Analysis of propagation mechanisms based on direction-of-arrival measurements in urban environments at 2 GHz frequency range
ABSTRACT In cellular mobile communications propagation environments are usually defined roughly by base station location, distance from the base station, and local environment around the mobile station. In this paper a rough categorization of the main propagation mechanisms was done based on the direction of arrival information of each incident wave at the mobile. Three propagation mechanisms, or classes, were specified; propagation along street canyons, propagation directly from transmitter over rooftops in a vertical plane, and other mechanisms as the third class. The first two classes correspond to propagation planes of quasi-3D-models, and the last class presents the proportion of power which quasi 3D-models cannot predict. The categorization is based on a constant elevation boundary for street canyon propagation and tracing of the transmitter's azimuth direction with a small margin for over rooftop propagation. The study of the significance of different propagation mechanisms is based on measurements in several different city environments at 2 GHz frequency range. The measured data consist of microcell and small macrocell measurements and the distance between transmitter and receiver varies from 100 m to 550 m.
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- "In this paper we investigate the SHO probability on or near street crossings in street canyons. We know from various papers ,  that there are two dominant propagation paths in macro-cell scenarios: along the street canyon and deflection over the roof tops. "
ABSTRACT: In this paper we measured the soft-handover (SHO) probability at and near street crossings in UMTS. Literature quotes two main propagation paths in urban macro-cell sce- narios: along street-canyons and over the rooftops. Due to the fact that propagation along street canyons is one of the main propagation paths we expected high SHO probability at street crossings. To evaluate this effect we measured the active-set-size along a route in the city center of Vienna in three different UMTS networks of three different operators. We analyzed the probability of being in SHO-state and the probability of various active-set-sizes for different distances from street crossing s.The results show that probability of being in SHO does not depend on street crossings. I. I NTRODUCTION In this paper we investigate the SHO probability on or near street crossings in street canyons. We know from various papers (1), (2) that there are two dominant propagation paths in macro-cell scenarios: along the street canyon and deflect ion over the roof tops. Entering the crossing, the mobile would monitor a new strong cell propagating within the crossing street canyon. The decision if a new cell is added to the active-set is only based on a window function comparing different received CPICH (Common Pilot CHannel) energy, given by EC/I0. An unrequired increase of the active-set entering street crossings could be likely. After leaving th e street crossing the mobile would drop the new cell. In an area with high traffic, this would introduce significant unrequir ed signaling traffic (see (3), (4)). There are three so called sets in UTRAN (UMTS Terrestrial Radio Access Network). The active-set consists of the cells the mobile is actively connected to. A cell listed in the cell info list, being no member of the active-set, belongs to the monitored-set. The last set is the detected-set. It cont ains all cells from intra frequency measurements. A handover is a mobility event of a mobile station, initiated by the change from cell A to cell B. There are two fundamental types of hand-over (HO). In hard-HO the mobile removes all connections to the old cell before entering the new one. This type of HO applies to all carrier frequency changes (i.e. cel l A and B have different frequencies). In the SHO mode the mobile equipment is logically and physically attached to several base-stations. In this mode it blocks logical and physical resources. Therefore a wrong decision to add a cell to the active-set will harm the UTRAN network performance. The core-network load will increase in SHO mode too. We assumed that the UTRAN is more restricted and therefore did not extract the intra-RNC and intra-SGSN separately. Figure 1 shows a principle scenario. A mobile terminal is moving in a street canyon, on Street1, which is the main propagation path of Cell1, approaching a street crossing with Street2, which is the main propagation path of Cell2. While the terminal is far away from the crossing only Cell1 is visible. When closing in to the crossing also Cell2 will get visible to the receiver and at some point in time the power of the CPICH may be close enough to add Cell2 to the active-set. After leaving the crossing on Stree t1, the power from Cell2 will again drop into the noise floor and Cell2 will be removed from the active-set again. In this case the radio-link addition of the UMTS terminal only generated additional signaling traffic without featuring any improve ment.
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- "been shown to be an insignificant propagation mechanism in Helsinki microcells , . Therefore a two-dimensional city layout is justified for microcellular path-loss prediction. "
ABSTRACT: Based on wideband 5.3 GHz measurements performed in downtown Helsinki, Finland, empirical path-loss models for regular urban street grids were developed for future beyond 3G (B3G) wireless radio systems.IEEE Antennas and Wireless Propagation Letters 01/2007; 5(1-5):152 - 154. DOI:10.1109/LAWP.2006.873950 · 1.95 Impact Factor
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- "The environment was thus small macrocellular. In small macrocellular environments both street canyon propagation and propagation over rooftops to high scatterers are assumed important –. "
ABSTRACT: The urban physical propagation environment around the mobile station is often described as a multipath environment, where power is received through diffractions over rooftops and building corners, reflections from walls and scattering in general from other surrounding objects. Since there are only finite number of these scatterers, the waves are received in clusters each originating from one of the scattering sources. To study these scatterers, direction-of-arrival data measured along continuous routes in two small macrocellular environments were analyzed. Multipaths received with approximately the same directions and delays were combined as clusters. Therefore each of the clusters corresponds to the signal received from one scatterer. This paper focuses on both the identification of the physical scatterers in the surrounding environment and studying the radio wave propagation in more detail, including the amount of significant scatterers in terms of contributed power, XPR values, and delay and azimuth spreads of the individual clusters. The results show that there are only a few dominant scatterers. They were usually building corners and walls, and building structures over the rooftop level. The delay and azimuth spreads inside the clusters were small, and depolarization was almost negligible. Both propagation over the rooftop level and propagation along the street canyons were significant in the considered environments.IEEE Transactions on Antennas and Propagation 01/2006; 53(12-53):4089 - 4098. DOI:10.1109/TAP.2005.859763 · 2.46 Impact Factor