be low along the backbone. In such a case, MSC placement depends mostly on the rental cost of the physical location because tele- phone switches are physically large and take up a lot of floor space. Diverse placement of MSCs can protect the wireless telephone system so that some part of it will continue to operate even after a catastrophic local event. However, it does not seem likely that one MSC will be easily able to take over the base stations of an- other in the event of such a failure. Thus, trying to maintain reliability through diverse locations may generate a false sense of security. For the system to be reliable, it has to have diverse backhaul routing as well as reli- able MSC equipment. We could exercise the option of having every base station con- nected to two geographically separate MSCs, but this is going to raise the price of ser- vice significantly and is not likely to produce any noticeable improvement for subscribers. Having one MSC with diverse backhaul routing or at least redundant equipment on the same route is going to produce an improvement in reliability that im- proves service to our subscribers and does so at lower cost. Rather than figure out how to make the MSC network more reliable, it may make more sense to invest in a more reliable configuration for each MSC. Equipment can be duplicated using the models described in Sec. 4.8, or we might have the option of buying better equipment, probably more expensive equipment, that breaks down less often. 43.5 Equipment Provisioning for a New MSC When we install a new MSC in a wireless telephone system, we need to make sure that it has enough equipment to do its job for the system. These are the MSC capacity re- quirements we discussed in Sec. 34.3. Once we have decided on the base station as- signment for a new MSC, we should be able to calculate the equipment required. The main MSC processor has to have enough capacity for all the call processing, SMS, other signaling, and handoffs. Since we are adding a new MSC to serve base sta- tions al