- EI核心期刊
Network convergence has become an important process and component of broadband strategy. Network convergence is aimed at promoting the information processing capacity and making china to be a network power. The connotation of network convergence is discussed, the domestic and international current status is introduced, the respective advantages and disadvantages of Broadcast & Television are analyzed, the key technology of network convergence, architecture of next generation network and problems of network convergence are presented, and the direction, goal and strategy of network convergence development are proposed.
A 4×10Gbit/s optical timedivision multiplexed (OTDM) 100km transmission system with homemade multiplexer is implemented utilizing the clock recovery module combined with the sampling window of electrical absorption modulator (EAM). Errorfree demultiplexing is achieved experimentally. Dispersion and dispersion slope compensation are implemented simultaneously under the conditions of compensationinmiddle or compensationinend. And the power penalty is approximately 08dB and 065dB respectively after transmission.
Lightpath connection provisioning problem for capacity upgradeable transparent optical networks with hybrid line rates, modulation formats and dynamic dispersion compensation characteristic are investigated. Two impairmentaware routing, wavelength and compensation assignment algorithms are proposed. Simulations show that the proposed algorithms can improve the network performance significantly with much lower blocking probability, compared to the existing impairmentaware routing and wavelength assignment algorithms.
To meet the requirements of multigranularity optical networks for capability of switching at different granularities, a resource preconfiguration strategy is introduced into multigranularity optical networks. By preconfiguring the resource of multigranularity optical networks, the topology can be reconstructed with the number of direct routes increasing. The performance of routing and forwarding can be optimized. Numerical simulations show the connection establishing time of control plane could be significantly reduced by using resource preconfiguration strategy.
Different fashions of power supply have different power prices. In order to reduce power cost in mobile communication network, an algorithm is proposed to minimize the outage probability based on power cost. It subjects to the constraint of power cost. The Lagrange multiplier maximization method is used to solve the problem. Simulation shows that whether dualhop or multihop transmission, the power prices of different nodes are not the same, the optimal power allocation based on power cost has lower cost compare than the optimal power allocation in the case of uniform outage probability. Whereas, the former has lower outage probability in the case of uniform power cost. The contrast is more obvious with the gap of power prices enlarges.
In order to obtain space diversity to fight channel fading, a transmit diversity scheme applicable to frequency selective channel is proposed. With zero correlation zone complementary codes, both full space diversity and full frequency diversity can be obtained. Simulation proves this scheme has same performance compared to original diversity design in frequencyselective channel presented by previous research. Its transmitter and receiver structure are much simpler than the previous one, and shows more flexibly.
The symbol error rate (SER) performance is analyzed for the optimization of amplifyandforward multinode cooperative communication systems. Firstly, theory SER is analyzed for the systems. Then, the corresponding low bound (LB) is derived, that will be nearing the theory SER between both low and high signaltonoise ratio conditions. Finally, algorithms used in optimal power allocation (OPA) and partnership selection for the systems by exploring the LB as cost function are formulated. Theoretical analysis and simulation results show that the OPA outperforms traditional equal power allocation in SER performance. Moreover, the LB will be more nearing the theory SER than existing algorithms especially under low SNR conditions.
For the problem of intercarrier interference in orthogonal frequency division multiplexing （OFDM） signals of cognitive radio systems, a coding method for enhancing spectrum notch of OFDM signals is proposed. The same dates are transmitted on the two adjacent subcarriers, and then weight the dates on the two adjacent subcarriers to make their sidelobes cancel each other out at the frequency of spectrum notch, so as to reduce the power spectrum at specific frequency. Theoretic analysis and simulation results show that, not only the method can enhance the spectrum notch but also has a good performance of antinoise.
Closed-form expressions of outage probability is derived for multiple-input multiple-output (MIMO) relaying channels with transmit antenna selection/ maximal-ratio combining in two-hop nonregenerative relay networks operating over nakagami fading channels. The effects of fading parameters and antenna con?guration on the overall system performance are analyzed and discussed through representative numerical examples. Simulation results show that channel quality of the first hop link in nonregenerative MIMO relaying system plays a major influence on outage performance.
To improve the accuracy of evaluation on IEEE 802.11a data service supporting capacity and guide network planning work, a modified twodimensional Markov chain model of the backoff window scheme is proposed. By analyzing the IEEE 802.11a wireless local area network (WLAN) system performance in the aspect of framing efficiency and distributed coordination function (DCF) efficiency, the normalized system throughput and average packet delay under the condition of saturation are found. On the basis of that, the handoff thresholds for basic access mode and request to send/clear to send (RTS/CTS) mode for diverse number of nodes are given, thus the system performance is optimized.
A honeycomb (nonsquare) 16 amplitude phase keying (APK) modulation is proposed. A new dualmode based on honeycomb decision region algorithm (DHDRA) is provided. The proposed algorithm is simulated using a typical shallow underwater acoustic channel. Simulation shows that, more antiinterference and faster convergence are achieved with the constant modulus algorithm (CMA) based on the honeycomb 16APK than that with the square 16QAM, meanwhile. Also, higher convergence speeds and less steady residual errors are got with the proposed dualmode algorithm than the that with the squared decision region algorithm. They have the research value for improving the underwater communication qualities and decreasing the intersymbol interference.
Within cells of cellular system, the mobility of relay terminals causes the cooperative relay channels instability, brings frequent interruptions to multicast stream. To solve this problem, a layered relay multicast scheme with highcapacity and continuity of multicast service is proposed. Based on a layered abstract model and a nonfading wireless model for satisfying the scheme, the capacity of layered multiple relay channel is studied. Analysis and simulation show that the scheme guarantees the continuity of multicast service when compared with general nonlayered relay networks, though it causes a slight loss on capacity.
The problem that the existed resource allocation strategies cannot give integrative consideration to quality of service (QoS), frequency efficiency for mixed traffic scenario is stated. And a utilitybased resource allocation strategy for wireless networks from practical utilization aspect is proposed. The unified utility function for users with different traffics is studied firstly. Secondly, the resource allocation strategy based on this unified utility function is analyzed in mixed traffic scenario after building and analyzing the optimization model. This strategy can automatically guarantee the QoS requirement for realtime traffics and the tradeoff between throughput and fairness for users with best effort traffics through utility function. Numeric simulation indicates that this strategy is very applicable for mixed traffic, and the resource requirements for QoS users can be satisfied preferentially in mixed traffic scenario.
For mobilecommerce environments, a novel passwordbased authenticated key exchange protocol is proposed to solve that the technology to effectively prevent legitimate users’ abuse, named as completely automatic public Turing test to tell computer and human apart (CAPTCHA), is vulnerable to analytical attacks. The protocol elaborately combines the CAPTCHA challenge/response progress with the authenticated key exchange interaction. It introduces symmetric encryption scheme to make CAPTCHA secure without additional communication rounds. And it is based on smartcards to obtain stronger security and adopts elliptic curve cryptosystem which is suitable for the environments. In random oracle model it is provably secure. Compared with the other related protocols, it requires only three communication rounds, protects CAPTCHA against analytical attacks, needs no validation tables storing on the server and provides perfect forward secrecy.
To decrease feedback overhead, a phase rotation precoding for orthogonalized spatial multiplexing (PROSM) system is proposed, in which a proper rotation is set at the imaginary part of modulated signals. Compared with the power allocation precoding of OSM (PLOSM), the feedback information of this scheme is decreased and the complexity of calculating precoding parameter is also reduced. Simulation results show that with the same reliability of PLOSM, the proposed scheme saves four bits feedback overhead.
The secret sharing schemes are important techniques for key management. However, most verifiable multisecret sharing schemes can not distinguish the security classification because of having the common drawback of sharing secrets with the same value. A verifiable multipolicy secret sharing scheme is proposed. The significant character of the proposed scheme is that each participant has to be kept only one master secret share, the share can be used to reconstruct different group secrets according to the number of threshold values. So it will reduce the calculated amount of the secret distributor. Moreover, the efficient solutions against multiform cheating are proposed, the scheme is therefore with highly security and practicality.
Cubic extension Bézier (CEBézier) curve with multiple shape parameters is one of the most important extensions of the cubic Bézier curve. It not only inherits the outstanding properties of the cubic Bézier curve, but with a good performance on adjusting their local shapes by changing the shape control parameters. In order to develop the basic theory of CEBézier curve, a new method to deal with approximating two adjacent CEBézier curves by one CEBézier curve is presented for the approximate merging of existing curve design. By combining the fitting method of curves and the theory of the general inverse matrix, the explicit formula of control points of the merged CEBézier curve can be given directly. Eventually, some merging examples are discussed and the errors of approximate merging are given as well. Experiments illustrate that the proposed method not only has a good merging effect, but is easy to implement and simple to error estimation.
The coupling coefficient of twincore fiber (TCF) is discussed. It is shown that the coupling coefficient is related with the input signal wavelength, the core diameter, the distance between the centers of the two cores, and the relative refractive index difference. The parameters of the twincore fibers can be optimized to satisfy different requirements. The twincore fibers are fabricated. From measurement, an obvious progress is shown better than the previous work.
The GaNAs strain compensation layers for the growth quality of the InAs/GaAs quantum dots stack in quantum dots verticalcavity surfaceemitting lasers (QDVCSELs) are investigated. The influences of different concentrations and locations of the compensation is obtained. The approach in determining the optimal compensation parameters is also achieved. We give instructions in fabricating the QD active region in QDVCSELs of long wavelength (12-16μm).
The initial credit scoring of telecom customers for different arrears rates is studied to improve the fairness and reasonableness of credit scoring. Using genetic algorithm and ant colony algorithm respectively, the weights of the customer attributes with respect to the credit are obtained to mine important knowledge from the customer data sets with different arrears rates. A credit scoring model added evaluation factor is proposed in order to find the optimum solution of credit weights in the case of high rate of arrears. Experiments indicate that it is necessary to select different scoring algorithm or different scoring model for the group with different arrears rates.
The performances of cooperative spectrum sensing with equal gain combination over Nakagami channels are analyzed in cognitive radio networks. The series form of detection probability is derived by transforming the multiple integral to a single integral and using the equivalent representation of generalized Marcum Qfunction. Simulation shows that the correctness of the theoretical analysis results are validated, and a group of practical parameter settings is given. Parameter selection for designing cognitive radio networks can be provided by expressions of detection performance.
A handover decision method for cognitive networks is investigated in the context of wavelet and pattern recognition. It follows two steps: firstly, making multiresolution analysis to the signal received in base station to get the basic signal and the noise signal. Secondly, making the pattern recognition and handover decision by artificial neural fuzzy inference system. Simulation shows that it greatly improve the system’s performance when the channel is in low signaltonoise ratio. Besides, it makes the system cognitive and adaptive to the changes of the environment.
A method using postfunction information (PFI) is presented, in order to improve the precision in software static testing. The PFI includes local modified set and global modified set used to model the effect on data flow under testing. An algorithm to generate PFI by using control flow iteration for each function is proposed as well. The generated PFIs by the algorithm can be used in the phase of interval computation and defect pattern detection. Applications in defect detect system verifies the feasibility of this method.
Based on the transmittedreference impulse radio ultrawideband (IRUWB) system, a new codeorthogonalized transmittedreference chirp UWB system is proposed to meet the needs of UWB application with increasing transmission distance. Referring to the dechirp methods in radar system, it designs an active spectrum compressed structure for the receiver. Analysis and simulation show that this system has both the advantages of transmittedreference IRUWB systems and chirpUWB systems. Furthermore, the analog matched filter and highspeed analogtodigital converter are not required, but facilitate system miniaturization, low powerconsumption and integration design.
Focusing on the requirement of trust management in multiAgent systems, the sarsa reinforcement learning (SRL) theory is applied to construct trust prediction model for multiAgent systems based on Agent’s behavior. First, basic formal description is conducted for trust decision, and behavior statespace structure is constructed based on timestamp according the interaction time sequence between network Agents. With SRL algorithm, overall trust relationship predicting model based on direct trust degree and feedback trust degree is proposed. The model makes full use of the advantages of the strong dynamic adaptive capacity of the SRL algorithm, brakes away from the inadequate dynamic adaptive capacity in the traditional software trust modeling process. Simulation in cumulative errors shows that, compared to the existing models the new model has remarkable enhancements in the trust decision accuracy.
In distributed Hash table（DHT）based peertopeer（P2P）systems, the use of DHT and the heterogeneity of nodes’ capacities may give rise to load imbalance problems, and affect the DHT system efficiency as well. A new load balance algorithm, static load distribution algorithm and dynamic load adjustment algorithm (SDYA) is presented, it adopts the concept of virtual server. And the algorithm assigns rational load and corresponding address space that can be dynamic regulated to every peer in P2P. Through research and simulation analysis, compared with the traditional virtual server loadbalancing algorithm，the SDYA algorithm is with better load balance, faster velocity of load balancing, less load movement cost, and more excellent stability of P2P system.
Aimed at the problem that the node correlation in network is not considered in hidden Markov model (HMM) network risk assessment, combining graph theory model, the network node correlation (NNC) state transition matrix is built. With the intrusion defective system(IDS) alert as input, using modified HMM model the attacking route is figured out. Furthermore, the successful probability of any attacking sequence with any length can be got as well. The method can help to find vulnerabilities of network nodes, and reflect network risk well. Experiment demonstrates the validity of it.
In order to improve the system performance for vehicletovehicle communications over doubleRayleigh fadings, the accesspoint relayed intervehicular communication (IVC) model is proposed. The statistical properties of the receiving signaltonoise ratio in IVC system are studied and a closedform expression on outage probability is obtained. And based on moment generating function method, the union upper bound on average bit error rate (ASER) is derived. Simulation results show that the theoretical analysis on outage probability coincides with Monte Carlo numerical calculations well. The ASER of the relaying IVC system is decreased and the diversity gains are achieved 3dB more at most through optimal power allocation method than equal power allocation scheme.
The degree distribution is key index to evaluate the performance of Luby transform (LT) codes. In order to obtain a better degree distribution, a degree distribution optimization method is proposed. By using ant colony algorithm and Monte Carlo simulations, some statistical parameters are selected as optimization target values. By searches of ant colony algorithm, optimized degree distribution could be derived. Compared with the actual decoding performance of optimized degree distribution according to simulations, the effectiveness is confirmed that can achieve the optimization target values by statistical parameters from Monte Carlo simulations.
For supporting large number of transmit antennas in macro diversity transmissions, a highdimensionfullrate (HDFR) quasiorthogonal spacetime block code (QOSTBC) is proposed. The new code operates at full rate, and the maximum likelihood decoding complexity is controllable. The equivalent channel matrix of this code is analyzed. It is concluded that the eigenvectors are constant and independent from the real channel realization. Furthermore, a new preprocessing transmission strategy with singlesymbol linear decoding complexity is given by exploiting the revealed characteristic of HDFR QOSTBC. Simulation shows that the proposed strategy is of more advantage for macro diversity comparing with minimum decoding complexity code and cyclic delay diversity.