Opportunistic use of radio-frequency spectrum: a network perspective

We address opportunistic use of RF spectrum for communication among frequency-agile nodes composing a network, under the assumptions that the network and its environment are time-varying and users external to the network may have precedence in access and use of certain frequencies under certain conditions. We consider three different frequency assignment problems: (1) finding a common broadcast frequency for a set of nodes, (2) finding a frequency assignment for node pairs that permit interference-free communication, and (3) finding a frequency assignment that enables direct communication between an arbitrary pair of nodes. In all cases, the assignments should yield channels of sufficient quality to permit formation of a connected network and to transport traffic according to services desired, and should not cause unacceptable interference at other users. To solve each problem, we offer both a centralized algorithm that uses global information and a distributed algorithm that uses local information, and we discuss the performance of each