Moving calls generate more handoff activity. At the most basic level, this is obvious. Calls that move are likely to be calls that change cells and change MSCs while they change cells. However, moving calls are also calls with rapidly changing radio paths. The handoff itself does not have to happen to keep the signaling network busy sending messages; it suffices that the radio signal levels are close. Moving calls with their greater radio path variation are more likely to trigger handoff measurement messages. As the number of MSCs increases, the amount of border territory increases as well. The more MSC regions there are in the system, the more lines appear on the map sep- arating them from each other, more border zones for more handoff activity. Thus, adding an MSC to the system adds handoff signaling workload as well. The border zone handoff activity increases faster than the number of MSCs. We say that the border area increases at a rate more than linear in the number of MSCs. Go- ing from two to three MSCs adds more border area than going from one to two. And go- ing from three to four MSCs adds more than going from two to three. Each new MSC adds more new border area than the prior addition does. The more-than-linear increase happens because the MSC regions themselves are get- ting smaller as the system serves more traffic. Smaller MSC regions have a greater ra- tio of boundary to area, a simple fact of mathematics that boundary increases with size and area increases with size squared. Subdividing the MSC region into smaller regions keeps the total area the same but creates new border zones. The inter-MSC border zone, that 500-m band we described a few paragraphs back, does not get thinner just because the MSC regions are getting smaller. If the border zone goes through a part of the wireless telephone system with smaller cells, then the handoff zone will be smaller in area. Since we only add small cells where the subscriber traffic density is greater, the total border-zone traffic will be at least as great 