An experimental assessment of transmit opportunities in packet based networks

In this paper we propose a novel suite of transmit opportunity detection methods that effectively exploit the gray space present in high traffic packet networks. Our method adopts a holistic view of the primary network and proactively decides the maximum safe transmit power that does not affect any of the nodes in the primary network. This is achieved via an implicit feedback mechanism from the Primary system to the Secondary system. This is the first time that such a PU-SU feedback link has been shown to naturally arise in the framework of Dynamic Spectrum Access. A novel use of primary packet interarrival duration is developed to rapidly and robustly perform change detection in the primary network's Quality of Service. We develop and evaluate the performance of a battery of tests for such a network state change detection and provide guidelines for transitioning from one test to another in a sequential manner. We thoroughly validate the efficacy of the methods through exhaustive field testing on real world large scale IEEE 802.11 WLAN deployments.