Research and Development of Indoor Positioning

Indoor positioning systems have been sufficiently researched to provide location information of persons and devices.This paper is focused on the current research and further development of indoor positioning.The standard evolution and industry development are summarized.There are various positioning systems according to the scenarios,cost and accuracy.However,there is a basic positioning system framework including information extraction,measurement and calculation.In particular,the detailed positioning technologies mainly including cellular positioning and Local Area Network(LAN) positioning are listed and compared to provide a reference for practical applications.Finally,we summarize the challenges of indoor positioning and give a3-phase evolution route.

Measurements and Characterization for the Vehicle-to-Infrastructure Channel in Urban and Highway Scenarios at 5.92GHz

In the future smart transportation system, reliable vehicle-to-infrastructure(V2 I) communication is very important to ensure vehicle driving safety and to improve vehicle driving efficiency. In this paper, V2 I channel measurements at 5.92 GHz are conducted in typical urban and highway scenarios.The frequency and bandwidth of transmission, as well as the deployment of the RSU(roadside unit) and the OBU(on board unit), are selected by considering the recommendation proposed by 3 GPP TR 36.885. Then,based on the measured data, the key channel characteristic parameters of the V2 I channel are extracted,including path loss, root-mean-square delay spread,stationarity distance, and Doppler spread, etc. Also,the statistical characteristics of the parameters, including time-varying and Doppler characteristics, are investigated and characterized. The work in this paper helps researchers design technology and communication systems in similar scenarios.

High-speed railway channel measurements and characterizations: a review

Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

Measurement Analysis of an Indoor Positioning System Based on LTE

Location information is playing an increasing important role in people's life. Specially, indoor positioning systems have been sufficiently researched to provide location information for persons and devices. This paper focuses on the research and development of the indoor positioning system based on LTE uplink signal, which consists of transmitter,Location Measurement Unit (LMU) and server. The Sounding Reference Signal (SRS) is employed as the excitation signal for the estimation of TDOA because of its good autocorrelation. The LMU is used for signal processing and Time-Difference of Arrival (TDOA) calculation,which is connected with four segregate received antennas. Synchronization is not necessary between any two LMUs. Therefore, they can be flexibly deployed on Base Stations (BSs). Additionally, a spatial filtering algorithm without the prior information is proposed to optimize the route tracking. The test results demonstrate that the fixed point positioning error is less than 3m, and the estimated trajectory is basically accordant with the real path in the dynamic test.

Body-force modeling considering induced upstream effects for a transonic compressor with total temperature distortion

To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180circumferential total temperature distortion are performed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.

A novel hybrid CDL-based multipath propagation model for the high-speed railway at 2.35 GHz

In this study,based on the actual channel measurements of the high-speed railway(HSR) in a viaduct scenario at 2.35 GHz,a hybrid cluster delay line(CDL) channel modeling technology which combines a statistical model and a theoretical model is proposed.This novel channel-characterization approach is used to reveal the statistical properties for ‘‘random'' scattering and to provide a geometric mechanism for computing the timevariant paths for ‘‘periodically moving'' scattering.Using a modified clustering algorithm in the delay domain,the inter-cluster and intra-cluster characteristics against the distance between the transmitter and the receiver were extracted and analyzed.In addition,the measurement results were compared with some conclusions from other measurement studies,and the proposed channel model was validated by comparing the simulated results with the measurement data.The study results provide a useful technique for the evaluation and verification of wireless communications in the HSR environment.