roximate measure of the reverse call blocking rate. The actual threshold to use can vary, but in the opposite way from the forward direction. A cover- age cell may find itself with one-fifth signal and four-fifths noise when it is nearly over- loaded, whereas a small cell in a dense area may reach two-thirds signal and one-third noise before it gets into capacity trouble. We should be watching the received power levels, either their transmit power levels or the total received power, and looking for signs of saturation. If the busiest period the day has the reverse power threshold crossed 5 percent of the time, then we can pre- sume that we have a peak-time reverse blocking rate of 5 percent. As in the forward direction, we must keep a watch on reverse-direction performance on a regular basis. CDMA's lack of warning and the growth of new services can com- bine to create surprise situations with a short fuse. 39.4 Handoff Activity The handoff activity in a CDMA system is another way to monitor system performance. On the surface, high handoff activity means a high workload for the signaling channel if the handoffs are from one mobile switching center (MSC) to another. However, on the air-interface level, the rate of handoffs tells us a great deal about how well our traffic is using the CDMA air interface. The areas of nearly equal radio propagation are the least-efficient service areas in CDMA. These are the areas where one CDMA channel creates interference on two CDMA carriers. If there are three or four sectors with nearly equal radio performance, then we have pilot pollution, as discussed in Sec. 32.1. It does not take a lot of demand in those areas to use up all the CDMA capacity we have available. An easy measure of the amount of traffic in multiple-cell zones is the amount of handoff activity. After all, what makes a call hand off from one sector to another is that those two sectors have nearly equal radio paths at the point of the handoff. If there are frequent handoff patterns from A to B to C or any other o