Implementation of an opportunistic spectrum access system with disruption QoS provisioning and PU traffic parameter estimation

Opportunistic Spectrum Access (OSA) is one of the models proposed in the literature for Dynamic Spectrum Access (DSA). Providing disruption QoS in terms of interference caused to the Primary Users (PUs) is crucial in such systems. In this paper, we use a residual idle time based scheme called RIBS, to provide disruption QoS to the PUs. The transmission duration of a Secondary User (SU) is carefully computed such that the interference to the PU remains below a threshold. We propose two disruption Quality of Service (QoS) metrics and show the computation of maximum transmission duration for the two metrics. We have implemented RIBS with these two new disruption QoS metrics using GNU Radio over Universal Software Radio Peripheral (USRP) hardware. We also use maximum likelihood estimation (MLE) to dynamically estimate the parameter of PU traffic, which is then used to compute SU transmission duration. This eliminates the requirement, widely assumed in the literature, that SUs know the PU traffic characteristics a priori. Results from our experiments show that RIBS is able to provide the required QoS and that the MLE based parameter estimation method works reasonably well.