r C added, we have a three-way soft handoff among A, B, and C. When sector B is dropped, we have a soft handoff between A and C. We can calculate the soft-handoff states over time from the add and drop events that we observe. The result of tracking soft-handoff states from soft-handoff add and drop events is to find the time calls spent in various states of soft-handoff. We can add up all the soft- handoff state times during the busy hour and determine which sector combinations have high soft-handoff activity levels. We should do this calculation for sector pairs, triplets, and combinations of four or more. When we see a combination of four or more sectors with high soft-handoff activity, this is a loud warning sign that there is a capacity problem. The geographic area where those calls are coming from is a pilot-pollution zone that is a good candidate for a new cell. 39.4.2 Inter-MSC handoffs We should measure handoffs between MSC areas as well. The wireless telephone sys- tem should give us counts of inter-MSC hard handoffs and inter-MSC soft-handoff events if the vendor's equipment supports inter-MSC soft handoffs. We can measure signaling activity by counting not only the inter-MSC handoffs but also all the inter-MSC handoff measurement messages. The total message count for each MSC is part of the signaling load and should be used to make sure that we main- tain enough signaling capacity. If the handoff message load is higher than we predicted in the system planning stage, then we may need to add some signaling facilities. The other side of inter-MSC handoffs is the inter-MSC transport to support them. Here we care how much time calls are spending in inter-MSC handoff because this de- termines how much inter-MSC transport capacity they are using. High handoff rates that were not foreseen in our forecasts can use up our inter-MSC facilities. The conse- quence of this is the loss of ability to do handoffs from one MSC to another, a serious consequence. We can watch the global handoff rates to and from one MSC, 