Synchronized TV whitespace spectrum access

Restrictions on adjacent channel interference leave large swath of spectrum unused. According to FCC, the adjacent channels of an active TV channel are excluded from unlicensed usage. This protection is crucial when estimating the amount of available TV whitespace. By its nature this limitation is technical. Strict primary user protection requirements render most of these adjacent channels unavailable for secondary transmissions. Better technical approaches would open up this reserve. In this paper we propose an OFDM based orthogonal transmission that matches DVB-T frame structure. The proposed scheme allows using immediate adjacent channels without the need of guard bands. We analyze how the proposed scheme generates interference to incumbent TV receivers and what constraints the proposed scheme has to meet. Simulation results show that the proposed scheme provides high signal-to-interference ratio even when the adjacent channel signal is relatively very strong. The scheme is an approach for relaxing the existing adjacent channel usage constraints.