Sahand Haji Ali Ahmad Mingyan Liu Tara Javidi Qing Zhao Bhaskar Krishnamachari Optimality of Myopic Sensing in Multi-Channel Opportunistic Access http://arxiv.org/abs/0811.0637 2008 CoRR abs/0811.0637 db/journals/corr/corr0811.html#abs-0811-0637 informal publication