- EI核心期刊
A real time service overlay network (RSON) is presented in this paper. It can offer QoS(quality of service)sensitive transport service on Internet to facilitate the newly emerged real time multimedia applications. The RSON system consists of a collection of service nodes, deployed at various locations on Internet.These services nodes are connected together by servic e links, which corresponding to underlying IP paths, form an virtual transport network on top of existing network infrastructure. The most important feature of RSON is that, it requires no changes at the network layer and its business practice. To ensure the desired performance of every overlay service flows, the distributed service nodes in RSON all participate in an overlay service routing protocol (OSRP). The OSRP includes measurement of service links; link states dissemination; path selection and setup; and an associated data forwarding module. As a virtual transport network over the underlying data networks, the RSON empowers the third party providers to offer value added service on Internet to its customers. Using VoIP application as an example, we illustrate how to provide enhanced network service on Internet and identify the tangible benefits it generates.
A new self-adaptable failure detection algorithm is proposed in this paper based on the premise that the delay and loss of the heartbeat information is a random probability. This algorithm can realize the random accuracy requirement and adapt itself to the change of network environment. The test result shows that this algorithm can effectively decrease the error and detecting time will not grow because of the decrease of error. Therefore, it is very effective.
A new mutual coupling calibration algorithm is presented to estimate the mutual coupling coefficients of uniform circular array. Firstly, the signal subspace vector including information of mutual coupling coefficients is expressed as product of mutual coupling coefficient matrix and perfect array steering vector. In accordance with transform formula between mutual coupling coefficient matrix and perfect array steering vector, the independent elements in mutual coupling coefficient matrix can be expressed as a column vector. Based on least condition number rule, the column vector is given by the matrix inversion. Simulations demonstrate accuracy for estimation of the mutual coupling coefficient matrix and the stability for error perturbation of the algorithm.
The M/G/1 queueing system with fixed times of feedbacks is expended to a generalized situation, i.e., every customer accepts total m times of services and the distribution function of every service time is different from each other. A customer on its ith service is regarded as a classCicustomer. The joint probability generation function of the queue sizes of every class of customers under steady status is presented, and a method to calculate the mean queue sizes of every class of customers is proposed. The results can be widely used in all kinds of communication and computer networks, therefore, a powerful mathematical tool is provided for their performance analysis.
A new signal labeling designed criterion is proposed for bit interleaved coded modulation with iteratively decoding (BICM-ID) when using pseudo interleaver. A new eight phase shift keying (8PSK) signal labeling is designed based on it. Comparative study of different labeling is done through analysis and computer simulation. The results under AWGN show that the new designed signal labeling outperforms the others.
Based on the investigation of adaptive modulation issue for vertical Bell lab layered space time (VBLAST) system in time varying channels, a novel power control algorithm is proposed, which is called average power control. By controlling the transmitting power of adjacent time slots on a whole, the algorithm can improve the power usage by 10 percent, and enhance the performance of the system at about 05?dB at the same time.
The joint estimation (JE) method is proposed to combat inter-carrier interference (ICI) problem in ultrawideband orthogonal frequency division multiplexing (UWBOFDM) system. The JE receiver can estimate the ICI matrix and eliminate the interference by multiply the received signal with the inversion of ICI matrix. Simulation results show that the JE receiver could eliminate the error floor that is brought about by ICI.
A scheme of symbol timing is proposed, which is based on a modified parallel autocorrelation algorithm. By using the iteratively modified received signals as the local template of the match filter, the power losses caused by waveform distortion decreased. At the same time the acquisition convergence will get fast without complex estimation like RAKE. We analyze the effects of timing estimation error on bit error rate in the multipath environment. The simulations showed that the proposed method can find the symbol timing fast and accurately.
In this paper, the quantum field equation of optical soliton is obtained in the lossy fiber by means of heat reservoir theory. The squeezed ratio of the quantum soliton is obtained with the linear approximation. We study the impacts of the initial chirp on the quantum soliton in lossy fiber with numerical method. The numerical results show that the positive chirp can slower the destruction on the squeezed soliton while the negative chirp quicken the destruction.
For the problem of performance degradation of the traditional subspace based user identification detector (UID) in multipath channels, based on the reconstructed signaling sequence matrix that includes the information of multipath channels, a new subspace based UID was proposed. The simulation result shows that the proposed UID will be ensure a low false alarm rate in both the multipath channels and heavy “near far effect” environments.
We compensate the biases of the proposed estimators which estimate the m parameter in Nakagamim fading since they all are not unbiased. We study the performances of these m estimators, with emphasis on the biases and the biases compensation of the estimators based on generalized linear model. We explore numerical linear fitting method to get experimental formula for each. According to our analysis and numerical results using Monte Carlo simulation, the bias is a linear function of m parameter and the number of i.i.d samples used in the estimator whenever the estimator is moment based or maximum likelihood based. Numerical results are presented to demonstrate that the linear compensating formulas work well for all the estimators. In real mobile environment, the fading channel may be time variant or m parameter should be estimated in time, which makes the i.i.d samples used in the estimation of m can’t be very large. In this situation, the compensated versions of m estimators will be useful.
A new pulse shape based on wavelet for ultra-wideband (UWB) system was presented. The sub-nanosecond pulse, which, referred to as monocycle, was defined as wavelet monocycle because it could be made by selecting the translation and dilation factors of wavelet to meet the FCC spectral mask for UWB system. The performance of time hopping pulse position modulation (THPPM) UWB system using this wavelet monocycle was studied under additive white Gaussian noise (AWGN) channel. The simulation results show that the performance of the UWB system using wavelet monocycle is better than that of other conventional UWB system such as using Gaussian monocycle and Scholtzs monocycle.
A new SDRL (scalable decentralized replica location method) in data grid is proposed. In SDRL replica location index nodes and replica location nodes are used to accelerate the process of locating multiple replicas of the same data file. Replica location index information are spread evenly on index nodes which can adapt to the joining or departing of index nodes. Replica location nodes support local query for local replicas. Analysis and experiments show that SDRL can locate the index nodes quickly from the logical file names and gain scalability and good load balance.
According to the modified constant modulus algorithm (MCMA) s cold start ability and decision directed least mean square (DD-LMS) algorithms small residual error property, a dual mode blind equalization algorithm was introduced. With MCMA, the channel eye diagram would be opened and then switched to DD-LMS algorithm to decrease the residual error after convergence. The algorithm could be switched between MCMA and DD-LMS automatically according to the decision rule. Equalization output would be sent directly to the decision device without phase recovery operation so that it can simplify systems design and promote systems efficiency.
The traditional map matching algorithms used in aided inertial navigation system (INS), such as terrain contour matching (TERCOM) and Sandia inertial terrain aided navigation (SITAN) algorithms were investigated of not meeting the requirement of low speed vehicle localization on the reference map. A single step localization algorithm based on map contour was put forward. To ensure its validity and stability, two judgments on miss matching point and switch between INS and map localization were determined in this algorithm. The result of simulation indicates that the positioning accuracy can be determined by the resolution of reference map, also indicates that the circle of equal probability (CEP) is 07 times of the resolution with a middling INS in this algorithm.
The research on the transmission efficiency of data packet in Rayleigh fading channel is presented in the paper where the radio channel is modeled according to the GillbertElliott model. The research shows that the transmission efficiency depends on the packet size and the status of the channel where the packet is transmitted. Based on the founding，the optimal length of data packet during the transmission is deduced. The corresponding simulated is executed to testify the results of analysis. According to the results obtained from analysis and simulation, the dynamic adjustment mechanism on the packet size aimed at different service and channel condition is proposed.
A new algorithm of impulse noise removal is proposed based on the characters of image structure and noise. During noise detection a switching method which have two stages is adopted. The min-max operator is used first. Then further detection is conducted by using the information of structure around the pixel. The pixel is identified between noise and signal by a threshold. If it is a noise point, the value is replaced by rank ordered mean (ROM) of the filter window during noise removal. Compared with other several algorithms, the proposed algorithm can protect details of image efficiently while removing fixed valued impulse noise.
In orthogonal frequency division multiplexing (OFDM) system, the properties of cyclic prefix (CP) energy difference and set correlation are not destroyed at the back of CP in multipath fading channels. Optimum combined with the two merits, a new time synchronization method is proposed in this paper. Simulation results demonstrate that the proposed method has good timing estimation performance over multipath fading channels. And the proposed method is robust to the frequency offset and the performance will be further improved with the increasing of Dopple r frequency shift.
After proposed the concept of distributed mobile terminal and its importance function features, a few aspects about distributed mobile terminal are presented, including the functional model and system architecture, the basic state transition of component and aggregation control procedure. The design and realization of the test bed is introduced.
An on-line accounting management mechanism for IPDiffServ network is presented. By implementing optimized traffic engineer, it can timely back off the congestion as well as keep the price unchanged. It improves the ability of quality of service (QoS) assurance and the ability of congestion recovery, provide better performance with lower cost. Our simulation has verified these merits.
A simple timing and frequency synchronization method for the uplink orthogonal frequency division multiplexing code division multiple access (OFDMCDMA)was proposed, where the multi-user symbol timing was achieved by making use of good correlation property of training sequences that are distinguished not only in frequency domain but in code domain. Also the frequency offset was estimated based on maximum likelihood (ML) principle. Simulation result shows that the mean square error (MSE) performance of the proposed estimation algorithm is satisfied.
PPS (parallel packet switch) can realize high speed switching by using multiple low speed switches. This kind of switch has become a hotspot in high speed switching area. In this paper, we firstly analyzed the current situation of the PPS. Then a new frame based PPS with a new scheduling algorithm was presented. Mathematic analyses showed that this switching architecture can guarantee delay bound and the sequence of the packet.
In this paper a new Bent sequence is constructed by 4 permutation and component wise product for a given new Bent sequences and concatation sequence.The constructed Bent sequences and the original Bent sequences isn’t linearly connected,by which a great number of non-Bent based and non-linear based can also be constructed.
Combining vertical bell laboratories layered space time(VBLAST) and multi code code division multiple access(CDMA) is an effective way to improve data speed, a good communication character can be obtained based on spreading codes with zero correlation window. The capacity formulas are proposed based on the study of the capacity of VBLASTCDMA system under loose synchronization (LS) code and Walsh code respectively under frequency selective and correlative channels. It shows that the capacity of VBLASTCDMA based on LS code is higher than that based on Walsh code.
A mobile IP authentication protocol was proposed in this paper based on identity based cryptography. The protocol accomplishes the mutual authentication and key agreement among entities of mobile IP. It can provide anonymous service that guarantees the confidentiality of the mobile users identity and location information. The security the protocol can fulfill the secure requirement of mobile IP.
An improved adaptive sampling algorithms to improve the efficiency and flexibility of network load measurement is proposed after the detailed research on the theory of adaptive control and traffic characteristics. Performance comparison ,shows that there is improvement by 40% on the measurement precision. It can also provide several visual outputs with different granularity to support the measurement efficiency and flexibility. So the improved algorithm suits for the environments of measuring highspeed network load with high burst arrival rate.
Compared to the characteristic of ultra-wideband (UWB) signal and multi-path propagation within indoor environment, a low complexity RAKE receiver scheme was expatiated, which debases system sample rate. Moreover, an algorithm based on minimum mean square error (MMSE) parameter estimation was proposed as well to reduce the finger number and to improve performance. The performance of simulation receiver bit error rate (BER) shows that the algorithm is adaptive to pulse based UWB system when narrowband interference and inter symbol interference (ISI) exist.
The control system of brushless direct current motor based on DSP （digital signal processor） is proposed in the paper. The relevant hardware is given. A design scheme of software is showed. The experiment result shows that the hardware based on TMS320LF2407A can meet the requirement of a real time control system. It is very convenient to use in any advanced control strategy. The design is simple, reliable and easy to be applied.
Based on ElGamal digital signature and zero knowledge, a practical two way user authentication scheme was presented. It was obtained that reliability and availability of request information could be improved through random number and online challenge response interactive system. Meantime, the problem about key distribution and storage related to user authentication scheme was solved securely and effectively by using smart card, and highly security of user information was acquired accordingly as well. As a conclusion, the securities of the proposed scheme under the assumption about the difficulty of computing discrete logarithm are analyzed.
Based on the empirical envelope of a compressed video stream, a traffic description model was developed. With aid of the model, the data rate and burst features could be denoted by all of the tangent points of the empirical envelope. To make the model more practical in use, an algorithm was proposed to remove the redundancy within the description results. Since the empirical envelope was the only tightest envelope, the traffic features of a compressed video stream could be described completely and uniquely. The drawbacks of the traffic description models used in nowadays network resource management could be resolved with the proposed model. It is also showed how the proposed model can be applied to determine the optimal bandwidth to be reserved when requesting the guaranteed service via RSVP（resource reservation protocol）.
Although the transport bridge proposed by international standardization organization development environment (ISODE) is a workable solution which interconnects the open system interconnection (OSI) hosts with the transmission control protocol/Internet protocol (TCP/IP) hosts, it requires that the transport application protocol interface (API) in the TCP hosts should be rewritten. A new transport gateway approach with better portability is proposed which implements the protocol translation function between TCP and transport protocol 4 (TP4). Furthermore, a novel adaptive congestion control algorithm is designed in the gateway which smoothes the rate difference between TCP and TP4 automatically through adjusting the flow control window dynamically. The test in the aeronautical telecommunication network (ATN) validates that the gateway achieves good performance with quality of service (QoS) guaranteed.