Return path for interactive TV using white spaces: A novel application for 802.22 WRAN

Interactive TV capitalizes on the opportunities created by digitisation to offer new services. Depending on the level of interactivity, a return path is required to send data from the home user back to the broadcaster. In this paper, we propose the use of 802.22 WRAN to implement the return path over white spaces. Our approach allows the transmission of interactive data in overlay with broadcast data. Following 802.22's requirements, we analyze the task of selecting settings for cooperative spectrum sensing. First, our numerical results show that the number of cooperative devices used to improve sensing accuracy is constrained to the minimum data rate per device. Second, we show through computer simulations that noise uncertainty limits cooperation gains regardless of how settings are selected. Wrapping up our analysis, real-world conditions are considered through testbed experimentation. Measurements confirm that maximum diversity cannot be achieved under correlated shadowing but cooperation may bring advantages if a subset of cooperative devices malfunctions. To the best of our knowledge, this is the first study on the application of 802.22 WRAN as access technology for return paths of interactive TV.