Applied Mechanics and Materials Vols. 198-199

Abstract: This paper presents the application of the hyperbolic frequency modulated (HFM) signal to acoustic propagation in order to improve the performance of underwater acoustic (UWA) communications. Due to the large delay spread caused by multipath propagation and the severe Doppler Effect of the channel, we propose the using of double HFM signals as preambles for Doppler estimation, frame synchronization in UWA communications. A theoretical analysis about Doppler-invariability of HFM signals was provided firstly, then some numerical simulations about Doppler estimation were implemented, and experiments on testing performance of double-HFM preambles for frame synchronization in the pool were carried out as well. The simulation and experimental results show that using double-HFM signals as preambles has the capability to take an explicit Doppler estimation and retiming for frame synchronization, demonstrating that it has a good prospect in underwater acoustic communication system, especially for moving platforms.

Abstract: In order to enhances the battle efficiency and transport support ability, accomplish the central task of “perform duties, counterterrorism, handle thunderbolt”, it has a very important significance to strengthen the safety administration of vehicle and prevent traffic accident. the paper from a safety administration point of view, set up a transport safety ensuring effectiveness evaluation indices system for the Armed Police Force(APF),and calculated the weight of the indices using AHP method. Finally, Based on the theories of Fuzzy comprehensive evaluation theory, the comprehensive evaluation model on transport safety ensuring effectiveness of APF is established.

Abstract: As a typical network industry, the inherent characteristic in technology and economy of telecommunication determine that its effective competition requires equal interconnection. This article analyzes the principle and network economy characteristics of telecommunication network interconnection, expecting provides the basis for promoting rapid and healthy development of the telecommunications industry.

Abstract: According to the characteristics of data access in Internet of things, we put forward a replicate distribution method of minimum cost which considers the number and type of replicate in cloud storage. By this method, the replicates will be distributed to storage servers with minimum total cost from several data service points. This method is fundamental research of low cost distribution for replicates in cloud storage based on data access load.

Abstract: Monitoring system design of mine gas Monitoring System were designed according to the traditional lacked of the real-time and early warning functions and so on problems. A multi-hop sensor network based on TinyOS is designed. The system is based on hierarchical network architecture. The software design principle based on TinyOS is introduced, which can realize the multi-hop communication. A simple Ant colony algorithm is designed in this sensor network to improve the network lifetime. According to simulation results and Test Research, this system can efficiently realize the multi-hop data communication and reliable.

Abstract: The past few years have witnessed increasing focus on the potential applications of wireless sensor networks. Sensors in these networks are expected to be remotely dispersed in large number and to operate autonomously and unattended. Clustering is a widely used technique that can enhance scalability and decrease energy consumption over sensor networks. We present an energy-efficient distributed multi-hop clustering approach for sensor networks, which combined multi-hop transmission with clustering method, aiming to balance the energy dissipation and prolong the whole network lifetime. Simulations showed that the protocol proposed worked nearly 100% more efficient compared with LEACH and HEED.

Abstract: Possessing a shrewd accurate time synchronous mechanism is the prerequisite of many network applications. This paper puts forward a kind of time synchronous method for LAN(local area network) based on general PC, replaces systematic clock with TSC(time stamp counter) register as synchronous time source, achieves synchronization through a client and server style, it is easy to calculate and needs less expense. The result of experiment shows that the synchronous precision of this method is higher, and can be kept longer; it also shows that this method is suitable for the application occasion which requires higher time-synchronization.

Abstract: Within the past few years, a great deal of attention has been drawn towards the CDMA system. The state of a CDMA system has two cases: saturation and instauration. After the system is saturated, no more users are allowed to access to CDMA systems with traditional method. In order to enhance the maximum number of users and the all users’ satisfaction while guaranteeing users’ quality of service (QoS) –SINR (signal-to-interference–plus-noise) requirement, this paper presents a degradation scheme based on user satisfaction in CDMA systems. Simulation results show that the proposed scheme can be allowed more users to access to and increase the total users’ satisfaction, leading to higher system capacity and resource utilization.

Abstract: Aiming at the satellite mobile communication, the cooperative communication technology is applied to the forward downlink in this paper, and one scheme with two satellites based on the coded cooperative which used the Alamouti space time block code is presented. Simulation results show the coded cooperative strategy can obtain better performance than the traditional uncoded systems, which is lower than the MIMO system with two transmit antennas and one receive antenna based on the Alamouti code, but the power of the terminal was decreased. It has the advantage in communication range and low complex mobile terminal, which has a certain application prospects in satellite mobile communications in the future.

Abstract: As the development of the society and economy, more and more cars are used in the people life. Parking the car in a busy mall is often frustrated for us due to lack of the parking spaces. The problems mainly consist of two aspects. First, when we go to the destination, we do not know where the parking lot is and how many parking spaces is free. We have to spend a lot of time to find a parking lot. Besides, the parking lot usually is great, it is difficult for us to find the free space efficiently. Traditional solutions are implemented based on the TCP/IP networks or sensor network. TCP/IP solutions often require a lot on the infrastructure. Solutions with sensor network can not navigate the driver precisely. In this paper, we propose a novel parking management system with RFID and sensor networks, which can not only detect and locate the free parking space quickly, but also navigate the car to the parking space effectively. Our experiment shows that the proposed system is desirable for us to use in the life.