Utility-driven relay for hybrid access femtocells based on cognitive radio spectrum auction

Femtocells promisingly improve coverage and spectrum efficiency at the edge of macrocell. However, macro users may suffer dead-zone trouble due to strong interference coming from closed access femtocell, or compete spectrum resource with femto users in the open access model. In this paper, we propose a novel utility-driven relay scheme adopted by hybrid access femtocell (HAF) to address the above two issues, wherein the macrocell maximizes the usage of its idle spectrum bands, bided by femtocells, via cognitive radio spectrum auction; and recompense relay expense to stimulate selfish femtocells undertaking HAFs to relay the signal to the vicinal macro user, meanwhile avoiding two-tier interference. Spectrum competition among femtocells is formulated as a static Cournot game provided with global information; then necessarily considered as a dynamic Cournot game of the strategy adapting distributively according to the players previous actions. Furthermore, we introduce a protocol and propose refund factor, spectrum price dynamic adjustment algorithms to achieve the Stackelberg equilibrium, i.e., the solution of the non-cooperative game between macrocell and femtocells. We also prove the existence of equilibrium and the convergence of algorithms. Extensive simulation results show the details of games, which indicate they can match the win-win hybrid access mechanism, benefiting cell-edge macro users for better QoS and higher access opportunities for femto users.