- EI核心期刊
On the basis of Chameleon hash and D.Boneh’s one round multi-party key agreement protocol, a multi-designated verifiers signature scheme was proposed. In the scheme, the signature can be verified independently by each of the n designated verifiers designated by the signer and no one else than the designated person can be convinced by this signature even if one of the designated verifiers reveals the secret value. The security analysis of the proposed scheme shows that it satisfies non-transferability, unforgeability, privacy of signer's identity and has low computational cost.
A new kind of texture image retrieval algorithm based on Radon and wavelet transform is presented. Firstly, the Radon transform is used to deal with retrieval image. Centering the Radon projection of image by its center of mass can eliminate the shift effect. The statistical value of projection can be used to normalize the projection matrix. Then the translation- , rotation- and scale-invariant wavelet coefficients of the projection can be attained by using a TSI wavelet transform along and t directions. Secondly, the energy of every sub frequency bands is extracted to be the texture feature of image. The Gaussian model is used to normalize the different sub-characters distance to the texture feature of image. Thirdly, the texture similarities of images are computed by the Canberra distance. The image retrieval experiments indicate that this method is robustness to the noises in image’s similarity retrieval and has a higher retrieval-rate than other methods’.
To solve the difficult problem of long probing delay and inaccurate probing results in endpoint admission control method, a joint local and end-to-end admission control algorithm is proposed, which introduces local probing of access network besides end-to-end probing. Through local probing, the algorithm accurately estimates resources status of access network. We show through simulation that this algorithm can improve admission control performance and reduce users’ average waiting time when access network is heavy-loaded.
How to reduce network self-similarity is a hot point in current network researches. A time-slot divided algorithm is proposed to reduce the self-similarity of the aggregate traffic. When cooperating with (CAC) and scheduling algorithm, quality of service (QoS) will be guaranteed. Simulation results show that our algorithm has better performance than that of traditional carrier sense multiple access(CSMA) algorithm not only in reducing self-similarity of aggregate traffic, but in QoS guarantees.
A deterministic algorithm is proposed for System-on-Chip (SOC) test scheduling. With the optimal assignment and balance design for test wrappers, four types of incremental Sequence Pair generation methods are constructed as a cyclic iteration process. By considering the TAM width, dead space, and test area for IP cores simultaneously, the algorithm can achieve effective solutions in certain iteration steps. Experimental results on ITC’02 benchmark show that the proposed algorithm performs faster than the traditional SA method while obtaining comparable results.
A new non-orthogonal multi-carrier system is proposed. The CP-free system shows that its spectrum efficiency is better than that of the OFDM system with the same modulation. The frequency-domain maximum likelihood sequence detection based on the Ungerboeck metric is employed. In order to decrease the detection complexity, a square-root-Hanning window is adopted. The convolution constraint length among sub-carriers is only 2. The simulation results prove that the proposed system is effective and feasible in mobile channels.
Synchronization process is much complicated and essential in Ultra-Wide band (UWB) communication system for its special characteristics, extremely short transmitted pulse shape and ultra dense multi-path interference. A close-form expression of Modified Cramer-Rao bounds (MCRBs) for DS-UWB both in data-aided (DA) and non-data aided (NDA) acquisition scheme is derived. IEEE defined standard channel models are adopted in the presents of multi-access interference (MAI) during derivation. The validity of this derivation result is also confirmed by comparing this derived limit of theoretical performance and classical sliding correlation acquisition algorithm with computer simulation in fixed observation window. Meanwhile, a conclusion is obtained that the derivation under prior assumptions is a feasible tight lower bounds and the increase of multi-path delay in environment weakens the estimation performance of timing delay.
A method integrated by independent component analysis（ICA） and empirical mode decomposition （EMD） is proposed, which can eliminate the white noise from different signals. The superiority of ICA and EMD is expatiated emphatically. The basic theory and the detailed courses of construction of virtual noise channel used EMD are described. Based on time-frequency spectral characteristic of white noise, the principle of select intrinsic mode function(IMF), used the Hilbert time-frequency spectra，is proposed to reconstruct virtual noise channel. The simulations indicate that the denoising performance is effective. Compared with the denoising performance, this method is better than traditional wavelet method.
In the robot modular joint trajectory tracking control system, traditional Proportion-integral-derivative (PID) algorithm is easy to be influenced by many kinds of disturbances. By using Fuzzy adaptive method, PID parameter online auto-tuning is realized based on the Digital Signal Processor (DSP) control system. The experiment results demonstrate that the method of Fuzzy adaptive servo control scheme, compared with conventional PID algorithm, will improve system’s properties and anti-disturbance abilities. Applications in modular joint servo control systems verify the effectiveness.
Based on the inherent characteristic of the contention relationship between flows in Ad hoc networks, a notion of the link’s interference set is introduced , it extends the multipath utility maximization formulating the congestion control problem for multipath routing in Internet to that in Ad hoc networks. As the objective function is not strictly concave in the path rate, the penalty function method is applied to transform the primal problem into a new formulation to obtain the optimal solution based on the subgradient method. And the multiPath congestion control algorithm (MPCC) is also proposed. It can be implemented in a parallel fashion at each source/link. Simulation results show that MPCC can quickly quickly converge to globally optimal solutions; and, compared to the additive-increase-multiplicative-decrease (AIMD) algorithm in TCP-Reno, MPCC is more adaptive to time-varying network situations, and achieves better network performance. And thus it can be used to the practical Ad hoc networks.
To design DBL code for non orthogonal multi-carrier direct spread(DS) systems, the LS/DBL code correlation is deduced under certain condition, and the relation between frequency gap and number of codes is discussed. Meanwhile, some rules are given for DBL expanding matrix selection to reserve the zero correlation window(ZCW) property. Simulation shows that the DBL code constructed by this way will suffer no performance loss under Non Orthogonal Multi-carrier systems while the decoding complexity grows linearly with the number of subcarriers.
An improved decoding algorithm based on minimum mean square error(MMSE) for LDPC codes is proposed. The new algorithm combines processing methods of two modified UMP BP-based algorithms (normalized UMP BP-based algorithm and offset UMP BP-based algorithm) and attains the corresponding normalization factor and offset factor according to MMSE criterion. Simulation results indicate that compared with the two above-mentioned algorithms a gain of 0.03 dB can be achieved at BER of 10-6 with the proposed algorithm when a (3,6) regular LDPC code of code length 1008 and code rate 1/2 is used.
A characterization of the algebraic immune Boolean functions is presented by means of the covering vectors. A sufficient and necessary condition is given that the algebraic immunity of a Boolean function is not more than a fixed value. This result is used to describe a characterization of the algebraic immune of normal Boolean functions. It is also shown that the upper bound of the algebraic immunity of -normal Boolean functions is .
The azimuth angle and elliptic of the pulsed magnetic field sensor output light based-on Faraday effect were derived with the Jones matrix. The evolution of output light state of polarization (SOP) was described on the Poincaré Sphere method. It does illustrate what is really happening in the sensor. The output SOP effects of the linear birefringent in Faraday materials and azimuth of the polarizer were simulated, respectively. At same time, a new method of four light path measurement was proposed to eliminate disturbing linear birefringent effects on the pulsed magnetic field sensor and magnetic field output of sensor applying four light path measurement was also calculated.
In order to decrease the random access latency and to lower the collision probability, an interleave division multiple access scheme is adopted as the multiple access scheme of resource request data part of the one-step random access scheme. The number of available random identifier will be enlarged when inserting several additional bits into the data part. An asynchronous IDMA receiver is designed for multi-user detection of the data part. Analysis and simulation results show that the collision probability can be lowered dramatically by using the proposed scheme.
A multicell adaptive resource allocation (MARA) scheme was proposed for downlink Orthogonal Frequency Division Multiple Access (OFDMA) cellular system. In order to reduce the complexity of the system, the processes of subchannel allocation and power allocation was separated. The subchannel was dynamically allocated in every cell, and then the transmit power was allocated among the co-frequency users of adjacent cells based on the results of subchannel allocation. The non-cooperative game theory was employed in the multicell power allocation, and a multicell distributed power allocation algorithm was presented via pricing function. Transmit power levels of co-subchannels in the adjacent cells were coordinated, in that inter-cell interference was mitigated and radio resource utility was improved. Simulation results show that the MARA could increase throughput of the system.
A new admission control scheme was presented in packet-switched orthogonal frequency-division multiplexing (OFDM) wireless communications. In the scheme, the relationship between the packet waiting time in queue and the acceptance ratios for real-time services was derived with Markovian queueing model and Wiener prediction theory. Thereafter, the maximum acceptance ratios subject to a hard constraint on packet waiting time and handoff call dropping probability was obtained. The proposed scheme will satisfy the packet-level and call-level quality-of-service (QoS) requirements for real-time services while maintaining high bandwidth utilization. Simulation results verify the effectiveness of the proposed scheme.
The framework of a digital cinema coding/decoding system is presented. The three key technologies of this system, colorimetry transformation, image compression and packaging for distribution are studied. Then it is implemented using computer software, with some additional optimization applied to accelerate the computation speed. Experimental results show that, this system completely conforms to the DCI specification, the compression efficiency is high, and the computation speed is fast, which are sufficient for further employment in research and applications.
A practicable and secure conversation keys scheme for Ad hoc network is presented. The scheme is composed of system initialization with the help of identity-based（ID-based）and evolved passwords algorithm, nodes’ identity authenticated algorithm and conversation keys algorithm. In the nodes’ identity authenticated algorithm and the conversation keys algorithm, the ID-based passwords can reduce the computational complexity and interactive times. Additionally, the evolved passwords and random value means that the same nodes have different passwords, different keys pairs and different conversation keys during every communications. The scheme applies to the Ad hoc network also because the conversation keys don’t depend on any node. The scheme is secure against dictionary attack and types of key attacks.
For modeling multipath propagation and spatial-temporal fading correlation in frequency-selective channel, multiple input multiple output(MIMO) fading channel model is proposed. It is abstracted as a cluster-based double bounce model with multiple receiving taps. The expressions of correlation coefficient and multiple input multiple output-orthogonal frequency division multiplexing(MIMO-OFDM) channel capacity are derived respectively. The effect of spatial temporal correlation on the capacity is investigated for different physical parameters. It is shown that the channel capacity increases with the increasing total angular spread and the capacity is the function of the transmitting correlation matrix and the summation of the entire receiving taps channel matrix. Increasing delay spread taps and cluster angular spread can increase the channel capacity as well.
A multilevel congestion control (MLCC) network-on-chip routing algorithm was proposed to improve the routing efficiency. When there are medium and high level congestion, MLCC decides how to do congestion control depending on the congestion level difference of the routers. Simulation results show that MLCC maintains low latency than one level congestion control routing algorithms under uniform traffic.
Wave-guide function in multimode fiber is solved using central difference method to get the linearly polarized mode distribution and double integral is done to get the mode power distribution by laser inspirited. Two steps are the key to calculate the optical power transfer function (OPTF). At last equalization simulation is carried out and the results show that for 300-meter distance 4dB dispersion performance requirement of 10G Ethernet can be satisfied by using decision feedback equalization.
SUN Hong-yan1,2 ， ZHAO Kai1
The observation of extremely low radiation brightness temperature signal of atmospheric objectives with airborne radiometer is critical to the service of artificial rainfall and collection of meteorological data. A new airborne noise coupled digital auto-gain compensative microwave radiometer (NDMR) was designed. Using compensative technique automatically, the stability and sensitivity of such system was improved greatly. The noise signal was input into the antenna and reference source through two couplers respectively, so the instrument can detect the slight variation in the micro-wave signal in cloud within relatively wide dynamic range. The results show that NDMR was reliable for the atmospheric observation on airborne platform under the circumstance of super-cooled water. Compared to the ground-based weather radar, the instrument gained more accurate data and detected local region directly, so it enhance the detection accuracy and sampling representative.
As for the sum-product decoding algorithm of low density parity check (LDPC) codes, a difference-based decoding method is proposed. The main idea is shown as follows: the messages passed on the bipartite graph of LDPC are based on the probability differences，and the updates of both check nodes and message nodes are carried out on some special addition domain. As for the update of check nodes, only some lowest differences can be selected for reducing computational complexity. In contrast with the traditional log-likelyhood-ratio-based（LLR-based） decoding method, the proposed method has much lower complexity, while it has no obvious loss of performance and convergence.
As known, media access control (MAC) protocols for wireless sensor networks (WSNs) can exploit listen/sleep cycles to conserve energy. The relationship of the listen/sleep cycles and network performances is analyzed. An adaptive schedule medium access control (AS-MAC) for WSNs is presented. The adaptation of the cycles in MAC layer to the traffic is introduced. Simulations validate that the protocol can decrease the latency, improve the throughput and energy efficiency when traffic is dynamic.
Based on the dilemma of delay value in cyclic delay diversity (CDD), a new transmission scheme based on CDD and its channel estimation method is presented. Delay values are different among symbols with pilot. Those symbols with pilot and symbols with data are different too. With the new channel estimation algorithm, the cyclic delay diversity is robust to the delay value.
For the purpose of peer-to-peer (P2P) detection and control, a model named P2P traffic control model (PM) was presented, with the model P2P packets can be identified accurately by signature matching and the P2P traffic can be controlled by discarding P2P packets randomly. In addition, PM can detect the traffic at gigabits rate through ternary content addressable memory. With different network’s workloads, the simulations based on OPNET platform have been done and show that PM can control the P2P traffic effectively and improve the quality of service (QoS) of non-P2P applications.
Considering inter-cell interferences, service status, and channel conditions, the wireless packet scheduling algorithms are presented, in which the unsolicited grant service (UGS), real time polling service (rtPS), extended rtPS(ertPS), non real time polling service (nrtPS), and best effort (BE) services are supported. Numerical results reveal that the proposed scheduling algorithm improves the overall network throughput.
A new interpolation channel estimation method based on movement track is proposed. It puts the interpolation problem convert to seek the uniform acceleration movement track problem. Compared with the linear interpolation and quadratic interpolation channel estimation based on polynomial models, it has the characteristic of low complexity, simple arithmetic and real time computation. Simulation results prove that the performance of the new method is similar with the linear interpolation method at the lower velocity; while it is better than the linear interpolation method at the higher velocity and a little worse than the quadratic polynomial interpolation.
An image color quantization algorithm base on peer group filtering (PGF) and vector quantization (VQ) is proposed. Firstly, PGF technology is used to filter image in LUV space, which smoothes image and maintains edges and details. And then, the local maximum of the 3D color histogram of the filtered image are chosen as the VQ codewords to make the image quantized. A quantization distortion function is defined, it takes visual characteristics into account. Split of cluster with the highest quantization distortion is iteratively performed until the requirement of total distortion is satisfied. Finally, agglomerative clustering can be applied to merge close clusters if further reduction of number of quantization colors is desired. The experiment shows that the objective and subjective quality of image produced by our algorithm were obviously better than that classical K-means algorithm.