Dynamic spectrum access: Cyclic transmission exploitation using cognitive radio for coexistence optimized wireless automation systems

The fear of spectrum scarcity in licensed bands or the poor coexisting behavior in unlicensed bands demands the exploration of new resource sharing strategies. As a solution, dynamic spectrum access (DSA) is being addressed to allocate already assigned but sparsely used frequency bands to secondary users without causing any significant interference to primary users. It exploits opportunities in temporal dimension rather than in spectral dimension. Cyclic data transmission is preferred in wireless factory automation systems. We propose the exploitation of this cyclic transmission to implement a DSA based cognitive radio (CR). The CR, working as a secondary user, will operate in the presence of primary users and avoids any harmful interference among coexisting systems. We implemented this idea using both software defined radio (SDR), and conventional hardware defined radio (HDR) based architectures. The experimental results show satisfactory robustness against cyclic interferers.