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This paper focuses on the unslotted cognitive radio networks in which the secondary users (SUs) are not synchronized with the primary users (PUs). The SUs can opportunistically utilize the wireless channel as long as the channel is not occupied by the PUs. Due to the half-duplex nature of the wireless medium, the SUs may inevitably impose interference to the PUs because the SUs cannot precisely predict when the PUs becomes active again, and stop transmitting in time. To overcome this challenge, we propose an interference-confined adaptive transmission scheme, which can dynamically adjust the transmission duration of the SUs based on the statistical information of PUs' activity such as to confine the interference with PUs to the acceptable level. Also conducted are extensive simulations to validate and evaluate our proposed scheme. The simulation results show that our proposed scheme can significantly outperform the existing transmission schemes.
Date of Conference: 23-27 May 2010