vent. If base sta- tion equipment fails more than twice in a year, then we probably should be switching equipment vendors. And a key component to the redundancy decision is how quickly we can repair a base station once it has an equipment failure. If the base station is at busy shopping mall, then we should be able to dispatch a repair truck in a few minutes. If the base station is on a hill at the end of 1200 m of dirt road outside town, then its repair is going to take longer simply because it takes longer to get there. Transport failures in backhaul should be similarly rare, but we should think about failures there as well. We may have alternate routing in place for the large-cell grid, and we may decide to connect each growth cell to one large cell in the fan-out network. The failure of that one link would bring down the growth cell and cause an outage. If this is sufficiently rare or we can live with the growth-cell outage, then it makes sense not to spend the extra money on diverse transport routing in growth-cell backhaul. The result of a reliability analysis should be a firm plan for redundancy in growth- cell equipment and transport. Such a plan should be based on the frequency and dura- tion of outages and the QoS consequences of those outages. 42.9 Conclusion In this chapter we have addressed when, where, and how to add base stations, creat- ing new cells to improve coverage or to provide enhanced 3G data services. When adding base stations, it is important to pay attention to the allotment of base stations to MSCs and inter-MSC borders, particularly those which are also intersystem borders. For example, we will need to notify neighboring service providers of the need to update their handoff lists, and we may want to cooperate with them when planning border base stations to reduce pilot pollution. 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 a