s that diverse routing costs more money. A truly diverse network has enough surplus capacity to handle the full demand even with a link missing. We may decide to divide the backhaul load along geographically distinct paths so that we get some of our transport when there is a failure, but even this is usually more expensive than a simple fan-out network. Almost any telephone transport network has increas- ing economy of scale, so dividing the load between two paths means operating each path at higher cost per unit transport. Transport facilities do not fail often. We should be able to treat transport failures as rare events rather than routine outages. This allows us to decide which base stations require redundant transport and which cells we are going to protect against these rare failures. The best strategy is probably to have a skeleton network of base stations with geographically diverse transport and to let the rest of the network rely on single trans- port links. This skeleton system should provide good coverage for most of the service area. If a link fails, then there will still be service on the skeleton system, so no large areas will be left without service. No matter what the outcome, the backhaul planning process is only complete when reliability, redundancy, and diverse routing options have been explored. 35.6 Anticipating Growth Backhaul growth is a funny thing. Wireless telephone systems grow by adding cells rather than by growing cells, so the individual serving nodes in the backhaul network 2The industry term for this is backhaul fade. It is the most common source of service failure in the transport network. The consequences, both for PSTN service and for users of leased lines, can be quite severe. A few years ago, New York City lost half of its capacity for calls leaving Manhat- tan due to a dredging error made by the phone company itself. The leased line carrying radar data among the three New York area airports was severed, and all the airports were forced to shut down for several hours. There w