 of radio measurement gives us an accurate picture of radio per- formance, including pilot pollution, cell by cell and place by place. The end result of measurement process is a map nearly as complete as the computer prediction, but with the authenticity of actual measurements. Where the prediction is a guess, the mea- surement is an observation. 39.2 Forward Power Levels The measure of forward-link performance in a CDMA system is how often the base sta- tion transmit amplifier is close to its maximum power. When the CDMA carrier reaches saturation, the power-control loop will keep raising power levels on the channels until the amplifier runs out of power. What we want to get out of transmit power measure- ment is the busy-hour performance of the system, so we need to measure the amplifier power during the busy hour. Watching the power levels at the base station amplifier is our way of knowing how often the CDMA carrier is at or near its breaking point. Amplifier overload is the system telling us about CDMA overload. The curve in Fig. 28.2 shows us how the sys- tem reacts to increasing traffic. When the amplifier reaches half power, we can figure that traffic is getting close to the maximum. It does not matter if the traffic is a lot of voice calls, some real-time video, or a few really big data users. It also does not matter if the event that pushes the CDMA carrier near its limit is a new call, a hand- off, or a change on a neighboring sector. The amplifier power is the indicator we are looking for. 1Back in the Advanced Mobile Phone Service (AMPS) days, we used to drive around in "road ral- lies" making actual calls on cell phones with signal-level meters and channel displays. We would write our location, channel, and signal level as we made telephone calls. Newer technology has specialized equipment for making these measurements. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to t