Gaussian processes. embedded os typically provides an abstraction of Task: Either high-level system tasks which may include system resources and a set of utilities. sensing, communication, processing, and resource al- System performance goal: The abstract characteriza- location, or application tasks which may include de- tion of system properties. Examples include scal- tection, classification, localization, or tracking. ability, robustness, and network longevity, each of Detection: The process of discovering the existence of which may be measured by a set of evaluation a physical phenomenon. A threshold-based detector metrics. may flag a detection whenever the signature of Evaluation metric: A measurable quantity that a physical phenomenon is determined to be significant describes how well the system is performing on enough compared with the threshold. some absolute scale. Examples include packet loss Classification: The assignment of class labels to a set (system), network dwell time (system), track loss of physical phenomena being observed. (application), false alarm rate (application), proba- Localization and tracking: The estimation of the state bility of correct association (application), location of a physical entity such as a physical phenomenon or error (application), or processing latency (applica- a sensor node from a set of measurements. Tracking tion/system). An evaluation method is a process for produces a series of estimates over time. comparing the value of applying the metrics on an Value of information or information utility: A map- experimental system with that of some other ping of data to a scalar number, in the context of benchmark system. Section Four Section Four Section Four Section Four Section Four Section Four Mobile communications This page intentionally left blank Chapter 4.1 Background of 3G evolution Erik Dahlman, Stefan Parkvall, Johan Skold and Per Beming From the first experiments with radio communication by introduced the cellular concept of reusing radio fre- Guglielmo Marconi