ed transport against the cost of sending those calls back out. As we would expect, a new MSC increases the amount of inter-MSC communication. We might not expect the reality that the increase in communication for each new MSC is more than the one before. Another way to think of this more-than-linear increase is to realize that each MSC in the system has an increasing amount of inter-MSC com- munication when a new MSC is added. In Sec. 37.1 we explained how this increases the inter-MSC transport requirement. More MSC regions mean more borders, so we expect more inter-MSC handoffs. And more MSC regions mean smaller regions, SO calls that would be handled within a sin- gle large MSC region are now going to be inter-MSC events. If the MSCs in our system are all in one place, then the transport is a few meters of cable from one switch to another. However, we should not forget that even a few meters of transport cable requires terminating equipment at both ends. This terminating equipment is part of the transport cost, SO even a 10-m cable run incurs some expense. In addition, the MSC has resource limitations as to how many DS-1 or E-1 links it can support, and using more of these for inter-MSC transport means that there are fewer links available for other MSC communication. If the MSCs are not colocated but are on the a common transport backbone, then the transport overhead should remain low. We expect that most wireless system providers in developed areas will have access to a high-capacity transport backbone at the Syn- chronous Optical Network (SONET) level. The MSCs will be located at one or more points of presence (POPs) along the transport backbone. We must make sure that back- bone transport is available. Just because the local telephone company has a lot of transport does not mean that it can lease it to a wireless service provider. All of it al- ready may be leased or committed to other telephone transport customers. Worldwide, wireless telephone service is becoming more popular in places without a large tele