Fast Ray-Tracing for Field Strength Prediction in Cellular Mobile Network Planning

: In this paper we present a fast ray-tracing technique with scalable approximation accuracy for field strength prediction in cellular mobile network planning. Automatic network design methods, like the Adaptive Base Station Positioning Algorithm (ABPA), [2, 3], perform a huge number of field strength estimations and require therefore a fast and accurate approximation. However, common prediction techniques either give only rough estimations or are too complex for fast evaluation, cf. [7]. The proposed new ray-tracing technique obtains its speed-up by taking advantage of the topological information inherent in the used triangulation data structure of the investigated terrain. By that, it is possible to apply simple mathematics and algorithms to trace individual rays. The applicability of the fast ray-tracing technique is demonstrated for both a single transmitter scenario and in conjunction with ABPA. Keywords: mobile communication, network planning, base station location, field stren..

Novel strategies for asymmetric hydrogenation reactions

This thesis describes two novel possibilities for asymmetric hydrogenation: enantioselective hydrogenation using chiral ionic liquid systems and metal-free hydrogenation with boranes. In the first part, asymmetric hydrogenation systems using chiral ionic liquids in combination with racemic rhodium catalyst are presented. Enantioselectivities up to 69% ee were achieved in homogeneous Rh-catalyzed hydrogenation with tropos ligand (BIPHEP, sulfonated BIPHEP) in a proline derived cation chiral ionic liquid as the exclusive source of chiral information. After extraction of product from ionic liquid phase with scCO2, the catalytic system could be reused three times with 70-75% retention of activity and selectivity. In the same chiral ionic liquid, with atropos but racemic ligand BINAP, the hydrogenation of dimethyl itaconate resulted in identical level of enantioselectivity (67% ee) as that obtained with the enantiopure BINAP under the conventional conditions. Kinetic and NMR spectroscopic investigations revealed a chiral poisoning mechanism of this catalytic system. Using racemic BINAP together with an ionic ligand comprising a chiral borate anion, the Rh-catalyzed hydrogenation of dimethyl itaconate led to an enantioselectivity up to 57% ee. The enantiodifferentiation was attributed to diastereomeric formation of ion-pairs between cationic catalyst and the chiral borate anion in this case. In the second part, a novel metal-free catalytic system was developed for the reduction of imines with H2. Simple Lewis acid tris(perfluorophenyl)borane and bis(perfluorophenyl)borane were found to be effective catalysts for hydrogenation of imines at relative mild conditions (80 oC, 20 bar of H2). A thermal induced imine/borane H2-activation mechanism was proposed following the concept of "frustrated Lewis pairs". This catalytic system could be extended to the asymmetric hydrogenation by the employment of chiral borane as catalyst. A number of commercially available and synthesized chiral alkenes were used for the preparation of chiral borane through hydroboration with bis(perfluorophenyl)borane. With these boranes as catalysts, the hydrogenation of imines with H2 led to enantioselectivities up to 57% ee. Camphor derived chiral boranes could be applied in the hydrogen activation together with tri-tert-butylphosphine under mild conditions. Significant enantioselectivities up to 83% ee were obtained for the first time using the "frustrated Lewis pairs" concept with these chiral catalytic systems

Spatial Traffic Estimation and Characterization for Mobile Communication Network Design

This paper presents a new method for the estimation and characterization of the expected teletraffic in mobile communication networks. The method considers the teletraffic from the network viewpoint. The traffic estimation is based on the geographic traffic model, which obeys the geographical and demographical factors for the demand for mobile communication services. For the spatial teletraffic characterization, a novel representation technique is introduced which uses the notion of discrete demand nodes. We show how the information in geographical information systems can be used to estimate the teletraffic demand in an early phase of the network design process. Additionally, we outline how the discrete demand node representation facilitates the application of demand-based, automatic mobile network design algorithms

Field Strength Prediction by Ray-Tracing for Adaptive Base Station Positioning in Mobile Communication Networks

The Adaptive Base Station Positioning Algorithm (ABPA) is presented, which is based on a neural net approximation of the traffic density in the coverage area of a cellular mobile communication system. ABPA employs simulated annealing, thereby achieving quasi-optimal base station locations depending on the topography of the investigated area. Furthermore, ABPA considers the radio wave propagation within this area for the base station positions. Therefore, a three dimensional digital surface model is used to approximate the topography and two field strength prediction methods, a line-of-sight (LOS) approach and a ray-tracing technique, are investigated within the context of adaptive positioning. In particular, the results obtained by the ray-tracing technique are encouraging, showing supplying areas, which seem to be similar to those, stemming from real measurements. However, as simulations show, the more realistic field strength prediction by ray-tracing has a strong influence on the pe..