Providing disruption QoS in an OFDM system using Residual Idle Time Based opportunistic spectrum access

Dynamic spectrum access (DSA) is emerging as a promising technology to mitigate spectrum scarcity caused by static frequency allocation. Among the different models proposed for DSA, opportunistic spectrum access (OSA) is a promising class of solutions. In any DSA system, it is important to make sure that the performance of primary users (PUs) does not degrade significantly as a result of dynamic use of spectrum by secondary users (SUs). One of the main reasons for slow commercial adoption of OSA technology is the lack of system implementations which can demonstrate bounding interference to PUs below a given threshold. In this paper, we report a preliminary implementation of an OSA scheme which can ensure that the interference to the PU is bounded. We present our experience and challenges in building this system using the open source software toolkit GNU Radio on a software defined radio (SDR) implemented with a Universal Software Radio Peripheral (USRP).