Applied Mechanics and Materials Vols. 568-570

Abstract: In the field of digital circuit testability design,IEEE 1149.1 standard focuses on System ON board (SOB) test,while the IEEE 1500 standard is for embedded cores test on chip.Although there is a clear definition of two standards, they have a certain relevance.This article will from the process, test principle, test architecture and related test language to analyzethese two standards, concluding that the differences and similarities .Finally, some problems will be pointed out when use the two standards and then make a prospect on the development of the standards.

Abstract: Rail transportation experimental system is the urgent need of modern railway signal professional colleges and universities teaching equipment. This equipment can deepen students' understanding of theoretical knowledge and improve their ability of practical operation. In this article the design schemes of track circuit for high-frequency test system are simulated. Through the result of simulation the design meet the functional requirement.

Abstract: To acquire channel state information for Massive MIMO system , a downlink beamforming pilots scheme is proposed for efficient channel estimation. The channel estimation overhead of the proposed scheme is independent on the BS antenna numbers, and is only proportional to user numbers. MMSE precoding method is derived to implement the proposed scheme. Finally in simulation the proposed algorithm is compared with conventional algorithms without beaforming training in spectral efficiency performance. The simulation results show that the proposed scheme performs better than the existing schemes.

Abstract: The Ka band for satellite communications is allocated from 27GHz to 40GHz and it is possible to realize the high speed data transmission in this 13GHz bandwidth. However, the attenuation especially the rain attenuation is tremendous for the Ka band. And we need to reserve about 4~8dB link budget to guarantee the typical link reliability 99.9% for the constant coding and modulation (CCM). In this paper, we propose a adaptive coding and modulation (ACM) algorithm that can dynamically change the modulation and code efficiency according to link condition. Based on this algorithm we only need reserve about 1dB to realize the 99.7% reliability. The simulation results show that we can derive more than triple throughout compare to CCM.

Abstract: Channel assignment strategy is a key factor for building a robust and high performance wireless Mesh network. A new channel assignment algorithm called TriCA which considers data traffic interference is proposed, the model is constructed and the idea, computing method and program process are discussed deeply. The simulation result shows that TriCA algorithm can minimize the link interference effectively, and its performance is better than popular MesTic algorithm due to the property of fast convergence and the method of linearization.

Abstract: Based on the traditional DSR Protocol has obvious drawbacks such as short network lifetime in the small reconnaissance UAV ad hoc network, a routing protocols called UEDSR(UAV Energy Dynamic Source Routing Protocol) suitable for small reconnaissance UAV ad hoc network is proposed. This protocol introduces the energy balancing mechanism into the algorithms based on DSR, then improves the situation of excessive energy consumption of hot nodes and prolongs the network lifetime. The simulation of protocol by NS2 illustrates that comparing to DSR the UEDSR protocol achieves about 7% increase in the network lifetime and the packet delivery and the average of network throughput are effectively improved.

Abstract: The computational precoding complexity increases with its dimensions in massive multiple-input multiple-output system. A precoding scheme based on the truncated polynomial expansion is proposed, the hardware implementation is described for the superiority of the algorithm compared with the conventional regularized zero forcing precoding. Finally, under different channel conditions, the simulation results show that the average achievable rate will increase infinitely approaches the regularized zero forcing precoding simulation in a certain order, the polynomial order does not need to scale with the system dimensions.

Abstract: Inspired by the overlap communication theory, a new onshore radio positioning system which superimposed on terrestrial digital transmission system is proposed in this paper. This system overlaps but not affects existing terrestrial digital broadcasting.At the receiver, a reconstruction/cancellation algorithm.is implied to capture the navigation signal and positioning measurements precisely.This paper focus on the construction of overlap system,spreading navigation signal and the capture of positioning measurements.We give a method to generate spreading navigation signal and overlap with terrestrial digital transmission system.The method can reduce the performance degradation due to pilot interference. We also proposes a reconstruction/cancellation algorithm which can solution the capture performance deterioration caused by overlapped system . The simulation results show that this system proposed in this paper can be used in terrestrial digital transmission system and provide good positional function.

Abstract: An arrayed waveguide grating (AWG) multiplexer with flat spectral response has been designed and fabricated by using FPE polymer materials. Experimental results show that the central wavelength is 1550.86 nm, and 3-dB bandwidth is about 0.478 nm, insertion loss is 10.5 dB. Simulated results show that fabrication processing result in the shift of the transmission spectrum compared with the device theoretically designed. Furthermore, the transmission characteristics are discussed, and some efficient ways are reported.

Abstract: Laser Diode (LD) tester is widely used in the research, manufacturing and testing of laser diode, but no verification regulation or calibration specification for laser diode tester has been released until now. With the fully using of the standard instruments in our optical communication laboratory, and referring to the operational manual, specification and relevant calibration regulations, we provide approaches to the calibration of the laser diode tester. The evaluation processes and results of measurement uncertainty for optical power measurement, output DC current, and DC voltage measurement are delivered at the end of the paper.