ty for microcells is in patching pilot-pollution valleys. While we just got through all these discussions of how to avoid pilot pollution, it is still going to happen. The principles of grid-based cellular growth depend on uniform radio propa- gation and availability of good sites for base stations. When these do not occur, the CDMA system will have four- and five-cell zones that may be patched with microcells, particularly when those zones fall in high-density demand areas. The third candidate for a microcell, or perhaps a repeater, is a tunnel, a very deep canyon, or a similar place with a lot of commuters and poor radio access. The spot cov- erage of a microcell allows us to provide seamless service in the macrocell gaps. The local equipment planning job is done when all the opportunities for microcells, picocells, and repeaters have been evaluated. Microcells and picocells are usually small enough to save the cost of separate buildings and towers, so they cost about half as much as full-blown macrocell base stations. They also allow the wireless service provider to promote service in high-density areas that might not be well served with just a macrocell grid. 32.5 Good Cell Locations Now that we have discussed how to make an efficient CDMA cellular grid, it is time to turn our attention to what are good base station locations. Good radio properties for a base station involve clear radio paths to the locations being served and weak radio paths outside the cell. Nature may not be kind enough to offer locations that have per- fect radio performance right to the cell boundary and perfect radio silence outside, but we can look for base station locations that reach their audience well while creating rel- atively little interference for surrounding cells. The result of the analysis of the radio properties of a given area can be plotted on a map. One way to create this plot is to put a mark at the ideal location for each base sta- tion and then to place a small circle around it indicating that any location within the