- EI核心期刊
Its necessary to have deep understanding on the ubiquitous networks, including the origin, concepts and characteristics of ubiquitous computings. The relations between ubiquitous networks, sensor networks and internet of things are analyzed. A layered architecture and information plane model of ubiquitous networks is presented. Suggestions on key technologies and challenges the ubiquitous networks has to meet are proposed.
Effects on the slow light properties of the photonic crystal linedefect waveguide are researched for designing photonic crystal structure with excellent slow light properties. Through changing the position and the size of the defected rods, the frequency and group velocity of the guided mode and the group velocity dispersion are analyzed with planewave expansion (PWE) method. Analysis indicates that the group velocity of the slow light is mainly affected by the radii and dielectric constant of the defected rods, and the group velocity dispersion is decided by the change of the defected rods’ location. The photonic crystal structures with excellent slow light properties can be achieved through designing the waveguide based on the conclusion.
The existing representative timing recovery schemes is analyzed. And according to their problems of high requirement of sample rate and nonalldigital implementation a new alldigital timing recovery scheme is presented for highspeed optical coherent receiver which combines Gardner timingerror detector and interpolator. The new scheme has a series of advantages, such as low complexity and alldigital realization, etc. Also, the good performance of the new scheme is demonstrated in a 112Gbit/s polarization multiplexed nonreturntozero differential quadrature phaseshift keying (PMNRZDQPSK) transmission system.
The current gossipbased protocols follow a pure random selection process, easily resulting in long convergence time and large volume of nonInternet service provider (ISP)friendly traffic. A communityaware gossip protocol is proposed. By clustering peers into communities, peers can know their positions in the network in terms of vicinities to the communities. The presented scheme can increase the efficiency in neighbor selection and reduce the nonISPfriendly traffic across ISPs. Analysis and simulation show that the proposed gossip protocol can improve the utility of physical network usage, and stimulate the overall performance as well as appeal to more participating peertopeer (P2P) users.
To study the characteristics of traffic behavior in wireless mobile networks, a continuoustime semiMarkov process model (CTSMM) is proposed. Based on the large amount of traffics gathered from real wireless networks in China, the characteristics of traffic behavior are analyzed deeply. Specifically, the session arrival, the session duration and the session traffic size for single cell and multiple cells environments are studied. CTSMM is proposed to characterize traffic behavior. Meanwhile, based on the collected traffic data, the proposed model is verified for reflecting the properties of the traffic behavior in wireless networks. Using this model, the wireless network design, the resource management optimization, and the dynamic wireless spectrum utilization, are well performed.
The traditional shortest path algorithm is not suitable for the routing choice in delay tolerant networks (DTN). According to the routing features in DTN，a new shortest path algorithm hopbased, timevarying cost (HTC) is proposed based on the hop and the cost varied with the time. The design of the routing algorithm not only considers the space factor between the nodes in DTN, but also the time factor of the wireless links and the complexity and accuracy. Simulation compared with the existing routing algorithm such as first contact (FC), minimum expected delay (MED), indicate that the algorithm proposed by this paper is more effective to get the shortest path.
To restrain the pulse broadening in the communication system, a new type of dualconcentriccore photonic crystal fiber (DCCPCF) composed of single silica material is put forward based on the theory of dispersion compensation. The dispersion value of fundamental mode can achieve up to -6000ps/(nm〖DK〗•km) at 155μm. Analysis indicates that the inner core fundamental and outer core defect mode with phasematching wavelength (λp) as a critical state will propagate forward alternatively between the inner and outer core region, and the effective indices intensely appears fluctuations due to modes coupling at phasematching wavelength. By analyzing the perturbation of dispersion with two structure parameters d1, d2 changing, the instruction for actual fabrication at a certain extent is provided.
A limited Chinese grammar acquisition system (LCGAS) based on part of speech division is built for service composition to solve the halfautomatic generation of ontology instance in the technology of service composition. At the same time, in order to express the acquisition result of the acquisition system consistently with the ontology, a description logic denotation method of limited Chinese grammar is put forward. At the end of the paper, the result of performance test showed that the LCGAS had a higher success ratio and when combined with the denotation method, it could better solve the problem of half automatic generation of ontology instance.
A spectrum sharing scheme is proposed that allows the cognitive users to select either direct transmission or cooperative underlay transmission adaptively according to the spectrum detection in cognitive relay networks. Moreover, analysis on the cognitive network with this scheme is presented. Based on signaltointerference and noise ratio (SINR), the closedform expressions of outage probability and the symbol error probability are derived. Simulation shows that this scheme can achieve better performance than the traditional overlay scheme and underlay scheme in guaranteeing the primary link and enhancing the performance of the cognitive network.
A new method of array geometry arrangement based on ring array for wideband reconnaissance receiver is proposed. With the aid of aliased spatial information from two independent sampling channels, solving ambiguity algorithm and pair method, it can provide unambiguous direction of arrival (DOA) estimation. The simulation result indicates that azimuth angle and elevation angle are estimated in high performance and paired correctly under the circumstance of small search load. Data obtained from two channels can be processed separately. Realtime performance of algorithm is improved.
A selection scheme is proposed for the cooperative transmission of multipleinput multipleoutput (MIMO) regenerative cooperative system. Single relay node is selected to maximize the minimumcase channel power gain among all relay nodes. Outage performance is analyzed through an approximate method. Under this selection scheme, a simple power allocation method is also developed for the sum power constrained network. Analysis and simulation demonstrate that this scheme can achieve a significant improvement in terms of outage performance. A distributed selection scheme is proven to have a good balance between the system performance and the implementation complexity. Therefore, it is a promising choice for practical utilization.
Aiming at decreasing of binding update cost and data transfer cost of proxy mobile Internet protocol version 6 (PMIPv6) network, the concept of integrated optimization is adopted. Comparing the cost of PMIPv6 with MIPv6, the decision function used to determine when PMIPv6 is adopted preferably is obtained, and the adaptive mobility management scheme is proposed, that allows a mobile node (MN) residing in a PMIPv6 domain to select a suitable mobility management dynamically from PMIPv6 and MIPv6 according to its working parameters. Simulation shows that the proposed scheme will have good utilization of resources.
To stimulate the cooperation between the nodes in selfish networks and to make joint assignment of bandwidth and route, the auction theory is used to analyze the rational behavior of the node in selfish networks and to make the bandwidth assignment for multipath multihop routing as the auction model. Two schemes of bandwidth assignment for the multipath multihop routing are proposed. One scheme is based on convex optimization, the other is based on least cost path (LCP). Analysis illustrates that the mechanism is strategyproof. Extensive evaluations show that the mechanism can simulate the cooperation between the players.
In order to authenticate the binary images, a fragile watermarking technique for image authentication and ownership verification is proposed. The pixels are firstly divided into two groups according to pixel spread difference (PSD), one is the “flippable” pixels and the other is the “unflippable” pixels. Then, the image block is permutated by a chaotic sequence. According to the encrypted ownership watermarks, the “flippable” pixels in the four parts of the image block are altered to get the watermarked image block. Experiments show the imperceptibility of the watermarking process, the proposed algorithm can successfully localize the content modifications, and protect the uniform regions that is the key problem in binary image authentication. The photonic crystal structures with excellent slow light properties can be achieved through designing the waveguide based on the conclusion.
By translating the cooperation game model between participants in the data services market into a bargaining game model, using Edgeworth box and bargain theoretical model, this paper analyses the bargaining mechanism and the balance results of bargaining between operators and service provider (SP) about network construction and cooperation. In addition, an optimized model and its sensitivity analysis is discussed. The research shows that SPs have a collective advantage in the bargaining game, while operators can improve their bargaining power by participating in the data services market. Therefore, there exists a balance in the bargaining game between operators and SP.
In order to dynamically analyze the endtoend distortion, a new joint sourcechannel ratedistortion (RD) model for wireless lowbitrate video transmission is proposed. The source and the channel distortions of I and P frames are respectively analyzed on a group of picture (GOP)，and the propagation of distortion within the GOP is discussed. It can dynamically estimate the average endtoend distortion of each frame in the GOP according to packet loss rate and characteristics of the video sequence. Experiments show that the accuracy of this model is satisfactory.
For analysis and description of the electromagnetic field in a periodically diskloaded circular waveguide, a modematching technique is introduced and the electromagnetic field is expressed according to the waveguide modes. The particular way is that a specific diskloaded diaphragm is considered in the waveguide and the reflection problem arising from one incident is solved using the modematching technique. Thereafter, a matrix eigenvalue equation is derived for the periodically loaded waveguide. Solution of this equation yields the dispersion curve for the field structure. Experiment shows that each mode matches the boundary conditions and the matching technique used to analyze the electromagnetic field distribution in periodic linear travellingwave.
Spatial channel pairing and mapping at the relay node are proposed to be used in the zeroforcing (ZF) relaying system to mitigate the relaying noise. A spatial channel pairing (mapping) matrix is presented between the backward filter and the forward filter at the relay node. The spatial channel pairing based on permutation matrices is used when several destination nodes with singleantenna are supported by the relay node, while the spatial channel mapping based on unitary matrices is used if a destination node with multiple antennas is supported. Analysis and simulation demonstrate that the noise power in the relaying signal decreases with the spatial channel pairing (mapping) and the received signaltonoise ratio (SNR) of each data stream is improved.
A New method for constructing set of zero correlation zone (ZCZ) sequence pairs and ZCZ sequence pairs with large family size is proposed. It can be used in approximatelysynchronized codedivision multipleaccess (ASCDMA) system for the reduction or elimination of the multipath interference and multiple access interference (MAI) of the system. The capacity of increasing users is large with satisfactory. First, almost optimal ZCZ sequence pairs set can be generated from the correlation product of unitary matrix and perfect sequence pairs with difference shift operation. Second, a new method for constructing ZCZ sequence pairs set with larger family size and longer zero correlation zone from a known one is presented, it can be generated from the correlation product of unitary matrix and original ZCZ sequence pairs set with difference shift operation. These methods are applied to binary, ternary quadricphase and multiphase case. Performances of ZCZ sequence pairs set constructed by the proposed methods are so good that they can satisfy requirements of ASCDMA system within the range of allowed time delay chips.
To provide efficient topology aware service, the transmission loss effects and the metric space property of peer distances in peer to peer (P2P) overlay network are discussed, the P2P clustering service is proposed as well. The service solution manages P2P client peers and maintains clustering view (CV) with clustering initiation and optimization interfaces and algorithms, and supports crossapplication topologyaware with CV querying interfaces and the CV mapping algorithm. Simulation indicates that the solution provides more accurate recommendations of closest neighbors than traditional methods based on coordinate space.
In order to further expand the application field of GTEM cell, a method of testing a total radiation power (TRP) in GTEM cell is proposed according to the characteristics of GTEM cell. The equivalent electric dipole moment (EDM) and magnetic dipole moment (MDM) are inverted through the testing in GTEM cell, the results by |S11| parameter are compensated, and the EUT’s TRP testing results are calculated. Experiments show that this method for new TRP testing and its compensation are simple and accurate, it has a practical value in wireless devices testing in some major social activities and small antenna’s performance testing.
To eliminate cochannel interference, multiple antennas are generally used at receiver to provide spatial multiplexing. Because the traditional methods for receiver need precise channel state information (CSI), a new interference cancellation method based on independent component analysis (ICA) is proposed. The desired signal is extracted according to the received signals and a few known information of communication protocol, hence the CSI is not necessary. Simulations show that the proposed method is approximate to the best linear receiver in terms of signaltointerferenceandnoiseratio (SINR), the difference is less than 01dB.
In the conventional gradient algorithm, the convergence points are difficult to be found, an intensive analysis on the gradient adaptive online independent component (ICA) methods is presented. It indicates that the digital image is a magnitude bounded signal, the convergence point in the conventional gradient algorithm will be imposed on the learning process, making the gradient descent processing convert rise processing. It ensures that when the ending codes get to the receiver, the separation matrix can be storage at the optimal point of separation. Simulation shows that this new method is with stable performance and numerical stability, and is an efficient independent component analysis algorithm.
In cognitive radio (CR) networks with slotted channels, a brandnew definition，channel availability vector (CAV), which characterizes the state information of a group of channels, is proposed based on spectralcorrelation prediction in order that the secondary users can find the available channel as rapidly as possible. The problem of sensing time minimization is formulated as a Markov decision process (MDP), and the best sensing strategy for current CAV is figured out. Through real measurement data for spectrum availability that are acquired from Guangdong province, it is verified that, as a satisfactory solution for lowrate services in highcongested spectrum, the predictionbased scheme outperforms the random one and the sequential one to minimize sensing time for secondary users.
In order to realize the transparent bit rate and the tunable frequency of frequency shift keying (FSK) in the optical label switching (OLS) system, a new method is proposed and verified by simulation with 125Gbit/s FSK label which is generated by polarization modulation and 20Gbit/s amplitude shift keying (ASK) payload. The bit error rate (BER) performance of combined orthogonal FSK/ASK signal is also researched by simulation in the case of backtoback and the fiber transmission. Besides, the extinction ratio (ER) of ASK payload and the frequency spacing of FSK label have also been studied to obtain the better performance of this OLS system. It is indicated that larger frequency spacing of FSK label will deteriorate the ASK payload, but has little influence on FSK label; larger ER of ASK payload can improve the ASK payload, however, it will bring adverse impact on FSK label. As a result, the optimum ER of ASK payload and the most proper frequency spacing of FSK label are selected to be 4dB and 50GHz, respectively.
Compared with the classic frequent pattern mining (FPM) algorithms, the dynamic FPM algorithms on fast and massive data streams have become top research nowadays. A new batch mining algorithm in data streams called stream frequent closed labeled tree miner (SFCLTreeMiner) is proposed. SFCLTreeMiner uses a kind of addingremoving method between closed tree sets. Also it provides a time decay module for reasonable data updating. Experiment shows that SFCLTreeMiner is efficient in data streams mining by reducing consuming dramatically.
A rate control algorithm for adaptive prediction error and quantization matrix is proposed in order to improve the performance of rate control in H.264 further. Firstly, the new algorithm determines whether discrete cosine transform (DCT) is applied to the macroblock according to the gradient directional weight of macroblock and to the simplified rate distortion model. Secondly, the quantization parameter (QP) is calculated through a new dual target bits allocation model, and then the slope coefficient is calculated by the weighted average of slope in the macroblock. Finally, the macroblock is quantized by the quantization matrix determined according to QP and slope coefficient. Simulation shows that, compared with rate control algorithm of basicunit in H.264, the proposed algorithm restricts coding time dramatically and controls bitrate precisely. Moreover, the peak signal noise ratio (PSNR) is increased with 021dB in the proposed algorithm.
For the problem on a twouser Gaussian interference channel, Gaussian interference channel with a common relay is considered based on cooperation communication technology. Two system models of Gaussian interference channel with a common relay are proposed. For each of two system models, upper and lower bounds on achievable sum rate are studied. Performances corresponding to different relay locations are compared and proved by simulation results. The performance of two system models proposed here outperforms the communication system without relay.
To improve utilization of the television (TV) bands, a hierarchical spectrum trading model is presented to analyze the interaction among TV broadcasters, wireless regional area network (WRAN) service providers, and WRAN users. In this model a double auction is established among multiple TV broadcasters and WRAN service providers. In particular, the theory of evolutionary games is used to investigate the dynamics of WRAN user behavior and solution in network selection. A centralized algorithm is proposed to implement the proposed evolutionary game model for network selection. Then, multiple WRAN service providers compete with each other by adjusting the service price charged to WRAN users. To model the competition, a noncooperative game is formulated. In order to maximize their own profits, every WRAN service provider should seek the optimal spectrum bidding and service pricing strategies. Numerical results are presented on the performance of the spectrum trading model. The proposed framework will improve spectrum utility efficiency, and provide large economic and societal benefits.
For determining the polarity of sentiment words, an algorithm based on PageRank technology is proposed. A graph constructed whose nodes consist of unlabeled sentiment words and a few sentiment seeds, and the weights between each two nodes based on the semantic similarity of HowNet are also gained. With the PageRank technology on those seeds the polarity of the unlabeled sentiment words can be obtained. Compared with the methods based on HowNet to judging polarity of sentiment words, the proposed algorithm of combining PageRank technology shows its effectiveness by 10% increase of the precision.