f, not soft or softer handoff, between cells with different carrier frequencies. CDMA works best on a small grid where short radio links have high path gain. Thus the first carrier is used systemwide, the second carrier is used for all F2 and higher cells, the third carrier is used for all F3 and higher cells, and SO on. Reducing pilot pollution is an engineering issue for each carrier in a CDMA system. If demand patterns dictate an F3 cell layout with a hole in it, an F2 valley in the F3 cells, then we should plug that hole with an F3 cell as a transition cell for the third car- rier. Otherwise, we have the capacity erosion due to the pilot pollution that we have been trying to engineer our system away from. The overall system should be convex, each carrier's coverage should be convex, and the growth-cell grid should be convex. Not only does this keep system capacity high, but it also makes handoff neighbor lists easier to manage. When a call moves from one cell to a cell with fewer carriers, it may need to change carrier with a hard handoff. We say that the call is handed down to the lower carrier.6 Different CDMA equipment vendors hand down calls differently, SO it is important to understand how the equipment actually works. We may have to rely on hard handoff between carriers because soft handoff between carriers is not supported in cdmaOne and may not be supported in the third-generation (3G) systems. If a carrier boundary falls on a busy traffic route, then it may be wise to add a carrier SO that the hand-down boundary is not in such a busy place. The carrier assignment is done well when it meets the traffic, convexity, and hand- down requirements. Each cell should have enough carriers to meet its demand, each carrier should have its coverage area designed to minimize pilot pollution, and the car- rier boundaries should avoid the highest rates of hard handoffs. 33.5 Handling Peak Traffic Demand In designing a wireless system, CDMA or otherwise, we calculate a peak traffic load for each cell sector and make 