- EI核心期刊
A new approach to model service traffic and performe anomaly detection on TCP/IP backbone in the perspective of periodic traffic feature was proposed. This method avoids the difficulty to model the uncertainty and nonlinear facts in traffic data and provides more accurate information than the thresholds based detection method.
Trust management was discussed according to security requirements in distributed environment. A graph based delegable model and its formal description were given. Permissions propagating control, conflict and cyclic in delegable model were analyzed and resolved. Finally, the scheme of determining access request of subject in distributed environment and future work were proposed.
ZPOFDM(zero padding orthogonal frequency division multiplexing)has the disadvantage that the simple FFT (fast fourier transform) based receiver does not perform well. Therefore, a pseudorandom sequence processing technique that is each row of the IFFT (inverse fast fourier transform) matrix multiplies with a bit of a pseudorandom sequence is proposed. The technique changes the correlation properties of the IFFT matrix columns, and hence improves the performance over multipath channels. The modified IFFT matrix is still unitary and orthogonal, since the multiplication by ±1 of the IFFT unitary matrix rows doesn't destroy its unitarity and orthogonality. This technique is analized theoretically and applied to ZPOFDM, ZPOFDMOLA and ZPOFDMFAST. Simulation results verify the improved performance of the modified methods using this technique. The Hiperlan2 Channel models A and E are considered in our simulation. For the two channel models, the modified methods exhibit at least 22?dB advantage in SNR at 10-4 BER （bit error rate）.
In order to improve the transmission performance in intersymbol interference (ISI) channel, high rate lower order modulation transmission with ISI was studied and the error rate performance of lower order modulation and higher order modulation with the same message rate and band width was compared. High rate lower order modulation transmission with ISI makes full use of the potential anti jam capability of the system and the threshold signal to noise ratio is greatly decreased by more than 10?dB. Simulation results show that with the same message rate and band width, lower order modulation transmission, interfered by ISI and employing sequence detection, obtains greater performance gain than higher order modulation, which is not influenced by ISI and detected symbol by symbol.
A new algorithm of joint transmit and receive optimization based on the practical need of the communication system was put forward. The new optimization algorithm could optimize the MIMO spatial multiplexing system to minimize the symbol error rate with the constraint of a fixed transmit power and data rate. The whole MIMO spatial multiplexing system could be decomposed into several independent parallel subchannels by the optimized transmit and receive filter. And modified Fischer's loading algorithm could be applied into these subchannles according to the new algorithm of joint transmit and receive optimization. Eventually, the optimal transmit power allocated to these subchannels were achieved. The analysis results are consistent with the simulation results. The lower the rate is, the better performance will be achieved in the same MIMO spatial multiplexing system with the same SNR; the more antennas the system has, the better performance will be gained with the same rate.
Distribution characteristics of the response time in transaction processing systems were studied and analyzed. The conclusion shows that the mean response time goes by the exponential trend with the change of the call intension. A linear regression method was proposed for the first time to detect automatically the overload detection point of the transaction processing system. It implemented overload detection adaptively according to the load of systems, and was independent of system structures. The results of the experiment show that this method applied in an adaptive window control algorithm of the intelligent network service contr ol point has good adaptability and validity.
The optimal value of the TCP(transport control protocal) data sending rate was studied when the wireless channel was in bad state. Two algorithms to adjust the size of TCP CWND(congestion window) were presented. The target of most research on TCP in wireless network is to improve the throughput. So the size of CWND doesn’t decrease when the packet loss is due to corruption. The result is the decrease of the reliability of TCP when the heavy packet loss rate occurs. The requirement of throughput and reliability were studied. The simulation results demonstrate that the QoS(quality of service) requirement is met and the throughput is not declining greatly.
The effects on capacity complementary cumulative distribution functions (CCDFS) of multiple input multiple output (MIMO) channel caused by the different antenna array structures and indoor propagation environments of both line of sight (LOS) and nonline of sight (NLOS) cases are analyzed by using a 2D SBR (shooting and bouncing) ray -tracing method. Antenna array structures and indoor propagation environments affect the CCDFS significantly. 10% outage capacities show that in both LOS and NLOS indoor environments, there exist a fixed relationship that independent and identically distribution (i.i.d.) rayleigh channel capacities are larger than the capacities equipped with linear antenna array which are larger than the capacities equipped with rectangular antenna array or capacity equipped with circular antenna array. And the capacities of NLOS MIMO channel are larger than the capacities with LOS path. The results show these conclusions are very useful for designing MIMO system.
The mutual performance influence in different load cases about softswitch service and web service in the Parlay multi-service environment were studied. The dynamic resources allocation method between these services was proposed. Taking the stability of system as the prerequisite, SSDB (session setup delay bound) mechanism was proposed to satisfy each service's performance requirement on throughput and average response time. The simulation results prove that dynamic allocation of the system resource based on SSDB can satisfy each service's performance requirement in this environment.
TCP (transfer control protocol) performance in OBS （optical burst switching） network was studied, and the performance degradation of TCP tahoe, reno, new reno and sack in the OBS network was discussed. Considering the ACKs' (acknowledgement) losses, a simple analytic model was investigated to give the steady state TCP throughput over the OBS network. The simulated result demonstrates that the model can accurately predict TCP throughput over a wide range of loss probabilities. The impact of ACKs' losses was analyzed based on the calculation results. Besides, ACKs were suggested to be treated as a kind of high QoS data in OBS network.
Internet interconnection settlement was studied to promote Internet development and to make out reasonable interconnection policy. Different Internet backbone providers have different preferences of interconnection quality. The larger backbone prefers a lower quality of interconnection than the smaller backbone does. The best level of connectivity should be intermediated between what would be optimal for each backbone from the point of society. Under these circumstances, the smaller in general bribes the larger network to accept a higher level of connectivity, which is also Pareto betterment. Introducing the focal point equilibrium, two backbones determine interconnection quality through bargaining, which decreases exchange cost and regulatory cost.
A grope research is described on specific application domain oriented Chinese Information Extraction System from the point of Comprehensive Information Theory. A Comprehensive Information Knowledge Base is built through defining, analyzing and using syntactic, semantic and pragmatic information as an integrated entity. An experimental demo system is implemented for the application domain of financial news about management leaders' alteration in companies. Based on this, a kind of application model is discussed for information extraction system in Intelligent Mobile Information Service, which is Information Extraction plus Mobile Short Message Service. We assembled the characteristics of conciseness, definiteness in focus of Information Extraction result with that of mobility, facility and popularity of mobile phone into an experimental system. Testing results have shown its feasibility.
The lattice reduction (LR) aided schemes were adopted in the zero forcing (ZF) algorithm (LR ZF) in rich multipath mobile communication environments of code division multi-access (CDMA) systems. The performance of LRZF was simulated and analyzed in LASMAX systems. The results verify that the systems' performance is improved highly, particularly in high SNR, at the expense of a little complexity increase. So LR algorithm can be adopted in mobile communication systems with multipath channel.
The elastic strain fields in the 2×2 array self-organized coherent quantum dots (QD) structures were investigated in detail by the finite element analysis for lens QDs. Strains of quantum dots array along different directions at different height in QDs were presented. Conclusions show that the strain of QD will not be influenced by the other of the QDs array when the size is similar to the distances between the QDs in the array.
The M/G/1 queueing system with fixed times of feedbacks was expanded to a genera lized situation, i.e., every customer accepted total m times of services, and the distribution function of every service time was different from each other. A customer on hisith service was regarded as a classCicustomer. The Laplace Stieltjes Transform of the total sojourn time of a customer defined as the duration from the customer arrival until the departure from the system was presented. Therefore, a useful tool is provided for modeling analysis of communication systems.
A multiple access method based on complete complementary codes in UWB (ultra wideband) communication was presented. The zero crosscorrelation of complete complementary codes ensured it as the signature code about user. The decoding of the receiver employed the algorithm about shift and add to decode the intended user's information. The principle of the proposed receiver and the reason why the receiver could suppress multiple access interference (MAI) were illustrated. The performance analysis and simulation results show that the proposed multiple access method based on complete complementary codes can accommodate better performance on suppressing MAI than THPPM UWB system.
The routing and wavelength assignment (RWA) problem in WDM(wavelength division multplexing) all optical networks was studied. A novel adaptive routing and wavelength assignment algorithm, the minimum path weight first (MPWF), was proposed. Simulation result shows that compared with previously proposed RWA algorithms, the MPWF algorithm achieves better performance under uniform and non-uniform traffic models.
Based on the system feature of softswitch based heterogeneous clustered media server, this paper proposed a limited resource vector load balancing algorithm and also provided its software implementation method. Harmonious usage of system resources was considered and violent shaking of the system performance was avoided in the algorithm. A lot of simulations on the Petri net model of balance system had been conducted and the algorithm had been compared with some traditional algorithms on system throughput, request response time and performance stability. Results of simulation experiments show that the algorithm has higher performance. The implementation method of the algorithm is also useful for other heterogeneous clustered systems.
A Transmit Preprocessing Technique for Downlink Spatial Multiplexing in Multi-user MIMO Channels was proposed. Through adding additional constraint to the joint TxRx MMSE optimization scheme the equivalent channel could be changed from block diagonalization to complete diagonalization. MUI (multi-user interference) and per user multi stream interference could be canceled simultaneously. The modified algorithm is much more feasible and has the advantage of simplifying the receivers. A general complete diagonalization is the channel inversion algorithm. Performance analysis and comparison prove the complete diagonalization algorithm proposed has better performance than channel inversion algorithm.
In order to investigate the interference distribution in time division duplex code division multiple access (TDD CDMA) system, the difference of interference distribution between TDD CDMA and frequency division duplex (FDD) CDMA systems was investigated. By introducing smart antennas, the inter to intra cell interference ratio in CDMA systems was deduced. And taking TD SCDMA as an example, static and dynamic system level simulator was established to validate the conclusion of theoretical analysis. Simulation results show that sector antenna and smart antennas can reduce the inter to intra cell interference ratio effectively and slow dynamic channel allocation scheme is also able to weaken the inter cell interference in TDD CDMA systems.
A novel scheme based on traditional electronic codebook (ECB) mode was proposed to improve the capability of block cipher mode of operation. Message blocks were masked with the Gray code so that the data mode was hidden efficiently. The security of the scheme was analyzed in the sense of reduction based cryptography. Investigation shows that the scheme is left or right indistinguishable against chosen plaintext attack (LOR CPA) secure if the underlying block cipher is a pseudorandom permutation.
For management telecommunication services, the concept of impersonal degree of telecom services' satisfaction is defined based on Qos (quality of service) KPI by using attribute set mathematics theory in the paper. And a telecom service quality model is designed based on theory of man' brain apperception. At last the quality of MMS (multimedia message service) is analyzed with the model.
A novel multi ASes topology discovery algorithm was proposed, which could infer the AS information of all non-BGP (border gateway protocol) routers from that of the nearest BGP router. The algorithm could efficiently and accurately discover the AS layer and the network layer information of the network, including ASes, adjacent relationship between ASes, routers within each AS, subnets, and network devices within each subnet. The algorithm was validated in a large scale carrier class IP trial network. And it could not only be used for traditional network management, but also be used for quality of service management to provide a more accurate and complete network topology.
Audio watermarking algorithm based on discrete wavelet transform (DWT) is proposed in this paper. The algorithm embedded watermarking by quantizing the lowest frequency coefficients of DWT of the digital audio signals so that it is more robust than the algorithms introduced previously. The idea of embedding synchronic signal which used the synchronic signal to search the watermark location was introduced. The experimental results indicate the algorithm is robust to many operations on digital audio signal, such as Guassyawp, lossy compression, requantization.
A service interaction management system framework was proposed based on analyzing the similarity of biological immune system and service interaction detection. In this framework, the trigger event was mapped to the antigen; the output of service logic response to trigger event was mapped to immune response; service interaction was mapped to abnormal immune response; and the resolution of service interaction was mapped to immune adjust. Through these mapping rules, different service interaction detections and resolutions are no longer isolated, but can be integrated.
Based on the analysis of existing 3G (3rd generation mobile communication system) service creation drawbacks, a model driven, automatic service creation approach for 3G through using Model Driven Architecture's viewpoints separation idea was proposed. The constructing methodologies of service requirement analysis model and telecom service domain related meta model were elaborated in detail. This service creation approach provided an innovative telecommunication service development mode. This mode separated service function specification model from concrete open API technologies and implementation technologies, and supported domain model shared. As a result, this approach enhances the abstract level of 3G service development, decreases the technical threshold and shortens the service development cycle. The portability of service function model across different open API technologies and implementation technologies is strengthened. Service development and maintenance cost is reduced.
Software reliability is an important parameter to evaluate software, and post development evaluating methods are commonly used. Based on the present hierarchical component system reliability model, the relativity between the components in the same level was studied. A fairly applicable and hierarchical component matching software reliability evaluating model was proposed and extended to a common component based software reliability evaluation model. With this model, software reliability can be forecasted during the development process, and can estimate part of the IPv6 protocol stack software's reliability.
Drawing idea from the quantum secure direct communication (QSDC), a novel quantum secret sharing (QSS) scheme with high efficiency based on Bell states was proposed. In this scheme, the sender Alice needed no longer share a joint key between her and the two receivers, Bob and Charlie, as well as used the joint key to transmit her message. Alice shared her secret message with Bob and Charlie directly. One Bell state could be used to share two bits message. Investigation showed that the scheme is secure.
Random delay anti-collision algorithm was discussed for digital processing central module in RFID (radio frequency identification) system, and condition of system stability was given based on mathematic analysis. The related research on key technology，data security technology was studied in detail，and a communication system including data encryption and error correction was designed. The research and design of digital processing central module in read/write device were proposed，and the plan for new research and development was drawn up.