Spectrum and energy efficient cognitive relay for spectrum leasing

In this paper, we propose a spectrum and energy efficient spectrum leasing scheme based on a two-path successive relay technique. The proposed scheme aims to minimize the primary energy consumption to support a primary target rate while maximizing the secondary rate under an energy budget. Two secondary users are employed to alternately forward the primary signal so as to reduce the transmission time and energy of the primary user. As a reward, after completing the primary signal transmission, the spectrum is leased to secondary users in the remaining time. A utility function that reflects the tradeoff between transmission rate and energy consumption is maximized to determine the optimal time and power allocation. A distributed secondary user selection algorithm is further proposed to select two best secondary users that maximize the utility and then serve as relays for primary system. Simulation results demonstrate that the proposed spectrum leasing scheme significantly reduces the energy cost of primary user and improves the rate of secondary user compared to the conventional relay based spectrum leasing.