 Some customers get a new cellular telephone because they like the color or style, and others switch services because they like the speed, politeness, and effectiveness of the customer-service department. Al- though engineering does not affect either of these directly, it does have an indirect effect. If cost-effective engineering projects are delivering reliable service on schedule, the whole business benefits. The customer-service department receives fewer problem calls, SO it can do its job better, and more money is available for marketing and design. Our engineering affects the customer's perception of quality in direct ways as well. While engineers may separate quality and capacity, the customers just want things to work right. Excessive call blocking is a capacity issue to an engineer, but it is a QoS is- sue to the customer. High static causing subscribers to hang up in frustration appears at first to be a quality issue. However, in CDMA, that static may be the result of a cell approaching its capacity limit so that too much interference is being generated by other calls. To satisfy customers and increase market share, we must work with the interre- lationships of capacity and quality issues. 17.2 Capacity As we deploy third generation (3G) systems, we need to understand the key principles governing CDMA capacity for data, for voice, and for a combination of voice and data. 17.2.1 Acceptable delay Practical data transmission requirements are very different from voice transmission requirements. As long as a voice call is in progress, there is some level of communica- tion in each direction. 3G systems can take into account the reduced amount of speech and lessen the number of bits transmitted to reduce interference to other calls. How- ever, at any moment, the person may begin speaking again, and voice transmission should resume at the appropriate quality level immediately. Data transmission does not have this requirement. A subscriber might open a data transmission to receive e-mail, reply to it, and send 