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The cdma2000 EV-DO (evolution data only) service was deployed in Korea in 2003. Even though it provides a bandwidth up to almost 1 Mbit/s (enough for delivery of real-time multimedia data), channel quality is time-varying so that service quality should be controlled adaptively. This paper discusses the measurement and analysis of the EV-DO channel quality for fixed or moving terminals. Traces gathered from the experiment are used for modeling channels and generating new traces for the experiment. Analysis shows strong time-lagged correlations between delay, available bandwidth, loss ratio, and acceleration of vehicle. Based on the analysis, it proposes a proxy node that is located in the base station, informs the corresponding node of current channel quality, and converts multimedia data to a form suited to current channel conditions. The proxy node helps the corresponding node to distinguish between the quality of a wired network and that of a wireless channel. Feedback and data conversion policies in the proxy node are determined by service requirements, which depend on service categories such as conversational service or streaming service. Simulation with real-world data shows how well the proxy node satisfies service-dependent QoS (quality of service) requirements. We also use channel information to model a more accurate wireless channel state. Information from the lower layer is useful because it can be used to adapt the channel state more quickly and accurately. The proposed feedback control can be used well with scalable video coding.