- EI核心期刊
The problem discussed here is the research work of linkage mechanisms, which has relations with geometry. These works include planar and spatial mechanisms, series and parallel mechanisms, geometrical modeling of the mechanisms and equations solving. The kinematic analysis and synthesis of mechanisms are also discussed. Except traditional method, modern ones for solving these problems are outlined here. When computer is used, some special problems appear in the calculation and are also discussed.
A network coding based transmission scheme is proposed for multiantennas based uplink wireless relay networks. Its performance is evaluated from the perspective of ergodic capacity and outage probability, and compared with ordinary relay diversity scheme and with orthogonal space time coding scheme. Calculations show that network coding can effectively improve the performance of multiantennas based uplink wireless relay network, and the more the antennas, the better the performance.
A novel data dissemination scheme——matchmaking by geometric structure quorum （MMGSQ) in wireless sensor network is proposed. The MMGSQ incorporates a new quorum named spatial neighbor proxy quorum which utilizes the geometric properties of the planar graph to reduce the quorum size. The MMGSQ improves energy consumption by reducing message transmissions and collisions, increases the matchmaking success rate and is easy to be implemented. Theoretical analyses and experimental results indicate that the new data dissemination algorithm with related quorum system has higher scalability, energy efficiency and matchmaking success rate than those of the original means. It is especially suitable for data dissemination in largescale wireless sensor networks.
With thinking of soft symbol interference cancellation, a Gaussian approximation method and minimum mean square error (MMSE) method are proposed to obtain the soft information of each bit. According to the transmission property of Golden code, the methods are deduced to compute the soft information in the system. Analysis indicates that, compared with the traditional list sphere decodemaxinum a posteriori(LSDMAP) method, the Gaussian approximation method and the MMSE method have lower complexity. Simulations show that the iterative detection performance of proposed methods is close to the LSDMAP method, which achieve a fast iterative detection of Golden code.
A new depth estimation algorithm based on graph cuts is proposed to improve the accuracy of depth maps. Average luminancegradient matching method is proposed to replace unitary pixel luminance matching. The graph structure is changed considering depth correlations between each adjacent pixel. The depth of the colocated pixel in previous frame is used to restrict the depth of current pixel. Taking consideration of the spatial and temporal features of depth maps, the accuracy of estimated depth maps is then improved. Experimentss demonstrate that the proposed method can generate more accurate depth maps than the traditional graph cuts in algorithms.
In order to enhance the diagnosis efficiency with the accumulated network sample, and because the standard support vector machine doesnt support incremental learning directly, a boundary deflection overlay incremental support vector machine is proposed. According to the movement of separating hyperplane caused by the newly added training samples that violate KarushKuhnTucker conditions, the boundary deflection overlay algorithm is also designed to preextracts support vector reproducing region as the work set for incremental training, which solves the problem that nonsupport vectors transform to new support vectors. Analysis and simulation show that the method can not only reduce the work set effectively, but improve the training efficiency greatly without affecting the diagnosis accuracy.
The selfsimilarity of peertopeer (P2P) traffic is studied based on fractal method. Different from former researches, the traffic of single protocol is concerned. Two popular P2P applications are tested and showen that the application layer traffic tends to be selfsimilar. The selfsimilarity is more stable under behavior scale than under time scale. The selfsimilarity of the P2P traffic is applied to P2P traffic identification. A new traffic identification algorithm is proposed based on the fractal dimension and positivity of the network traffic. Experimentss show that the performance of the proposed algorithm is better than the existed in terms of accuracy especially for encrypted traffic.
Different transmission strategies for decode-and-forward parallel relay networks based on superposition coding are investigated. In particular, an optimal-cooperation (OC) strategy is proposed to minimize the aggregate power consumption for a target transmission rate, which requires strict synchronization at the destination node to achieve its optimal performance. A non-information-overlapping (NIO) strategy is then proposed to avoid the synchronization problem. Compared with OC strategy, NIO strategy is more suitable for actual relay networks. Furthermore, a reduce-relay-selection method involving only 2-level superposition coding is given to trade off between complexity and performance. Analysis shows that the performance gap between NIO strategy and OC strategy is negligible. the best two relay nodes are selected in adequating to achieve most performance gain of NIO strategy even if the number of relay nodes is large.
High speed data stream brings the phenomenon that the data rate is higher relative to the ensemble classifiers computational power, so the ensemble classifiers cant train all data which reached recently to update themselves. An ensemble classifiers is proposed based on biased sample. Expectation error is analyzed through biased variance decomposition method, and the data is also biased sampled by computing all datas expectation error contribution degree which is waited for being sampled. This method can reduce time to train and update ensemble classifiers and will be contrasted with random sample ensemble classifiers. It indicates that this method has more prediction accuracy on condition the same proportion of sample.
In order to meet requirements of spacecraft tracking, telemetry and command (TT&C) transponder in direct sequence spread spectrum system, the code tracking loop is investigated. A new code tracking loop is presented which adopts a new kind of dot product power discriminator and a new pseudocode generator in which the phase can be accurately adjusted. Moreover, the related distance and bandwidth of code tracking loop will adaptively switch to solve the contradictions between locked timers, convergence range and tracking accuracy. Furthermore, a new implementation method of code tracking loop is proposed in which discriminator and loop filter are timesharing same arithmetic unit. Simulations and measurements are given.
A crosslayer design and path quality based adaptive scheme for mobile Ad hoc network accessing Internet is proposed. The proposed scheme adopts an integrated metric taking into account the combination of residual bandwidth, packet delivery ratio and node load to meet the needs of quality of service requirement of multimedia traffic transmissions. Furthermore, an adaptive algorithm is proposed to provide the best coverage of gateway advertisement according to dynamically adjusting broadcast range and sending interval of gateway advertisement messages in terms of gateway load and network topology. Simulations show that the proposed algorithm can effectively improve Internet connectivity performance with reasonable control overhead.
Overlay network topology and search algorithms have important influence on resource query efficiency. A file resource grid system called ring petersen (k) cluster grid (RP(k)Cgrid) is designed, it is a hybrid topology overlay network composed of two parts: ring petersen (k) graph (RP(k)) and resource cluster. Message routing algorithms are discussed in detail. Cluster head probe, cluster head flooding and ring petersen (k) cluster (RP(k)C) scan mechanism are executed on RP(k)Cgrid. Replica is created at cluster head node for successful crosscluster query. Query register mechanism efficiently voids flooding within cluster. Experimental result shows that the RP(k)Cgrid has good efficiency in scalability, search delay and load balance.
In order to improve the utilities of the multichannel wireless multihop networks, a practical crosslayer optimization mechanism is proposed. With the proposed mechanism, each node can use joint design algorithm to adjust flow rates distributedly in transport layer, and can use the proposed distributed scheduling algorithm to allocate rates for links in link layer. The gateway uses the proposed minimal interference cost based channel allocation algorithm to allocate channels centralizedly. Through transmitting informations among layers and nodes, the proposed mechanism can coordinate the operations of these layers, so the complexity is decreased, and the signaling overhead is reduced compared with the centralized algorithm. Simulations show that the proposed mechanism can achieve fast convergence, and ensure fairness among flows. With the increasing number of available radios and channels, the rates of flows and network utilities increase.
In order to optimize media traffic through push to talk over cellular (PoC)4 i nterface in Internet protocol (IP) multimedia subsystem, an improved optimizati on mechanism is presented by taking loosecoupling and distributedcontrolling ideas into consideration. Under the new mechanism, the media traffic through Po C4 interface can be reduced greatly, and the network bandwidth can be saved mu ch and waiting delay of realtime transport protocol packages in PoC serv er can also be shortened obviously. Analysis and simulation show that the new me chanism performs more effectively than do the original transmitting mechanism an d the media traffic optimization mechanism proposed by open mobile alliance.
The unicasting relay protocols in multiinputmultioutput multirelay syste ms are analyzed. The expression of the received signaltonoise ratio with uni casting relay protocols is derived, which is a function of some singular values and angles between singular vectors related to backward and forward channels. Ba sed on the maximizing capacity criterion, the relay selection strategies with in stantaneous and average channel state information are presented with simplifying the capacity expression. With average channel state information it is a trade off scheme between the feedback overhead and the ergodic capacity performance.
A multichannel adaptive media access control (MAC) protocol based on the conce pts of competing control channel (CCC) and reserving control channel (RCC) is pr esented. In order to access wireless channels, cognitive users reserve the sub frame of RCC through CCC that obligates the access opportunities for different t raffic. The users apply the required bandwidth using RCC based data channel. The channel is distributed and recycled by updating a channel state table. Simulati ons show that the proposed protocol can effectively schedule the accessing of us ers and exhibit good scalability. It significantly reduces the probability of co llision and congestion, thereby improves the endtoend delay and network thro ughput.
The distance vector routing protocol can not deal with network failures effectiv ely, causing significant forwarding discontinuity after a failure. The drawback with this protocol is that it needs to trade off routing stability and forwardin g continuity. To improve failure resiliency without jeopardizing routing stabili ty, a fast network selfhealing mechanism is proposed for distance vector routi ng protocol. The new mechanism includes a backup multinext hop for fast local rerouting strategy and a network stabilitybased triggered routing update mecha nism. Analysis and simulation show that it can deal with the simultaneous failur es of multiple arbitrary links effectively, and can efficiently improve stabilit y and availability of networks.
In order to solve the problem of the low throughput of the dropfront (DF) and dropoldest (DO) in delay tolerant networks (DTN), an enhanced congestion contr ol strategy is proposed under conventional epidemic routing, that is called drop copy rate (DCR). When the congestion of node happening, the copy rates of packe ts stored in buffer and arrived at this node at the same time are calculated, ac cording to the copy numbers , the lapse time and the packet that has the highest copy rate will be deleted, and then the congestion can be relieved. Simulations indicate that DCR decreases the packet loss ratio, and improves the throughput, and relieves congestion effectively of the networks compared to DF and DO.
A new cooperative spectrum sensing scheme is proposed to reduce the cooperation overhead. After comparing the local observation with the threshold, the user cou ld decide, whether or not, to transmit local decision to the base station. Two f usion rules, counting rule and NeymanPearson rule, are investigated for the pr oposed sensing scheme. Analysis and simulation show that the proposed scheme gua rantees sensing reliability without any performance loss and reduces the communi cation overhead significantly to achieve high energy efficiency in sensing cooperation.
Regarding to the multicluster Laplacian power azimuth spectrum (PAS)，a closed form expression for the channel correlation applicable to the uniform linear a rray (ULA) and uniform circular array (UCA) is derived. Both the PAS and cross polarization discrimination (XPD) are taken into consideration. The channel corr elation values introduced by the singleand multicluster Laplacian distributi on with the same angular spread(AS) are compared. The channel correlation as a f unction of the antenna spacing of the ULA or the radius of the UCA is analyzed i n conditions of different ASs in cluster. With different mean angles and ASs the equivalent antenna spacings which produce the same channel correlation with cor responding XPDs are also presented.
A low complexity iterative precoding algorithm is proposed for multiuser multipl einput multipleoutput (MIMO) downlink systems where a single data stream is allocated to each user. In the algorithm, precoders are designed according to th e zero forcing (ZF) criterion, and receive filters are updated via maximum ratio combining. Assuming one data stream per user, the algorithm has almost no perfo rmance loss compared with the iterative NuSVD algorithm, and the magnitude of co mplexity per iteration is one Kth that of the published one (K denotes t he number of users, K≥2), thus saving more than 50% total complexity costs. Simulations verify the effectiveness of the proposed algorithm.
Because of interference between both the relays and the destination, the two opportunistic relaying protocols are proposed to minimize the outage probability according to whether the direct transmission is considered or not. Moreover, if the direct transmission is taken into account, maximal ratio combining is deployed at the destination to combine the direct transmission and relay transmission. The outage probabilities of the protocols are derived over the independent nonidentically distributed Rayleigh fading channels. Simulations validate our analysis. Furthermore, in terms of outage probability, opportunistic relaying considering the interference is better than that without considering the interference, and opportunistic relaying with a direct link outperforms that without a direct link.
An adaptive interleaving scheme for orthogonal frequency division multiplexing system is proposed. Based on the channel state information, whatever, an interleaver from a pool of candidate interleavers is selected. As the selected one is expected to have larger minimum Euclidean distance at receiver, the scheme can significantly improve the decoding error rate performance. Compared with the adaptive interleaving schemes proposed in literatures, the proposed has no interleaving pattern synchronization problem and requires only a few bits for the signaling.
Cooperative sensing can effectively improve the performance in cognitive systems, and the main benefit comes from some high reliable users but not all users. The performance of the optimal fusion rule is analyzed under the system model of IEEE 802.22. Based on the analysis, a new user rejection algorithm is proposed to reduce feedback resource greatly with limited performance loss. The proposed sets a threshold to reject users with low reliability. Analysis and simulation show that the user rejection can effectively control the system performance loss by setting a reasonable threshold. Moreover, it also reduces the requirements of feedback channel resources and provides a foundation for further cooperation sensing system optimization.
Transformed matrix based nonnegative matrix factorization method is proposed. It shows that the new method, with similar complexity to the known schemes, is efficient in reducing the iteration number for nonnegative matrix factorization.
Aiming at the problem of link layer handover requires more signaling interaction, which increases the signal cost and handle delay when fast mobile IPv6 is used to wireless IEEE80216based relay networks, a fast handover scheme is proposed to apply fast mobile IPv6 to IEEE80216j networks, that determines the crosssubnet handover in advance through the interaction of link layer messages, so as to reduce the handover signal cost and speed up the handover. Simulations show that the handover signal cost and handover delay are decreased in proposed scheme.
The power allocation strategy based on the game theory for the cognitive radio system is studied. The best utility function for the gametheoretic strategy is analyzed. A distributed power allocation strategy is proposed, where the limit power for each cognitive user is based on its proportional interference to the primary user and satisfying the constraint of the total power interference to the primary user. The comparent performances of the different proportional schemes are investigated. Simulations show that the best power limit for each cognitive user is to produce the same interference to the primary user.
A short signcryption scheme with ciphertext anonymity and forward security is proposed, which can protect the privacy of the sender and the receiver identities. The security models, including semantic security, unforgeability, ciphertext anonymity, forward security and verifiability, are analyzed in the random oracle models. In computational cost, the proposed scheme only need two scalar multiple operators in signcryption phase and two bilinear pairings and one scalar multiple operators in unsigncryption phase. Compared with the short signcryption schemes up to date, the computational costs of the new scheme are lower than those of signcryption schemes available where it has stronger security components, which can be used in the security requirement such as bandwidth constraint and identity hiding.
Based on hierarchy noncooperative game theory in open sharing model, a distributed algorithm used for adaptive power control is proposed. The algorithm is composed of outer updating and inner updating, in which each user can implement periodic information interaction and adjust its transmitted power adaptively. Through Simulation verifies that the information interaction can be decreased with the proposed when distributed updating, the nearoptimal solution is obtained at the same time.
To analyze the impact of quantized feedback on multi-antenna relay system, the letter derives the outage probability and capacity of relay system,which retransmits signal by using limited feedback beamforming. First, we derive the moment generation function of received signal-to-noise ratio and achieve the outage probability by using inverse Laplace transform. Second, we derive the capacity upper bound based on Jensen's inequality. Finally, Numerial results are given to verify feedvack beamforming could achieve the tradeoff between and feedbacks. The system performance can be improved by the increase of antenna numbers and feedback bits.