 twenty-fifth DS-0 requires another DS-1 and the twenty-ninth DS-1 may require another DS-3. 1 If these backhaul networks are continuing to grow, then we probably should ignore these exceptions. Otherwise, we may end up with a backhaul fan-out network with fully loaded DS-3 or E-3 links that is not well designed for growth. The next new base stations are going to push many of those over their lim- its and make us pay dearly for taking the short-term view on transport costs. For a new base station, we can expect to add a link to a nearby old cell and then to add the new cell's backhaul requirement from the old cell to the MSC. This is usually the best way to grow the backhaul network because it involves the fewest changes and usually keeps transport costs down. We could decide to use the new base station as an intermediate node, a hub in the backhaul network. If it saves enough transport cost, then it makes sense to change the routing from old cells so that their backhaul goes in daisy chains through the new cell. Since this involves significant costs for reconfiguration, the reduction in transport cost has to be enough to pay for the administrative costs and headaches. As a wireless telephone system grows over time, we should evaluate the entire back- haul network periodically from a systemwide perspective. Each new cell adds a new backhaul node, and we incrementally add transport in a locally cost-effective way. How- ever, it is possible for a sequence of good short-term decisions to add up poorly in the long run. If a system of 150 cells grew to 500 cells by adding a few cells at a time, it is possible that the backhaul network can be reconfigured to save a lot of money. Growth and change in our own network are not the only reasons to consider a back- haul overhaul. Transport technologies are changing, and costs are coming down rapidly. Thus a 2-year-old system built on a 2-year-old backhaul plan based on 2-year- old transport prices may be ripe for a new backhaul plan based on current transport technology and 