Applied Mechanics and Materials Vols. 321-324

Abstract: On the basis of interference model, the article puts forward a self-adapting routing strategy of Wireless Mesh Network, which can significantly improve the efficiency of the routing by choosing a minimum interference path. Due to regularly-distributed self-adapting adjustment and load balance, the routing can adapt to the dynamic network environment. The simulation shows that IBAR can significantly improve the throughput performance compared with the traditional AODV and HWMP protocols.

Abstract: Any carrier frequency offset will cause a loss of subcarrier orthogonality which results in ICI and hence performance degrades severely in MIMO-OFDM systems. In this paper, a time and frequency synchronization solution for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed. The synchronization is achieved using one Constant Amplitude Zero Auto Correlation (CAZAC) sequence-based preamble which is simultaneously transmitted from all transmit antennas in the same OFDM time instant. The synchronization is accomplished sequentially by coarse time synchronization, fractional frequency offset estimation, integral frequency offset estimation and fine time synchronization. The simulation shows that the proposed algorithm can estimate the timing and frequency offsets efficiently in MIMO-OFDM systems, especially in low signal-to-noise ratio condition.

Abstract: Much of the work on routing algorithms, particularly for multicast, which has been done in the past has used fairly simple models to generate the topological graph which represents the hosts in the network. Good models of the topological structure of a network are essential for developing and analyzing wireless network technology. This paper proposes a more realistic model based on the theory of complex network, incorporating hierarchy and redundancy, and is developed into a network generation algorithm.

Abstract: In this paper, we propose a new improved MC-CDMA system which combines spreading codes from Quasi-Orthogonal Matrix with Orthogonal Complex Wavelet Division Multiplexing (OCWDM). The system is implemented by complex wavelet filters which are able to lower computational complexity and increase flexibility. Novel spreading codes from Quasi-Orthogonal Matrix can be expanded randomly. It can increase user number hugely in system. Improved MC-CDMA named OCWDM-CDMA has much higher frequency spectrum efficiency and high data rate than conventional MC-CDMA. The system also has better BER performance in Gaussian channel than conventional system for much more users.

Abstract: Tag collision happens when multiple tags are energized simultaneously, reflect their respective signals back to the reader at the same time, and the reader is unable to differentiate these signals. This problem causes decrease of the RFID efficiency especially in the tag-intensive RFID system. The dynamic frame slotted aloha (DFSA) algorithm is the most appropriate solution for this problem, which is based on an accurate tags number estimate method. A novel forward predicting and backward verifying adaptive precise tags number estimation algorithm is proposed in this paper. Experiment results show that it is more effective than others.

Abstract: Competition from all walks of life is more and more intense. So WLAN obtains a wide application. However, the main disadvantages of WLAN, coverage scope, movement speed and capacity of communication, are still unavoidable problems. Ad hoc is a good compensation for the main disadvantages of WLAN with its main advantages such as good extensibility, fast movement speed, great capacity of communication, etc. In this paper, WLAN and Ad hoc are introduced in detail, and then integrated according to their respective character. Finally, some main advantages of integration of WLAN and Ad hoc are listed.

Abstract: Vehicle information system is the data center of vehicle communication networks, for the sake of connecting the IPv6 host through IPv4 network area, a virtual network device (VND) in Linux embedded System is designed and implemented as a mid-layer module between the real device driver and internet protocol stack. The VND can establish a virtual tunnel between the vehicle information device and agent server. Both vehicle information device and agent server can support IPv4 and IPv6.Through the virtual tunnel, the agent server picked up the IPv6 packet which was built in IPv4 UDP data area, and transmit the IPv6 packets to the IPv6 remote server. So it works like a VPN device. The hardware platform of the vehicle gateway is based on ARM9, and the software is based on ARM-Linux. The instruction of hardware and software are as well as put forward.

Abstract: Based on the principle of the modulation and demodulation of Binary Phase Shift Keying(2PSK),a mathematical model for the modulation and demodulation of the 2PSK was built and the carrier signal was designed using the technology of Direct Digital Synthesis (DDS).Then,a model to simulate the hardware circuit of the modulation and demodulation of 2PSK was built,and then analyzed in Matlab and Modelsim.Simulation results show that the model not only properly realizes the function of 2PSK modulator-demodulator,but it also simplifies the hardware circuit and reduces the programming time.

Abstract: Internet of Things (IOT) model used in the field of digital publishing is studied, which can protect the security of the digital publication and enhance the layout of China's cultural industry and is also the development trend for digital publishing industry. Comparison from RFID tag, digital publication tag based on IOT model has more advantages in position, visibility, environmental impact and cost etc.. Application issues in the digital publishing field are analyzed and suggestions are discussed from technology to standard, which includes security of digital rights, system construction of digital publishing standards and industry research of watermark technology.

Abstract: With the development of computer technology, people are no longer satisfied with a single operating system. More and more people like to use UNIX system because of its high reliability, good open, and powerful network features. The design of this telecommunications billing system is based on Browser / Server model using the java language for the UNIX platforms laboratory environment. The system can accurately time and automatically charge according to the business types when the user rents the server, and to complete information management of the server and user. This system is simple, friendly interface. It reduces operating costs of the telecommunications operators and improves productivity of them.