperative HARQ is better than the noncooperative HARQ. In addition, the proposed crosslayer scheme can reach to about 80% energy savings over the nonoptimized system.
A partial network coding scheme is proposed for wireless sensor network based on the eventdriven, it can meet highefficiency, lowpower transmission in the case of partial nodes participating in the encoding. The encoding nodes are categorized into the business encoding nodes and capability encoding nodes based on the heterogeneity of sensor nodes and the eventdriven way, increasing the robustness of the network coding and improved the efficiency of network coding. Simulation shows that this scheme is superior to the traditional network coding scheme in energy consumption, network throughput and transmission delay.
A gradient projection method combining Barzilai-Borwein stepsize and nonmonotone line search is proposed and applied to signal reconstruction in compressive sensing. The computation of Barzilai-Borwein stepsize is analyzed, A corresponding nonmonotone line search method is introduced. To reduce influence of line search, an adaptive nonmonotone line search is designed. Convergence analysis of the algorithm is given. Experiment shows that the proposed algorithm can get good performances of signal reconstruction with different sparsity, seems better than Basis Pursuit, Orthogonal Matching Pursuit and other gradient projection algorithms.
An improved bit-flipping (BF) algorithm with low complexity for decoding structured lowdensity parity-check codes (LDPC) is proposed to improve the performance of the harddecision BF algorithm. The harddecision bits are divided into two groups based on the magnitudes of the received symbols, and at each iteration, the proposed algorithm can flip more than one bit with using two thresholds, and the flipping error probability is effectively decreased. The improved BF algorithm requires some real number comparisons before iterations and requires only logical operations during the iterations. Compared with the weighted bitflipping algorithm and its modifications, the new method is with significantly lower complexity. Simulations show that the proposed algorithm is provided with very fast convergence speed and excellent performance with significantly low complexity.
Aiming at the noise sensitivity of blind source separation for mixed images based on the clustering sparse component analysis, a blind source separation method for mixed images with additive white Gaussian noise is proposed. The noise intensity in mixed image is evaluated by correlation coefficients between mixed image and noise image, then via sparse component analysis, the original images are separated from denoising mixed images. Experiment shows that the presented algorithm can remove the noise effectively, and extract the original images accurately from overlying noise mixed images.
A top-down and depth-first algorithm is proposed for horizontally merging concept lattices. The influences of the inserting order of the parents/children concepts on new concepts and updated concepts are investigated. Some theorems on inserting and updating concepts are proved. Based on this, a recursive traversal order is designed to insert concepts into lattices, which can drastically reduce the number of concepts comparisons. Experiment and analysis indicate that the proposed algorithm can obviously improve efficiencies compared with other concept lattices merging algorithms.