Dynamic Spectrum Access (DSA) allows unlicensed wireless devices to opportunistically access unoccupied licensed spectrum bands. DSA yields efficient spectrum utilization which can greatly improve wireless networking performance. In this paper, we advocate application-awareness to effectively manage the sideeffects of DSA that can offset its benefits by adversely impacting application QoS. Simple application hints are found to be able to serve as key inputs in evaluating current spectrum

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... ons relative to application needs, leading to an informed DSA mechanism that minimizes the impact of undesirable DSA side-effects. Towards this goal, we propose a wireless service architecture called Context-Aware Spectrum Agility (CASA). The key elements of CASA are: (a) semantic dependency equations that provide the relationship between application-layer QoS state and lower-layer DSA parameters, (b) CASA Algorithm that adapts DSA parameters and activities to better suit application needs, and, (c) a low overhead interface to provide application context to DSA. CASA has been explicitly designed with the goals of practical deployment, low overhead operation, and is compatible with any DSA protocol. Compared to state-of-art DSA, the deployment of CASA along with DSA protocols is shown to improve QoS metrics, such as delay and jitter, by an average of 30 and 64%, respectively. CASA is also found to match the application QoS demands for more than 90% of the duration of a communication session-a 300?% improvement over conventional application-agnostic DSA.