Cooperation based spectrum sharing in cognitive radio networks

In this paper, we propose a cooperative spectrum sharing scheme based on decode and forward relaying and a three phase protocol in cognitive radio networks for a secondary system to access the spectrum concurrent with the primary system. The whole system consists of a pair of primary transmitter (PT) and receiver (PR) and a pair of secondary transmitter (ST) and receiver (SR). PT broadcasts the signal to ST and PR during the first fraction 1 - α of time. ST decodes and regenerates the relaying signal to PR in the second fraction αβ of time and transmits the secondary signal to SR in the third fraction α(1 - β) of time. We consider the case that the channel state information (CSI) is fully known where the secondary system won´t impact the primary transmission by ensuring the achievable rate, and the case that the distance information between each nodes is known where outage performance of the primary system is ensured. The performance of the secondary system is optimized to get optimal α and β. Simulation results illustrate that the proposed scheme can significantly realize spectrum sharing.