• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.47-52
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• 2018

Wi-Fi enabled Internet of Things (IoTs) had a substantial impact on society, economy and industry. However wireless connectivity technologies in unlicensed band such as Wi-Fi are vulnerable to interferences. They also face difficulty providing wireless connectivity over long range in dense networks due to the dynamically changed interference effect and asymmetric interference conditions. In this paper, robust acknowledgement transmission scheme is proposed for long range IoTs. According to the proposed scheme, it is possible to control the transmission rate of the transmission success rate of the response frame by adjusting the transmission rate of the response frame when the interference is present asymmetrically. It is also possible to use higher data rate when high quality link is guaranteed. The evaluation results demonstrated the proposed scheme improves the aggregate throughput by at most 9 Mbps when 20 MHz bandwidth transmission mode was adopted.

• Journal of Internet Computing and Services
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• v.12 no.3
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• pp.77-88
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• 2011

In distributed cognitive radio networks, cognitive radio devices which perform the channel sensing individually, are seriously affected by radio channel environments such as noise, shadowing and fading such that they can not property satisfy the maximum allowable interference level to the primary user. In the paper, we propose a Q-learning based channel access scheme for cognitive radios so as to satisfy the maximum allowable interference level to the primary user as well as to improve the throughput of cognitive radio by opportunistically accessing on the idle channels. In the proposed scheme, the pattern of channel usage of the primary user will be learned through Q-learning during the pre-play learning step, and then the learned channel usage pattern will be utilized for improving the sensing performance during the Q-learning normal operation step. Through the simulation, it is shown that the proposed scheme can provide bettor performance than the conventional energy detector in terms of the interference level to primary user and the throughput of cognitive radio under both AWGN and Rayleigh fading channels.