io links from two cells for one call. The signal matrix describes the radio environment the way the CDMA equations in Sec. 28.1.2 described the CDMA radio interference. The rows and columns of the two matrices are similar in structure. We can think of the signal matrix as the foundation environment that the CDMA equations are built on. 47.9 Radio Propagation Maps The result of a propagation study is typically a collection of visual maps telling cellu- lar engineers what is going on in their systems. These maps can tell us about existing systems, or they can predict what a system is going to look like before we build it. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Propagation Models Propagation Models The most basic map shows the most likely server for each (x, y) location in the ser- vice area. Each base station is assigned a color, and the blobs of color on the map cor- respond to the regions served. We picture these maps as having regular-shaped cover- age areas with smooth boundaries between them. When the most likely server map has a fuzzy boundary between two base stations or, worse, areas specked with different col- ors because the path-prediction algorithms come up with different base stations from bin to bin, the cellular engineer should be looking closely at that area to determine if the system will provide adequate CDMA service. A radio path gain map shows strong and weak coverage areas. If we use green for good coverage, yellow for marginal coverage, and red for no coverage as we did in Sec. 40.2, then we can see a big green circle around each base station with some yellow ar- eas between base stations. If there are significant red areas, then we have areas where the system might provide no service at all. Our final example of CDMA planning maps is the pilot-pollution map showing areas of nearly equal radio signal paths from m