By cognitive radio,the low Earth orbit(LEO) satellites may prefer to operate in the unlicensed spectrum which is open to all the users,and compete for the limited resources with terrestrial cognitive radio networks(CRNs).The competition can be regarded as a game and analyzed with game theory.This particular unlicensed spectrum sharing problem is modeled here,and the special properties of “spatially-distinguished-interference” and the short period of the interactions between satellites and terrestrial CRNs are explored.Then,the problem is formulated as a “partially-blind” finitely repeated prisoner’s dilemma by game theory.Finally,we begin with two promising spectrum sharing schemes,which can be used to enforce the frequency reuse among the remotely located terrestrial CRN players as well as to overcome the observation noise.By analysis and comparison,it is proposed that the novel refreshing-contrite-tit-for-tat(R-CTFT) is the optimal spectrum sharing scheme.Simulation results verify that it can be used to utilize the spectrum most efficiently. By cognitive radio, the low Earth orbit (LEO) satellites may prefer to operate in the unlicensed spectrum which is open to all the users, and compete for the limited resources with terrestrial cognitive radio networks (CRNs). Competition may be regarded as a game and analyzed with game theory. This particular unlicensed spectrum sharing problem is modeled here, and the special properties of “spatially-distinguished-interference ” and the short period of the interactions between satellites and terrestrial CRNs are explored. Chen, the problem is formulated as a “partially-blind ” finitely repeated prisoner’s dilemma by game theory. Finaally, we begin with two promising spectrum sharing schemes, which can be used to enforce the frequency reuse among the remotely located CRN players as well as to overcome the observation noise.By analysis and comparison, it is proposed that the novel refreshing-contrite-tit-for-tat (R-CTFT) is the optimal spectrum sharing scheme.Simulation results verif y that it can be used to utilize the spectrum most efficiently.