- EI核心期刊
The faults localization method using active probing is investigated in this pape
r in the context of vector span. A probe station deployment approach is proposed to support the localization of multiple faults. The faults in the network can be localized sooner and costeffectively using the active probes sent from the probe stations placed in the network. We provide experiments to show that the proposed approach can minimize the number of probe stations and localize the multiple faults in the network.
For heterogeneous networks, a method of multiradio transmission diversity is proposed in order to exploit the multiradio access diversity gain. The packet level forward error correction (FEC) is integrated with multiradio transmission at sender. In order to exploit the considerable multiradio transmission diversity (MRTD) gain and provide the efficiency of system throughput, the coded packet is adaptively allocated to each available radio access according to minimizing the probability of irrecoverable loss at receiver. The analysis and simulation on its performance are proven that the proposed scheme has optimal transmission reliability and efficiency especially in the terrible channel condition.
In order to extract the Chinese frequent strings (CFS) accurately and make better use in language models, a new method for CFS extraction using string segmentation degree is proposed. Unigram and bigram language models based on this CFS extraction method are built. Experiment shows that the CFS based language model can deal with the lack of long distance dependency problem in character and word based language model. It also shows that the CFS based language model has lower model perplexity and higher pinyintocharacter conversion correctness compared with the model based on previous CFS extraction method.
A mode adaptive opportunistic transmission scheme in multiuser multi-input multioutput（MU-MIMO） downlink with limited feedback is introduced. In each time slot only eligible mobile station (MS) whose channel quality exce eds a preset threshold would select transmission mode, including eamforming (BF) and spatial multiplexing (SM) and adaptively feed channel information. With feedback information, base station (BS) schedules one user out of candidate MS. Analysis is employed in evaluating the proposed scheme. Monte-Carlo simulation shows that the scheme can achieve high capacity as well as low outage probability with limited feedback cost.
A prediction algorithm based channel borrowing scheme on heterogeneous wireless network model composed of IEEE802.11 wireless local area network（WLAN） and time division-synchronous code division multiple access（TD-SCDMA）is proposed to solve the problem of spectrum shortage. The scheme refers to current horizontal channel borrowing strategy and proposes a channel reserved mechanism with channel borrowing prediction algorithm. Performance simulation shows that this scheme can efficiently decrease blocking probability and improve system performance.
In case of failed location update, a significant consequence is the incapability when establishing the valid route for the potential call connection; it will seriously degrade the network performance. A quantitative analysis of the location update failure effect on the call blocking probability in the wireless network is performed. For the sake of general applicability, the call blocking probability is formulated with the call interarrival time is exponentially distribution and the location area residence time is generally distribution. It is shown that the next call blocking probability is related to location update failure probability, call to mobility ratio and the previous call status. Numerical examples are presented to show the interaction between the call blocking probability and location update failure probability. Discussions on the sensitivity of teleparameters are also given.
The decentralized estimation of a noise-corrupted deterministic parameter in wireless sensor networks with the aid of relay is considered. A new relayaided decentralized estimation (RADE) scheme is proposed, by which relay collects the overheard messages from sensors and sends the locally processed message to a destination. Amplify-and-forward (AF) and estimate-and-forward (EF) strategies are proposed and the corresponding closed-form solutions are derived. Numerical simulation shows the proposed strategies can provide better estimation performance without any bandwidth loss.
Introducing the spatial distribution information of alternating current (AC) coefficients into the feature extraction,a new Joint Photographic Experts Group (JPEG) image retrieval is proposed. Firstly，according to the characters of AC coefficients, invariant for the rotation, AC coefficient distribution entropy is presented. Meantime, because of the different effect of each AC coefficient on the retrieval precision, the weight function for the entropy is proposed; thus can avoid the mistaken retrieval and losing retrieval. Not only statistical distribution but also the spatial distribution of discrete cosine transform (DCT) coefficients are taken into account, it is robust for transform, rotation and scale. Experiments show that the new method has a better performance both in retrieval efficiency and effectiveness.
Prosodic structure prediction is an important component in mandarin text-to-speech (TTS) system. A prosodic structure prediction method is proposed, based on the conditional random field (CRF) algorithm. Prosodic word model and prosodic phrase model utilize CRF method for machine learning based on automatically segmented and tagged features and hierarchal prosodic structure information extracted from a large-scale manually labeled speech corpus. The approach achieves F-score of 90.67% in prosody word prediction and 80.05% in prosody phrase prediction, 3.62% and 5.65% higher than that of max entropy (ME) algorithm based method. Experiment results show that the approach of CRF based method makes considerable improvement in prosodic structure prediction, and works well in real mandarin TTS system.
On the study of several commonly used algorithms, a new weighted fusion of multi-mode blind algorithm is proposed: when the output signal of the equalizer is reliable, MMA-assisted modulus algorithm (MAMA) is used, otherwise modified constant modulus algorithm (MCMA), multimodulus algorithm (MMA) and MAMA are weighted and merged together. On the other hand, by controlling the weight of each algorithm and making it in direct proportion to the iteration number, the performance is evidently improves. Simulation proves that the new algorithm is stable, and could reach inter symbol interference (ISI) of -35?dB after about 2?800 iterations in the underwater environment.
LIAO Xin1,KONG Luting1,JIANG Jun2,ZHANG Ping1
The effect of channel estimation error on the performance of multiuser multiinput multi-output (MIMO) systems with zeroforcing beamforming (ZFBF) in uncorrelated Rayleigh flat fading channels is investigated. An adaptive resource allocation algorithm with the total transmit power constrained and to satisfy the target bit error rate (BER) is proposed to maximize the system effective throughput. The active users are determined by users' channel state information and fairness. To obtain closed form solution for power and rate allocation, the algorithm uses the asymptotic Gaussian convergence characteristics of the packet outage probability. Numerical analysis shows that the system effective throughput is improved, benefited from the consideration of channel estimation error and the guarantee of users' quality of service (QoS) and fairness, while the computational complexity appears low.
To obtain optimized inverse kinematics solution for a class of redundant mobile manipulator (MM) quickly and accurately, an inverse kinematics method based on genetic trust region algorithm combined with analytical solution is proposed. Manipulator's inverse kinematics expressions expressed by mobile vehicle's movement parameters are derived. The flexibility principle to determine the objective function for trust region algorithm is introduced. Finally, the optimization problem of the objective function by genetic trust region algorithm to get the inverse kinematics solutions of mobile manipulator is solved. Simulations show that the method can quickly obtain precised and optimized inverse kinematics solutions.
A position and traffic based routing protocol for vehicular Ad Hoc networks (VANETs) in city is proposed with using real time traffic information and mobility prediction to forward data with the idea of “carry and forward”. The protocol can work well where the destination node is moving. Simulation result shows that, compared with greedy perimeter stateless routing (GPSR), it achieves good delivery rate improvement and lower delay.
Clustering is the most popular method to impose a hierarchical structure in the mobile Ad Hoc networks. However, the formation and maintenance of a hierarchical structure depends on certain clustering algorithm. By studying existing clustering algorithm, a new on-demand weighted clustering algorithm (NWBCA) is proposed. The optimized connectivity degree and energy status of mobile nodes are taken into consideration. The adoption of the on-demand strategy improves the stability of the network architecture and lowers the computing and communication cost. By investigating the performance of the proposed algorithm with that of others, the simulation indicates all the specifics of NWBCA are superior to those of the other and the validity of NWBCA has been proved.
To quantitatively and comprehensively evaluate the network reliability of the whole PON, a new passive optical network (PON) reliability model is proposed. It can indicate the failure's effect on the network or the different contributions of different nodes and links. Based on this model, the network reliability and cost of PONs in typical optical network unit (ONU) location situations with typical topologies are analyzed, the optimized location of splitter in one-splitter tree PON and trunk-protected tree PON is given.
The low-energy adaptive clustering hierarchy（LEACH）for wireless sensor networks prescribes that each cluster head sends fused data directly to base station, so cluster heads that are farther away from base station consume more energy, resulting in unbalanced energy consumption of the entire network. A data fusion oriented clustered routing protocol based on LEACH is presented to reduce the energy consumption of the cluster heads and to balance the energy consumption of the entire network. In this protocol, a cluster head estimates which neighboring clusters also sensed the same event by the locations of its member nodes during intra cluster data fusion process; data is fused among these cluster heads hop by hop before transferred to base station afterwards. Simulations show that this protocol can effectively prolong the life time of the sensor network.
In order to reduce great overhead of ondemand multicast routing protocol （ODMRP） in multisource applications, an improved flooding limitation mechanism ispresented, which permits forwarding nodes and backup nodes to transmit maintenance packets only. It makes good use of broadcast characteristic of wireless channel and periodical routing maintenance of ODMRP. Simulation shows that this improved ODMRP is especially fit for multisource group communication and less receiver occasion compared to the network scale. Under the above conditions, the protocol reduces maintenance overhead effectively and enhances packet delivery ratio（PDR） distinctly.
Two limited factors in time division duplex (TDD): capacity loss caused by roundtrip delay in sole cell, large region wireless region access network (WRAN) system and performance degradation caused by co-channel interference in multi-cell environment are analyzed. In WRAN
system, capacity loss was reduced by signal transmission in idle time on the basis of distance between customer premises equipment (CPE) and base station. Simulation results show that uplink capacity increase at least by 5%. In multicell system, an improved time slot allocation method is put forward. It shows that at 1% outage probability, 11～12?dB signaltointerference ratio (SIR) performance is improved compared with no optimization situation, and 2.5～3?dB performance is degraded compared with original time slot allocation method, but system complexity is reduced to (M2-M)/2.
In unstructured peer-to-peer networks, there are numerous malicious nodes, whose false behaviors decrease the efficiency and reliability of the search．A resource discovery approach based on the trust and social networks (TSN) is proposed to solve this problem．Forwarding trust, routing trust and transaction trust are set up to reflect the credibility of the peers．When a peer node selects friends to forward the query message, the friends with high trust and correlation will be given priority. Simulation shows that the TSN effectively screens out the malicious nodes and improves the resource reliability and the searching efficiency.
In order to improve the relay delay and successful relay probability performances of high frequency token protocol (HFTP), derived from HFTP token relay protocol，a distributed collisionfree token relay protocol named sub queuedynamic token relay protocol (SQDTRP) is presented, Through the introduction of the communication object column in the relay subqueue, the realtime network status are reserved as much as possible for the dynamic searching of token relay paths. As a result, potential collisions in acknowledgement to SOLICIT-RELAY and the token passing impartiality problems are well corrected by this protocol. Simulations indicate that the token relay delay and token relay success probability of SQDTRP are better than HFTP, which makes it very suit for high frequency (HF) network and other kinds of wireless networks, too.
According to the track performance of adaptive filters with poor performance in
rapid fading channel, an adaptive filter principle based on capability control a
nd semiblind technology is presented. And a semi-blind equalizer based on con
stant modulus characteristic and structure risk minimum (SCM-SRM) criterion is
designed. The information of communication signals learning should sufficiently be dug. On the other hand, the structure information of oneself of filters shoul
d also sufficiently be dug (by use of a capability control method). In a word, t
he track performance of filters is improved by maximizing amount of learning information. Simulation is carried out that compared with a typical recursive l
east squares equalizer and a constant modulus semi-blind equalizer, SCM-SBE has better track performance in much less training data, and adapts for wireless motion communications.
A new approach of vibration environmental prediction on mechanism is presented to study the vibration characteristics of moving flexible joint robot. Taking a 3-D manipulator robot as the research object, this method combines wave theory of structures with rotated transform matrix of joint. Considered the general force balance and displacement boundary of each joint, the environmental prediction model of system in moving states is established. Vibration experiments on moving robot are done. It is shown that the approach is feasible.
To solve the problem of route matching delay in the core routers, an unclassified Internet protocol (IP) address mode, classless inter-domain routing (CIDR), is introduced. By analyzing the CIDR list and referring to the non-keyword index method and the partitioned indexing algorithm in databases, a novel B-Tree algorithm with nonkeyword index which satisfies the requirements of the CIDR list is brought forward. This algorithm firstly makes a partitioned index on the set of all the prefix addresses in the CIDR list. Being partitioned, the CIDR list is changed into a B-Tree index structure. Then the algorithm does fast lookup in the CIDR list according to the non-keywords of the IP addresses. Simulation shows that the new algorithm meets the demand for the IP address fast lookup.
To detect moving shadow in intelligent video surveillance system, a method using illumination invariants c1c2c3is presented. Firstly, the coordinate
systems are defined on the basis of c1c2c3ratios of foreground and b
ackground pixels at the same position. Secondly, the moving shadow detection can be treated as a classification problem of shadows and moving objects in abovementioned coordinate systems. An ellipsoid is further constructed according to the scattering feature of shadow pixels. All the pixels inside the ellipsoid are extracted as shadows. Finally, the postprocessing is performed by exploiting the geometrical property of shadows. Experiments show that the proposed algorithm is robust and effective in detecting shadows for a variety of scenes and moving objects; moreover, it is suited for varying illumination conditions.
A precoding method utilizing interference is proposed in multiple-input multipl
e-output broadcasting system (MIMO BC) in which each receiver has one antenna. This method turns a multi-user system into a number of independent two-user or one-user systems. In two-user system a new model based on vector is established，and with the objective of maximizing system capacity the optimal precoding vectors and power allocation are derived. Simulations show that the proposed method has the similar capacity with minimum mean square error (MMSE) precoding but reduces complexity with about one-third of MMSE's complexity.
A method of frequency hopping (FH) co-site interference cancellation using community antenna and pilot (CAP-FH-AIC) is proposed according to the analysis of the characteristic of the FH co-site interference. The structure of the canceller is transformed from multi-reference adaptive FH co-site interference cancellation (M-AIC) to single-reference adaptive fixed-tuned co-site interference cancellation (S-AIC) only by adding an additional generator of the pilot signal and an additional band-bass filter. It can realize the cancellation of the FH co-site interference and get almost the same performance of the adaptive fixed-tuned co-site interference cancellation. The theoretical inference and simulation confirm that the algorithm can get the advantage of steady performance in FH co-site interference suppression.
Since most of the known multivariate public key signature schemes are
under attacks, an improved signature model is proposed by analyzing the structure of the classical model. The method to redesign the model is to add another secret transformation so that the public key polynomials are not corresponding to the composition of the private keys, that is not the case in classical model, and the message value is hidden, then the amount of information obtained by attacker are reduced, and the scheme performance against attacks is enhanced. Analysis shows that the improved model can strengthen the security of various multivariate signature schemes. Finally, medium-field extension (MFE) multivariate cryptosystem is taken as an example to illustrate the idea.
To make sure the assessment accuracy, an efficient algorithm with qualitative analysis and quantify calculate is described. To collect the data, the algorithm chooses the operationally critical threat, asset and vulnerability evaluation (O
CTAVE) method, defining the assets which need to be assessed, evaluating the administrant and technical vulnerabilities. To calculate the risk, grey theory is chosen, and triangular whiten weight function is used to compute the membership degrees, the risk level is then determined. This valuable method can be used in practical operations of information security risk assessment.
Some new call admission control schemes in orthogonal frequency division multiplexing access (OFDMA) relaying cellular system are investigated. Subjected to hard constraint on the quality-of-service (QoS) requirements, the capability of relay, the user's selection of relay and the competence among users, these schemes enlarge the amount of subcarriers saved by two-hop transmission of each relay as much as possible, thus enhancing the resource utilization and system capacity. Simulations verify the effectiveness of the proposed scheme.
A partners choice algorithm is proposed based on cooperative multi-input multi-output (MIMO) transmission in energy-constrained sensor networks. Compared with existing work, the distributions are that the cooperative nodes choice in every transmission is not based on minimizing energy consumption but balances residual energy between participant nodes including source node. The efficiency of the proposed algorithm by simulation is validated when comparing with the direct transmission and minimizing energy consumption transmission.