Channel Measurement and Modeling in Complex Environments

by Lei Zhang

Institution: TDX
Year: 2016
Keywords: Telecomunicaciones
Posted: 02/05/2017
Record ID: 2135456
Full text PDF: http://oa.upm.es/43353/


The fast development of new technologies such as high-speed rail (HSR) with high reliability, safety and capacity promote the evolution process of corresponding dedicated wireless communication system from narrowband to broadband. The main challenges for the communication system design and network planning in complex environments include: the enclosed space in underground systems; the rapidly time-varying channel in high mobility scenarios, a variety of complex structures in composite scenarios, such as stations, tunnels, cuttings, viaducts, etc.; and the extra losses caused by the vehicle’s structure. Thus, Wireless propagation characteristics in complex scenarios are of importance for the design and implement reliable and efficient communications in modern communication systems. This dissertation analyzes the key challenges for wireless channel characterization in the complex environments. Then a series of propagation measurements conducted in real complex scenarios are presented as the test cases. For the underground system, two typical types of curved tunnels are firstly investigated by the mean of narrowband measurements. The statistical characterization of the path loss exponent, shadow fading distribution, autocorrelation, and cross-correlation are parametrized and compared with different configurations. Furthermore, wideband measurement campaigns conducted in a modern subway system at 980 MHz and 2450 MHz are described in detail. The time dispersion is analyzed with the power delay profile in different regions. The principal parameters, such as mean power and root mean square (RMS) delay are extracted to establish region-based tapped delay line (TDL) models. Moreover, the electromagnetic reverberation in underground system is characterized by the reverberation time, absorption coefficient, and quality factor (Q) as the functions of distance for the first time. Also, the transition distance between station and tunnel is modeled based on the Q versus distance. For high mobility scenarios, a series of wideband measurements carried out in an HSR composite scenario are described. The PDPs are also analyzed to generate the TDL channel models in different regions. Then the corresponding 3D ray-tracing simulation is employed to achieve a deterministic channel model for validating the measurement and also providing the frequency dispersion. The small-scale fading characteristics and the effect of Doppler shift are statistically analyzed. Propagation mechanism inside the mass transit system is another “hot” topic. The study of the outdoor-to-indoor and indoor-to-indoor radio propagation characteristics inside trains is also conducted in this dissertation. Based on the measurements of actual LTE coverage receiving by external and internal antennas, the extra loss caused by the train’s physical structure is estimated. Also, the propagation measurements inside the high-speed train (HST) are presented. Results show the waveguiding effects inside the HST carriage. The log-distance path loss models are parameterized, and…