Applied Mechanics and Materials Vols. 385-386

Abstract: In this paper, we propose the modified minsum decoding algorithm of LDPC(Low-Density Parity-Check) code in the simplified difference-domain on the basis of detailed analysis of LDPC decoding algorithm in difference-domain. The simulation indicates that the proposed decoding algorithm offers almost no performance degradation compared with the BP(Belief Propagation) decoding algorithm in log-domain and the decoding algorithm in difference-domain and offers better performance than minsum decoding algorithm in log-domain and greatly reduces the computation complexity in AWGN(Additive White Gaussian Noise) channel and under BPSK(Binary Phase Shift Keying) modulation.

Abstract: Underwater conduction current field communication is a low noise system. It is absolutely to realize the short-distance underwater wireless communication .Compared with underwater acoustic communication, because of the electrical noise underwater is very low, so using underwater current field to realize short-distance underwater wireless communication has a certain advantage. In order to implement the design of conduction current field in underwater communication system better, its necessary to explore and study underwater signal transmission by establishing mathematical model of underwater signal propagation characteristics based on the theory of constant current field and simulating the mathematical model with MATLAB. To fully understand the underwater conduction current field channel characteristics in the actual field environment, we established a simulation model of underwater conduction current field communication channel physical experiment and obtained the amplitude frequency characteristics of the channel based on the external field test data, it laid a solid foundation for the parameter selection of underwater communication system.

Abstract: In mobile satellite communication based on OFDM technology, the system performance can’t be optimal if the cyclic prefix (CP) length and subcarrier interval of LTE specification are transplanted into mobile satellite communication directly. In this paper, we analyze the impact of inter symbol interference (ISI) and inter carrier interference (ICI) which are caused by multipath delay spread and Doppler frequency shift separately on system capacity, and derive the optimal CP length and subcarrier interval for GEO, MEO and LEO mobile satellite communication by numeric calculation. Finally, the simulation results show that the OFDM parameters of LTE specification can be used in GEO mobile satellite communications, but cannot in MEO and LEO.

Abstract: With the popularity of group-oriented applications, secure electronic communication among all group members has become a major issue. This paper proposes a distributed group-oriented key management scheme for secure electronic communication. The scheme deploys Elliptic Curve Diffie-Hellman (ECDH) which is more lightweight as compared to regular Diffie-Hellman. According to the security analysis, the proposed scheme provides a number of desirable security properties, including group key secrecy, forward secrecy and backward secrecy.

Abstract: In optical networks, erbium-doped fiber amplifiers (EDFAs) are used to provide a wide and flat gain spectrum. Amplified Spontaneous Emission (ASE) emitted from EDFA adds to signal and grows rapidly. This accumulated ASE noise may limit the effective amplification due to saturation effect and affects the receivers bit error ratio (BER). In this paper, we show the impact of ASE noise in transmission fiber by using three different modulation formats: 33%DPSK, 66%DPSK and DPSK. In recent years, optical fiber communication system began to use the DPSK (Differential Phase Shift Keying) format to replace the traditional OOK format, which has been intensively investigated in numerical and experimental works.

Abstract: A set of fixed-phone cluster management system was designed based on C&C08 program control unit and next generation network (NGN). C&C08 is responsible for the bottom access and transfer of the fixed-phone calls. Applying the computer telephony integration (CTI) technology we can realize the telephone call management through a computer. Using this system, fixed telephone managers can conduct limitation control for cluster management users information and implement list query of cost easily, so that managers can know the detail cost. In addition, based on the present situation of the telecom business, we designed four telecommunication services for enterprises and institutions, and added them to the fixed-phone cluster management system. For the cluster management users, they can subscribe to those services according to their needs.

Abstract: In order to provide higher available bandwidth, flexible accessing and shared multimedia resource to the application in Media oriented systems transport (MOST) network. This paper proposed an implementation strategy of MOST network management, which is described by finite state mechanism model, discussed the scheme of multiple synchronous audio or video channel connection (SA/VCC) management. These works give an improved solution for MOST, which supports flexible accessing and reliable data transmission for multimedia devices, provides reasonable bandwidth allocation and shared multimedia resource in synchronous channel in practical.

Abstract: Both underlay spectrum sharing radios and overlay spectrum sharing radios have their advantages and disadvantages. Ultra wide band (UWB) and cognitive radio (CR) are important underlay and overlay technology respectively used as secondary radio systems. In this paper, a cognitive impulse ultra wide band (CIUWB) spectrum sharing radio technology is presented based on impulse UWB and CR.

Abstract: Existing schemes have been firstly analyzed for secure routing protocol in Ad hoc networks. Then we present a new scheme for secure routing protocol base on AODV. Security features in the routing protocol include threshold authentication mechanism based on elliptic curve cryptosystem algorithm and improved the process of authentication without relying on the availability of a certificate authority center. Furthermore, the neighbor supervising mechanism combining with reputation mechanism are adopted to strengthen the management and supervision to network nodes, make the whole process of routing protocol under administration and supervision.

Abstract: A semi-supervised local subspace alignment (SSLSA) algorithm for wireless sensor networks localization is presented. SSLSA method has the following features: 1) only using pair-wise distance between each node and its neighbors within a certain communication range, 2) aligning subspaces with the constraints of anchor nodes thus avoiding the accumulation of error, and 3) obtaining absolute positions of all sensor nodes directly without any other transformation process. The localization performance of this method is compared to the MDS-MAP(P, R) and LSA methods.