Urban Propagation Modeling for Wireless Systems

摘要

Measurements taken in the San Francisco financial district provide new descriptions of propagation effects and extend existing propagation models to quantify the repeatability of signal variation assumed by new resource allocation techniques. The financial district is a flat portion of the city comprising a grid-like pattern of streets surrounded by buildings up to 160m tall and is like many areas that are now experiencing network congestion. Changes of 15-25 dB in signal strength are known to occur in the vicinity of intersections and along orthogonal streets. Previously not studied, the signal strength's rate of change determines how quickly the system must respond to loss of signal quality. The sudden change in signal level at street corners requires an averaging window of less than 5 wavelengths to determine the local average power. A new partitioning technique incorporates the layout of streets to reduce the prediction error of existing path loss models by up to 6 dB. Using a new model, repeatability of large- and small-scale signal variations is quantified over a 15-month period.