Research on Adaptive Threshold of Received Signal in Communication System

When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.

The Study of RAIM Performance by Simulation

Receiver Autonomous Integrity Monitoring （RAIM） is a software algorithm available in some GPS receivers which gives an indication if the position solution given by the GPS receiver is suitable to use. The detail algorithm of the parity space method of RAIM technique is presented. Using FDI and FDE methods, the simulations of RAIM performance have been done in three different phases independently with respect to the bias of the fault satellite. Case study of simulation results is discussed and each performance of RAIM is analyzed. According to the analysis of simulation results, the parity space method of RAIM can meet the integrity requirements for nonprecision, terminal and enroute flight phase. It also indicates that the results of performance of FDE are better than that of FDI.

Redirected jumping in virtual scenes with alleys

Background The redirected jumping(RDJ)technique is a new locomotion method that saves physical tracking area and enhances the body movement experience of users in virtual reality.In a previous study,the range of imperceptible manipulation gains in RDJ was discussed in an empty virtual environment(VE).Methods In this study,we conducted three tasks to investigate the influence of alley width on the detection threshold of jump redirection in a VE.Results The results demonstrated that the imperceptible distance gain range in RDJ was not associated with the width of the alleys.The imperceptible height and rotation gain ranges in RDJ are related to the width of the alleys.Conclusions We preliminarily summarized the relationship between the occlusion distance and manipulation range of the three gains in a complex environment.Simultaneously,the guiding principle for choosing three gains in RDJ according to the occlusion distance in a complex environment is provided.

Analysis of secondary throughput and optimization in cooperative spectrum sensing

In cooperative spectrum sensing, more secondary user makes more opportunity for detecting the vacant spectrums, which resulting the spectrum utilization improved, however much bandwidth would be occupied for sending the local observation results, inducing the reduced secondary throughput. In this paper, an adaptive algorithm for selecting detection threshold was proposed, where the maximized secondary throughput can always be achieved while assuring sufficient protection to primary user, regardless of the number of sensing users in cognitive radio networks. Theoretical analysis and simulation results validate the proposed scheme.