现代无线通信系统电波传播_第六章.ppt

6.1 Modeling propagation over rows of buildings 6.1a Components of the path gain 6.1b Modeling PG2 by diffraction of the rooftop fields 6.2 Approaches to computing the reduction PG1 of the rooftop fields 6.2a Physical optics approach to compoting field redution 6.2b Solutions for uniform row spacing and building height 6.3 Plane wave incidence for macrocell predictions 6.3a Soution in terms of Borsmas funtions 6.3b Using the settled field to find the path loss 6.4 Cylindrical wave tincidence for microcell predictions 6.4a Solution in terms of Borsmas funtions 6.4b Path loss for low base station antennas 6.4c Path loss for mobile-to-mobile propagation 6.4d Propagation oblique to rows of buildings 6.5 Numerical evaluation of fields for variable building height and row spacing 6.5a Windowing to terminate the integration 6.5b Discretization of the integration 6.5c Height dependence of the settled field 6.5d Influence of roof shape 6.6 Summary In this chapter we integrate the propagation,reflection,and diffraction concepts of the previous chapters in order to understand an predict the path loss characteristics that have been observed over large portions of metropolitan regions. Transmission loss through a row of houses will be 8 to 14 dB. The radio signal experiences a very large reducetion in strength compared to free-space propagation. Propagation paths in which the waves go over the buildings and are diffracted down to the subscriber may involve less excess path loss. Thinking into account the foregoing discussion,the path gain is the product of three factors: (1) the free-space path gain PG0 (2) the reduction PG1 in the fields arriving at the building near the mobile due to diffraction past the previous rows of buildings (3) the reduction PG2 in the fields as they diffract down to ground level When expressed in decibels, the path gain is The free-space path gain for isotropic antennas is Four possible path We add the pow