Abstract-- In this work, we propose a game theoretic framework to analyze the behavior of cognitive radios for distributed adaptive channel allocation. We define two different objective functions for the spectrum sharing games, which capture the utility of selfish users and cooperative users, respectively. Based on the utility definition for cooperative users, we show that the channel allocation problem can be formulated as a potential game, and thus converges to a deterministic channel allocation Nash equilibrium point. Alternatively, a no-regret learning implementation is proposed for both scenarios and it is shown to have similar performance with the potential game when cooperation is enforced. In addition, the learning algorithm accommodates selfish users, and requires less knowledge about the game and less implementation overhead. We show that cooperation based spectrum sharing etiquette improves the overall network performance at the expense of an increased overhead required for ...