he cdma2000 wireless networks provide users with a wide range of applications, such as voice, Web browsing, and email. As illustrated in Chapter 2, “Network Architecture,” different applications may require different services. For example, a user requests circuit-switched voice service by pressing the send button after dialing the number of the calling party. After endto-end service is established, the caller and the calling party begin using the voice application. Activating a packet data service for a Web browsing application, however, requires activation of a different set of functions that are not invoked when circuit-switched voice service is established. Due to the limitation of the available spectrum, it is important that the frequency bandwidth is efficiently utilized. It is therefore necessary that the provided service closely matches the needs of the application. For example, email application requires reliable radio connection, but it is delay-tolerant. Hence, the efficiency of the air interface can be maximized at the expense of delay. For that purpose, Radio Link Protocol (RLP) and link adaptation techniques are commonly employed. Voice application is delay-intolerant, so RLP and link adaptation techniques are not acceptable. However, voice application is to some extent error-tolerant, and the air efficiency can be increased at the expense of higher error probability. The availability of a particular application is not only what users care about. Quality of Service (QoS) is also important, because QoS directly impacts user perception about the usefulness of the application.