Applied Mechanics and Materials Vol. 610

Abstract: The coverage and capacity of high speed data service in coal mine hot spots is not sufficient in present TD-SCDMA communication system. This paper proposes a TD-SCDMA & Wi-Fi network interworking solution , utilizing the high speed data transport of Wi-Fi network on the foundation of TD-SCDMA system. The results show that the solution is feasible and effective .

Abstract: In this letter, we derive the analytical expressions of the degree distributions for a kind of networks model random initializing attractiveness and preferential linking, which analyzed degree evolution by using the master equation approach. We also discuss the theoretical justification of the scale-free behavior about the proposed model. The influencing range of initialization to the degree distribution only related to initialization’s expectation under the global meaning. Finally, a series of theoretical analysis and numerical simulations to the scale-free network model are conducted in this letter. The results of computer simulation is presented to the theoretical analysis.

Abstract: The statistical properties of relay channel are quite different from the direct transmission channel for including two phases channel of source to relay and relay to destination. In this paper, we study the relay channel from three viewpoints of probability density function (PDF), level crossing rate (LCR) and Doppler spectrum for Rayleigh, Rice and Nakagami fading models. The closed form expressions are deduced, and simulation evaluation is done to verify the results.

Abstract: The phase spectrum time delay estimation (TDE) method is being used widely in trajectory tracking and target location, which due to its superiority in computation load and accuracy. However, the precision of TDE had declined severely as the result of noise. This paper plans to analyze the factor of noise, which has effects on the performance of phase spectrum TDE algorithm based on the difference principle. Theoretical analysis and computer simulation show that the fluctuation of phase caused by noise leads to poor performance. Furthermore, the extent of the influence relates to the time delay and signal frequency.

Abstract: The guard interval (GI) filling with cyclic prefix (CP) is inserted in the conventional orthogonal frequency division multiplexing (OFDM) system in order to be free of the inter-symbol interference (ISI). The frequency spectrum leakage out of band is mitigated by using the time-domain windowing method. Meanwhile, the GI-free OFDM have been studied in order to achieve high efficiency of bandwidth usage. This paper addresses the windowing method of partial response function for this case. It is shown that the information data can be detected precisely and the frequency spectrum leakage is mitigated without loss of bandwidth efficiency.

Abstract: A smart antenna using 4x4 Butler matrix for 5.8 GHz band is designed. The antenna array has four inputs and is excited by the Butler matrix feeding network to electronically steer the beams in desired directions. The architecture of the Butler matrix beamforming network is designed without using cross couplers, in fact the array antenna will be surrounded by the hybrid couplers, and it leads to decrease losses due to the crossing lines. The designed prototype is simulated on Rogers RT /duroid 5880 substrate with a relative permittivity of 2.2 using ADS momentum software.

Abstract: Because of the DV-HOP algorithm in wireless sensor network (WSN), the first jump range error, which affect the positioning error of the whole node network problems. This paper puts forward an improved algorithm is proposed. The algorithm is mainly using the RSSI ranging technology, in the process of DV-HOP first jump range through correction of RSSI ranging technology, to reduce the distance measuring error, in order to improve positioning accuracy. The simulation results show that compared with traditional DV-HOP algorithm. The improved algorithm can without additional hardware and computation under the premise of improving positioning accuracy.

Abstract: From the point of view to improve QoS of Ad Hoc network, this paper analyses the problem about mobile nodes in Ad Hoc network and decides to solve the problem by designing effective MAC protocol. Therefore, a novel random multi-access protocol using Binary Tree Collision Resolution for collision packets in Probability-Persistent Random Multi-Access (IBTCRPP-CSMA) is proposed. The throughput of IBTCRPP-CSMA and computer simulation experiments are obtained. Simulation results agree with theoretical analysis. By contrasts of throughputs among several CSMA protocols, IBTCRPP-CSMA has higher throughput and channel utilization, thereby ensuring the system’s high QoS.

Abstract: This paper presents a new wireless sensor network MAC protocol: the probability detection CSMA protocol with monitoring function based on the improved binary tree conflict resolution algorithm. By using the average cycle method, the paper gets the mathematical expressions of the throughput, system average delay of the probability detection CSMA protocol with monitoring function and the probability detection CSMA protocol with monitoring function based on the improved binary tree conflict resolution algorithm through complicated mathematical modeling, rigorous mathematical derivation. The computer simulation results not only confirm the correctness of the theoretical analysis but also show that the probability detection CSMA protocol with monitoring function based on the improved binary tree conflict resolution algorithm due to adding to the conflict resolution algorithm, resulting in the increases of systemic throughput but increase the time delay of the system.

Abstract: The capture of long Pseudo-Code code is the most important technology in spread spectrum system. we use XFAST,AVERAGE to solve this problem in old days. A new algorithm is proposed which based on the time domain samples and binary search according the autocorrelation of the Pseudo-Code (PN code) and improve the speed of the capture of long Pseudo-Code code in spread spectrum system. Firstly, received spread spectrum signal's simple rate is reduced to a quarter of the chip rate and determine with a specific method, then divide the local PN code into four parts and accumulated to a new sequence. finally, the synchronous pseudo-code is captured with the correlation of the two new reference sequences. Compared with conventional methods such as XFAST, capture time and precision are improved.