6.1 because most handoff measurements will not result in a handoff. Planning tools can provide more accurate propagation models that may help refine the estimate of the handoff traffic between each pair of MSCs. Handoff traffic between MSCs must use the links dedicated for that purpose. There is no overflow to the PSTN, so it is important to maintain an adequate supply of inter- MSC transport. Once these facilities are full, there are no inter-MSC handoffs even when CDMA radio conditions warrant them. We need to form a confident estimate of the peak-hour amount of inter-MSC hand- offs for each pair of MSCs in the system and plan for transport to meet those needs. suffices to deal with MSCs in a pairwise fashion because three-MSC and four-MSC handoffs still happen two MSCs at a time. 37.1.2 Roamer terminations When a roamer termination appears, an incoming call for a user terminal that is reg- istered somewhere else, the home MSC forwards the call to the serving MSC, where the user terminal can be paged for the call. We can send these roamer terminations through the PSTN to their serving MSCs, but we have the option of using dedicated transport to save the PSTN charges for these calls. The cost saving can be substantial for pairs of MSCs with a lot of roamers between them. In the case of inter-MSC handoffs above, the engineering issue is having enough ca- pacity to support the handoff activity between switches. We certainly want to do this in the most cost-effective manner, but the primary motivation is having the system function, ensuring sufficient capacity so that it will work well. In the case of using ded- icated facilities for terminating roamer calls, the engineering issue is cost reduction be- cause the PSTN is available as an alternate route for overflow. In Sec. 26.3.1 we discussed the design criteria for engineering the dedicated trans- port for roamer terminations. The idea is to use dedicated facilities when the recur- ring cost is less than the PSTN usage costs of traffic it is carrying. Only the bus