code division multiple access (CDMA) system performing? Is it serving all customers, or are calls being dropped? Is there room for growth, or is it reaching its limits? Are problems at local spots of poor coverage, cellwide, or systemwide? We want to be able to answer these questions before customers detect problems and before our system becomes overloaded. Periodically, we will want to take radio signal path measurements throughout the coverage area. Also, we will want to monitor a number of crucial statistics in an ongo- ing way and to set alert levels to warn us of problems. Some of the key items to moni- tor are forward and reverse power levels, handoff activity, backhaul congestion, mobile switching center (MSC) performance, signaling capacity, and transport utilization. We will explore each of these in turn, discussing how they are monitored, what the key measures are, and what kind of problems are implied by measurement results that show that a particular measure is outside its normal operating range. 39.1 Radio Signal Path Measurements Knowing the radio environment is an important input to CDMA system design. In the earliest planning stage we start with computer predictions of radio. Once a wireless telephone system is up and running, we can supplement these predictions with mea- surements from the system itself. These measurements help plan for the growth and improvement of the system. We want to know the geographic layout of every cell sector. To do this, we need to know the best radio path, the base station with the highest signal path gain to every (x, y) location in the system. Once we have the best radio path for every place, we can derive the coverage areas for each cell and each sector of each cell. The first step toward complete knowledge of radio propagation in a wireless tele- phone system is running the computer models described in Chap. 47. The computer gives us maps showing us the geographic areas of each cell, the geographic regions served best by each base station. Once we have the best ba