I. Introduction
OPPORTUNISTIC spectrum access is a high priority research area, since the limited available spectrum is inefficiently utilized. We consider the problem of nodes in a wireless network that try to gain access to bandwidth by competitively allocating their own transmission power across multiple channels. We specifically study the case where no coordinating entity exists in the network, and nodes seek to arrive at a fair and efficient sharing of available channels in a distributed fashion. Because only local information is available and control signals impose much overhead in environments such as multihop wireless networks, distributed protocols are preferred, which motivates us to employ game theory in the analysis and design of spectrum sharing mechanisms.