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We study the bit and power-allocation problem for an orthogonal frequency-division multiplexing (OFDM)-based cognitive radio (CR) system in which the spectrum is licensed to a primary user (PU) pair consisting of one transmitter and one receiver. CR pairs (CRPs) may use both active and nonactive PU bands as long as the generated interference powers are within the interference temperature limits of the PUs. The optimal solution and a low-complexity suboptimal solution are proposed. It is found that significant improvements can be achieved compared with systems in which CRPs only use the nonactive PU bands.