Harnessing cross-layer-design

Applications and protocols for wireless and mobile systems have to deal with volatile environmental conditions such as interference, packet loss, and mobility. Utilizing cross-layer information from other protocols and system components such as sensors can improve their performance and responsiveness. However, application and protocol developers lack a convenient way of specifying, monitoring, and experimenting with optimizations to evaluate their cross-layer ideas. We present crawler, a novel experimentation architecture for system monitoring and cross-layer-coordination that facilitates evaluation of applications and wireless protocols. It alleviates the problem of complicated access to relevant system information by providing a unified interface to application, protocol and system information. The versatile design of this interface further enables a convenient and declarative way to specify and experiment with compositions of cross-layer optimizations and their adaptions at runtime. crawler also provides the necessary support to detect cross-layer conflicts, and hence prevents performance degradation when multiple optimizations are enabled across the protocol stack. We demonstrate the usability of crawler for system monitoring and cross-layer optimizations with three use cases from different areas of wireless networking.