 to save a buck, it makes the equation for cost more complicated. Each transport link has several options, some involving purchasing equip- ment up front and others involving leasing facilities from vendors. Some of the vendors are going to offer combinations that make it hard to evaluate the separate cost of each link in the system. In terms of the tradeoff between buying equipment up front and leasing facilities, we should consult the financial planners and ask them how to evaluate this tradeoff. Fi- nancial planners have a set of tools, such as net present value (NPV) calculations. These tools allow them to make decisions that are better for the business. They have their pri- orities, and we want to make sure that we build the system that is most cost-effective according to the needs of those who are paying the bills. There is another reason to con- sult the money people before engineering backhaul with these kinds of tradeoffs. If we are going to make decisions about ongoing expenses, then consulting the executives will encourage them to be part of the process. At least they will feel more comfortable with a decision when they have had a chance to participate. The result of a transport-cost study is a list of all the transport options reduced to costs we can compare. Once corporate priorities are established, fixed costs can be com- pared with recurring expenses, and long-term contracts can be compared with shorter- term commitments. Each transport link option in our calculations should have a clearly defined cost as a function of how many DS-1s or E-1s it is going to carry. 35.2 Fan-out Backhaul Networks Designing an efficient fan-out backhaul network starts with evaluating the transport options from base station to base station. The mathematical model in Sec. 26.1 starts with a cost for every possible connection in a fully-connected, complete graph, so we can start the backhaul engineering process by considering the transport options between every pair of base stations in the entire system. Then we can feed