Applied Mechanics and Materials Vol. 443

Abstract: In this paper, we proposed a new symbol rate estimation algorithm for phase shift keying (PSK) and qua drawtube amplitude modulation (QAM) signals in AWGN channel First we constructe a delay-multiplied signal, from which we obtaine the modulated information. Then we calculated the instantaneous autocorrelation of the delay-multiplied signal to pick out the phase jump. To eliminate the restriction of frequency resolution in fast Fourier transform, we performed a Chirp-Z transform to find out the exact spectral line which represente the symbol rate of the signal to be analyzed. Compared with the existing algorithms, it is a simple solution that has a better performance and accuracy in low signal-to-noise-ratio channel conditions. Simulation results show that the probability of relative estimating deviation below 0.1% reaches 100% and the average and standard variance of absolute estimation deviation are at the magnitude of 10^-2 when SNR is over 2dB.

Abstract: To study this issue, a new structure for UWB communication systems based on compressed sensing (CS) is proposed. This proposals focus on solving two main problems. First, building a system based on the CS to reduce the sampling rate at the receiver. Second, analyzing the impact of inter multi-pulses interference (IMI) to the ability to transmit high data rate of UWB communication systems. Experimental results show that, the IMI will be changed greatly depending on the different types of channel model. In the LOS channel model, the effects of the IMI negligible thus data transmission rate can be achieved up to several hundred Mbps. whereas for the NLOS channel models, the effects of the IMI large so data transmission rate can only reach a few Mbps.

Abstract: With the rapid development of the number of mobile phone users has accumulated a large number of graph data, graph data mining has gradually become a hot area of research. Traditional data such as clustering, classification, frequent pattern mining gradually extended to the field of graph data mining research. Introduced at this stage graph data mining technology research progress, summarizes the characteristics of the graphical data mining, practical significance, the main problem, and scenarios to discuss and forecast chart data, especially research on uncertain graph data become trends and hot spots.

Abstract: In this paper, we have proposed the Energy Efficient Localization of Primary Users for Avoiding Interference in Cognitive Networks. This approach can be implemented in networks where GPS like localization techniques are not available. Our algorithm locates the PU based on leveling and sectoring approach and then disable region is identified to avoid interference to the primary user.

Abstract: Following the deployment of network multimedia applications, such as video conference, simulation research on video stream characteristic is more and more important. MPEG standard encodes the video sequences to frame I, P, and B, and has higher compression rate and bandwidth saving character. MPEG video traffic characteristic and simulation methods are researched in this paper. Network simulation version 2(NS-2) kernels is extended using C/C++ programming language. An MPEG video traffic generator modules and simulation interfaces are designed in NS-2 kernel. Simulation results show that the proposed extension method is feasible and effective.

Abstract: In this paper, we investigated the low density parity check (LDPC) coded performances of slow-frequency-hopped binary phase shift-keying (SFH/BPSK) systems in the presence partial-band interference (PBI). The contributions of this paper are two folds. First, we give the bits error probability (BER) of the SFH/BPSK system with PBI by analysis, and further verify it by numerical results. Second, we investigated the effects of code rate, code length, the number of symbols per hop (SPH) and interleaver on the performance of the SFH/BPSK system with PBI by numerical simulation.

Abstract: This essay describes a new radio encryption technique among communication equipments, that is embed confidential information in normal carrier by using digital watermarking to achieve the purpose of protecting confidential information and confusing illegal interceptors. Meanwhile it also gives embed watermarking based on integration and Detection Algorithm.

Abstract: In this paper, we propose to apply a centre scheduling algorithm in the CRAHNs with a cluster. In this network, the cluster head assigns time slots to each node so that every node can be fair to transfer data. The scheme schedules the links to the same destination node first, which has the largest topology structure, then another destination node whose topology structure is larger than the rest. The algorithm presented in this paper considers both the fairness and the spatial reuse, and the simulation results show that this algorithm still has a good performance when the topology is so large.

Abstract: Using the TIGER database to create a realistic road map and establishing car following model and lane change model for simulation scene in SUMO. It evaluates the performance of the routing protocols including GPSR, ADOV and DSDR in this scene, and then analyzes their merits and drawbacks in Vehicular Ad-hoc Networks (VANETs) by the simulation of NS2. The results of the analysis show that the GPSR have the best performance in the three kinds of routing protocols. It proved that the protocols based on location information are more appropriate to VANETs. However, it is difficult to meet the needs in the VANET communication in urban scene, so the protocol needs to improve.

Abstract: In a wireless mesh network, the need for cooperation among wireless nodes to relay each others packets exposes the network to a wide range of security threats. A particularly devastating type of threats is the so-called wormhole attacks. In order to defense against the attack, a type of wormhole attack model and a watch nodes-based wormhole attack detection scheme were presented in this paper. The scheme that is based on the combination of a number of techniques, such as distributed voting, watch nodes based detection and identity-based cryptosystem. Qualitative analysis and simulation show that the wormhole attack detection scheme is more advantageous over the some of the previous schemes in terms of performance and cost.