- EI核心期刊
An adaptive subcarrier and power allocation scheme based on limited feedback for multicast relay networks is proposed. The new scheme works in three steps. Firstly, transfer mode of each multicast group is determined using a new feedback algorithm and transfer protocol. Secondly, a fair subcarrier allocation scheme is proposed to achieve a tradeoff between fairness and qualityofservice. Finally, a new cooperative power iterative scheme is introduced to allocate power effectively, where target rate on each subcarrier is computed by waterfilling algorithm in the first place and then a power iterate process is implemented to optimize power allocation. Simulations show that the new scheme significantly reduces feedback overhead. Moreover, both the required power and the multicast service outage of the scheme are much less than those of the direct scheme.
The transmit beamforming algorithm design of cognitive radio (CR) network is studied.In order to guarantee the quality of service， the optimization is formulated to minimize the CR network transmit power under the constraint of outage probability at the CR users and primary users. Simulations show that with the knowledge of assumed statistical distribution of channel covariance error at the transmitter， this scheme can effectively minimize the transmit power of each CR user， enhance the CR network performance and decrease the interference to primary user.
A new S/G/m/FCFS queuing model for GPON system is proposed to analyze the access delay for dynamic bandwidth allocation algorithms. An evaluation for both Static Estimation Bandwidth allocation (SEBA) and Dynamic Estimation Bandwidth allocation (DEBA) are carried out based on the proposed queuing model. To save bandwidth resource and improve network performance, the estimation factor of DEBA can be adjusted dynamically according to the traffic load. Simulations verify that DEBA is superior to SEBA for obtaining lower access delay and mitigating congestion effectively.
Used in video sequences, an algorithm for multifeature particle filter (PF) is put forward with resampling. The new CamShift is applied to each particle in order to make all particles reach a stable position nearby. Likelihood function for each particle is computed by color and edge Bhattacharyya coefficients. The method exploits the CamShift characteristic of low computational complexity, which makes PF realize target tracking by less particles than before. Analysis shows that the method is robust to occlusion.
Cooperative spectrum sensing based on energy probability distribution (EPD) is proposed to improve the sensing performance of the cognitive radios. Instead of averaging the energy in the traditional energy detection scheme, each cooperative secondary user in the EPD scheme records the number of the received samples, its energy is over a given threshold. Correlation between the sum of the recorded numbers and the EPD of the noise is used at the data fusion center to reach a final decision. Gaussian approximation is used to analyze the performance of the proposed EPD spectrum sensing method. Simulation demonstrates that with the increase of cooperative users, the proposed scheme is of better performance than the traditional cooperative onebit hard spectrum sensing. No prior information is required in the proposed scheme.
A network control method for multipath transfer is proposed.The decision function is placed on the network side. The waiting time for reordering is estimated for each packet according to its arrival state. The transmission control decision is made based on the estimated time value. Simulation indicates that the proposed method can reduce the reordering delay effectively especially in the scenario of more than two bearers.
Tradeoff between diversity and rate in space frequency block codes (SFBC) is adopted, and embedded SFBC is proposed. The information is divided into the based stream and the enhanced stream. The based stream is received in bad channel, but the based and enhanced are received simultaneity in good channel. The transmission rate can be improved, and it is ensure that the based information stream is received reliably. Meanwhile, the peak average ratio formulation of our proposed codes is derived in two transmission antennas. Simulations show that the based information of embedded SFBC could have higher diversity order than Alamouti SFBC in lower signal to noise ratio. Compared with the opportunistic space time block codes, the proposed space frequency codes is of lower bit error ratio of system when used 2 transmission antennas under high Doppler shift conditions.
For influenced by calibration source, the reflection coefficient of microwave radiometer receiver is studied to improve the accuracy of the microwave radiometer. The error calculation formula and system noise formula are also provided. Utilizing 3165 GHz microwave radiometer to certify the inverse radiation of calibration source, it is shown that the reflection coefficient is influenced by inverse radiation. Therefore, the missmatch factor and the system noise increasing are influenced by reflection coefficient.
A focus on the degree of influence of different factors and the relationship between these influence factors is studied based on refined and explained the influencing factors of development of Chinese telecommunications industry intellectual property. The hierarchical relations of different influencing factors with interpretative structural modeling(ISM) is analyzed.
Based on minimum mean square error of detected signal at destination node, a new transfer matrix design algorithm is proposed to improve the performance of multiple input multiple output (MIMO) relay communication systems. A major purpose of this algorithm is to solve AX+XB=Ftype matrix equation. Through singular value decomposition method, the final optimal transfer matrix can be got at last. Linear precoding and linear detection based on zero forcing criterion is adopted owing to simplicity. Through algorithm analysis and simulation comparison, the ergodic capacity improvement margin is about 2 bit •s-1•Hz-1, better than the unitary matrix method under same simulation configuration．
In order to detect, diagnose and exclude potential or occurred faults on mobile devices, a useroriented detection mechanism is proposed. In the mechanism. A new UserBehavior Analysis model based on fuzzy math theory is firstly proposed to weigh the dependence degree of each service. Secondly, a UserBehavior Clustering Analysis model is introduced to divide mobile users into several clusters. Thirdly, integrations are made for the dependence degree of each service, the network status and failure rate of service into building a priority detectionservice set selection model. So the optimized sets for PreDetection of the service faults on mobile devices could be selected. Meanwhile, a UserBehavior Clustering Analysis Based Service Fault Detection Optimization Mechanism is implemented on a prototype system, and the optimal number of userclusters is validated judging by the average normal use ratio under three PreDetection scenarios.
A new audio blind watermarking scheme based on discrete wavelet transform discrete cosine transform singular value decomposition (DWTDCTSVD) is proposed. In this algorithm, the audio is split as blocks, and each block is decomposed on twodimensional DWT, then the approximate subband coefficients are decomposed on DCT, and the first quarter of the DCT coefficients are decomposed on SVD transform and get a diagonal matrix. At last, the watermarking information is embedded into the diagonal matrix. The watermark embedding capacity is 2756 bit/s. Experiments show that the algorithm can get better balance between transparency and robustness of watermark, and it has strong robustness against the common audio signal processing such as MP3 compression, requantization, resampling, lowpass filter, cutting replacement and additive white Gaussian noise.
In order to understand users’goals in web searching better, an approach which makes use of hierarchical dirichlet process (HDP) model to cluster the verbs of users’goals is proposed. Verbs are good indications of users’goal, and good verb clustering therefore causes good clustering of users’goals. Verbs of users’goals are represented by cooccurrence nouns and nouns that have dependency relations with the verb. Experiments show that HDP has better performance in verbs clustering than latent Dirichlet allocation and dirichlet process mixture model.
Aim at the problem that the channel state information (CSI) is not taken full advantage in traditional distributed generalized ABBA (GABBA) spacetime codes in amplifyandforward relay networks, an improved scheme is proposed. In this scheme, the receiver calculates and sends out the current feedback information according to the CSI. After receiving the feedback information at one of the relay nodes, some preprocess is used on the original signal of this branch. The scheme can alleviate the interference brought by channel dependence, and improve reliability of the system. Analysis and simulation result suggest that the proposed scheme can significantly decrease the system bit error rate in contrast with the former scheme at the cost of one bit feedback information.
In order to improve intelligence and self management capability of network, an autonomic management architecture for mobile selforganizing network is proposed. Their components and functions are analyzed in detail. The communication technology and load balance mechanism of management network are analyzed. And the autonomic management services are defined as well. They will enhance cooperation capability between management nodes from network level and business level. The feasibility of architecture and autonomic management services are also verified by typical selforganizing scenarios that a new added mobile network node is selfconfigured.
An adaptive distributed power allocation (DPPA) algorithm based on potential games is proposed. Subband capacity with penalty factor is raised as the utility function. A global optimization could be transformed into a local optimization problem with iteration. By means of gradient projection, the power could be adaptively allocated, and the intercell interference is restrained. As a result, the intercell interference coordination and reduction of time price are achieved. It is shown that the algorithm reduced the capacity loss effectively, while increasing the throughputs for celledge users.
A hybrid method for traffic splitting is proposed. It consists of calculating split ratio according to the ideal model and selecting optimal subnet of available links based on fuzzy multiple attributes decision making theory. The error between the split ratio is compared， and calculated by using ideal model and the transmission capabilities of all the links. A suitable method is adopted according to the comparative result. Simulation shows that the proposed can reduce reordering delay effectively for quality of service guarantee.
Considering intergroup fairness specifically, the problem of resource allocation for multiantenna multicast systems is studied, we formulate an optimization problem to maximize the system throughput given a set of available resources (power and subcarriers). A threestep algorithm is proposed, in which the multicast precoding process, subcarrier assignment and power allocation are operated separately to reduce the computational complexity. Simulation results also show that the system throughput is significantly improved by using the proposed algorithms both in multicast system and in unicast system.
Based on common used recursive maximum expansion method, a resource allocation method is proposed for clustered discrete Fourier transform spread orthogonal frequency division multiplexing (DFTsOFDM) systems in 3rd generation partnership project long term evolution (3GPP LTE)．Simulations show that, if the number of clusters for each user can be increased without considering the impact of peaktoaverage power ratio, the flexibility of resource allocation is increased, it will lead to a higher spectral efficiency of system．
In order to improve the sumcapacity of amplifyandforward scheme for twoway relaying over orthogonal frequency division multiple (OFDM), a subcarrier pairing method based on sorting the channel coefficients (SPSCC) with low complexity is proposed. And for jointing subcarrier pairing and its optimal power allocation, a resource allocation strategy is presented. The subcarrier pairing by applying SPSCC with equal power allocation among each subcarrier pair is firstly considered; and a dual decomposition for power allocation among each subcarrier pair with total power constraint is employed. Finally, the power of each subcarrier pair is allocated to each node，i.e. the optimal power allocation of each node is obtained. Numerical analysis shows that the proposed resource allocation strategy can improve the sumcapacity.
Network virus propagation is studied for 2D asynchronous cellular automata, and a network virus propagation model with time delay is proposed. The model effectively overwhelms the drawbacks of synchronous automata, and allows researchers to emulate virus propagation in networks on various congestion levels by simply adjusting the factor. It is shown that a hysteresis phenomenon occurs in the process of virus propagation due to time delay, with the overall trend unchanged.
To reduce the computational complexity of quality scalable video coding (SVC)， a three steps included fast mode decision algorithm is proposed. In the first step， skip modes which require little computational complexity are checked; afterwards， candidate modes are selectively searched according to the interlayer correlation; finally， the rest unchecked modes are calculated. If the minimal RateDistortion (RD) cost obtained in the first or the second step is smaller than the predefined threshold， early termination is trigged. Experiment demonstrate that， compared with the exhaustive search method， 459%808% encoding time can be saved by the proposed algorithm. The Peak Signal to Noise Ratio (PSNR) reduction is 025dB at most and the bit rate increment is 062% at most.
Extracting texture features of images with probability statistics models is a significant method of contentbased image retrieval. In order to overcome the shortcomings of lack of color information and improve probability statistics retrieval performance, an approach that combines the global dominant color and probability statistics is proposed. The combinative features including texture and color are utilized for second retrieval after linear weighting. Experiments based on the 2600 images database shows superior performance of our proposed method compared with the single feature image retrieval and the probability statistics retrieval, recall rates and average normalized modified retrieval rank have been raised by 30% and 22% respectively.
Mapping of the large scale emulation network topology to the physical devices of network testbed automatically is an nondeterministic polynomial hard problem because the best solution of network dividing is unresolvable. With high capability and similarity of the physical devices, which can for working out the approximate optimal solution of network dividing by improving the annealing algorithm, a method is presented. Besides, with the help of the information of network topology structure, this method can simplify the complexity of large scale emulation network topology on different network level by preprocessing. Experiment verifies that this method could improve the efficiency of network dividing and mapping.
Considering the channel time variant property in cooperative communication networks, a new system scheme is designed based on the system error probability. According to the encoding function, the error correct code with optimal hamming distance is chose for different channel in order to minimize the system error probability. Furthermore, the time variant power allocation algorithm is used to allocate the transmit power between the source node and relay node. Analysis and simulate show that the proposed scheme can obtain 07 dB improvement in frame error rate.
A new border gateway protocol (BGP) security problem, multiexitdiscriminator (MED) vulnerability, has been discovered, which could be abused in data hijacking. For the reason that BGP devices may not operate as expected with the extension of 4octet autonomous system (AS) number, data streams could be diverted to other Internet service providers unconsciously and bring serious threat to the global network. In addition the weakness is simulated under the environment of Cisco routers, and a kind of maninthemiddle data hijack based on the MED flaw is implemented and verified through the experiment.
The performances of nonbinary lowdensity paritycheck (LDPC) codes are studied and simulated on the presented noise burst channel model. Compared to binary LDPC codes, the nonbinary LDPC codes have a better antibursterror performance. The reason is given by analyzing the process of decoding. The transformation between binary soft information and nonbinary initial soft information is also presented. Simulations show that nonbinary LDPC codes have advantages of error performance and iterative characteristics with different parameters for noise burst channels.
The hybrid transmission scene involving both broadcasting link and relay link is considerd with channel estimation error. The bit error rate performance of amplifyandforward based transmission in reporting sensing data is analyzed. By deriving effective signal to noise ratio at the common receiver, the approximate expressions for average bit error rate is obtained. Simulations are further provided to confirm the analytical results.
Blind equalization is of advantage of high efficient data transmission rate and disadvantages such as complicated algorithms, complicated computations and slow convergences. Considering precoding single carrier systems with frequency domain equalization, a semiblind equalization method based on Bussgang algorithm is proposed. The error signal of this method is skillfully designed so that the similar Bussgang algorithm can be used. At the same time, its convergence speed becomes faster due to selecting initialization. The method can be implemented easily because it does not need complex inversion computation compared with the existing related method. Simulation shows that the proposed method outperforms the existing algorithm.