Applied Mechanics and Materials Vols. 263-266

Abstract: A novel equalization approach for rapidly time-varying channels of OFDM systems is presented,which we propose receiver windowing based ‘subblockwise’ tracking scheme to combat with intercarrier interference (ICI),whose aim is to force each subblock of one OFDM block as time-invariant such that channel equalization can be performed by a time-invariant structure. Meanwhile, signal-to-interference ratio (SIR) is numerically evaluated and derived as a close-form expression for performance analysis. Simulation results show that the proposed scheme outperforms the existing equalizers, while requiring a lower complexity.

Abstract: Reliability is one of the key issues in widely application of real-time video transmission. The fault-tolerant mechanisms of 1394b optical bus protocol are investigated for 1394b optical bus-based real-time video. In addition, a method of hardware redundancy fault-tolerant is proposed. The hardware topology is built with embedded video function nodes, and fault-tolerant control software is realized on VC platform. Furthermore, the 1394b optical bus-based video transmission is demonstrated by experiment, due to which, performances of fault-tolerant for the transmission is evaluated.

Abstract: The traditional constant modulus algorithm (CMA) has the disadvantage of slow convergence in blind equalization algorithm. This paper studied one improved algorithm based on momentum factor constant modulus algorithm(MCMA) to solve this problem, momentum factor was added to the weight vector iteration formula of CMA to improve the convergence speed. theoretical analysis and simulation showed that: in the case of the same equalization effect, the MCMA converges faster than the traditional constant modulus algorithm, and also different momentum factors have different convergence effects. The larger the momentum factor , the better convergence effect in the defined domain of the momentum factor.

Abstract: When several ultra-wide band (UWB) communication systems coexist, multiuser interferences (MUI) are unavoidable. To cope with the MUI of UWB systems, the independent of UWB signals are investigated and a novel receiving method is proposed. At first several antennas are utilized to receive the transmitted signals of different UWB users, and the mixture signals are gained. Then the mixed signals are separated by independent component analysis algorithm to recover the transmitted signals of each UWB users. Finally, the information of each UWB users transmitted is demodulated. Computer simulations show that the proposed method can efficiently resist the interference of different UWB users.

Abstract: Due to strong coupling among multi-channels of phase-only sampled gratings, the effects of manufacturing errors on sampled grating are different from fiber gratings with a single reflection peak. The influence was investigated by numerical simulation. When group delay and reflectivity ripples are caused by random phase and amplitude errors, inside a grating channel, the ripple amplitude at short wavelength is larger than the one at long wavelength, and this phenomenon was qualitatively explained using the principle that the reflecting position varies with the wavelength of incident light in a chirp grating. The sub-grating length of the transfer matrix method, which is decided by the accuracy of phase mask and UV writing, exerts an influence on the ripple amplitude. For multi-channel fiber gratings, stitch error impairs the periodicity of sampling function, so this kind of fabrication error leads to unequal performance reduction in different channels, and the reduction is more serious for channels at two sides.

Abstract: Now 3G mobile technologies is the research focus in the field of mobile communication. Streaming media technology based on 3G networks is always difficult problems in this field. P2P streaming media technology has become the mainstream application form of internet. In this paper, we design a P2P streaming media cache allocation algorithm based on 3G networks. This algorithm use network protocols to connect 3G network with P2P network to minimize transmission delay and to improve the transmission efficiency. Simulation experiments show that this algorithm presented in this paper has the obvious performance advantage in transmission delay and transmission efficiency.

Abstract: Head of Line (HOL) blocking and deaf node problem are the main challenges in the smart antenna system in wireless ad hoc networks. To resolve these difficulties, we propose a novel packet scheduling algorithm based on the Directional Network Allocation Vector (DNAV). In the new algorithm, we divide the surrounding space of a tagged node into interference regions and free regions, and then transmit packets selected in turn from the data queue if there is an appropriately free region. The proposed algorithm can eliminate the deaf node problem and resolve the HOL blocking efficiently. Higher throughput and lower network delay are obtained by adapting to the dynamic network topology than other methods. The simulation results confirm the validity of the proposed algorithm.

Abstract: A coherent DPSK transmission system is presented to improve the receiver sensitivity for free space optical (FSO) communication. The coherent DPSK is an effective way to overcome the atmospheric turbulence. The eye diagram and bit error rate (BER) of the system are got by the simulation. Results show that with the coherent reception method, coherent DPSK offers improved signal-to-noise ratio (SNR) performance compared to the DPSK without coherent and OOK format. And hence it can be effective to overcome the signal impairment caused by atmospheric turbulence. It is shown that the sensitivity of the system employing coherent DPSK is 3dB better than a comparable system using DPSK without coherent and 9dB better than a system using OOK.

Abstract: The anonymity and dynamic characters of P2P network make it become hotbed with selfish and malicious behaviors. To improve the wholly quality and security of the network, this paper gives a new distributed trust model to evaluate the trust values of peers which introduces the concept of interaction satisfaction and concerns on both direct and indirect trust. The experiment data shows that this trust model can distinguish good peers and make them have the high ratio of successful interactions.

Abstract: This paper first introduced the related protocol of MANET and mobile IP technology, and then presented the research and implementation of AODV protocol of the dynamic gateway based on the MANET and Internet interconnection, including AODV dynamic gateway, system architecture of dynamic gateway, reform of the AODV protocol, gateway switch and load balance. Finally, it introduced the test environment of the system, and verified through NS2 simulation that the load of the network could be reduced by the improved AODV protocol.