In cognitive radio(CR), there is a tradeoff between spectrum sensing time and throughput of secondary user(SU). In the conventional sensing-throughput tradeoff scheme, when the presence of the primary user(PU) is dete...In cognitive radio(CR), there is a tradeoff between spectrum sensing time and throughput of secondary user(SU). In the conventional sensing-throughput tradeoff scheme, when the presence of the primary user(PU) is detected, the SU will stop forwarding data and wait to redetect the PU in the following frame, yielding great throughput loss. In order to improve the SU's throughput, a novel sensing-throughput tradeoff scheme is proposed, which allows the SU to search for a new idle channel through spectrum searching and transfer to this channel to continue communication, when the presence of the PU is detected. An optimization problem is proposed to maximize the SU's throughput in the proposed scheme through jointly optimizing the sensing time, the searching time and the number of available channels, providing that the detection probability to the PU is guaranteed. By fixing the number of channels, based on alternating direction optimization, the joint optimization algorithm of sensing time and searching time is proposed, and then the optimal number of channels is obtained through enumerative searching. The simulation results show that there exist the optimal solutions to the proposed scheme, and the proposed scheme outperforms the conventional scheme notably, with different detection probabilities and sampling frequencies.展开更多
The previous Decentralised Cognitive Medium Access Control(DC-MAC) protocol allows Secondary Users(SUs) to independently search for spectrum access opportunities without the need for a central coordinator.DC-MAC assum...The previous Decentralised Cognitive Medium Access Control(DC-MAC) protocol allows Secondary Users(SUs) to independently search for spectrum access opportunities without the need for a central coordinator.DC-MAC assumes that the detection scheme is ideal at the Physical(PHY) layer.In fact,a more complex detection algorithm is impractical in distributed spectrum sharing scenarios.Energy Detection(ED) at the PHY layer has become the most common method because of its low computational and implementation complexities.Thus,it is essential to integrate the DC-MAC with ED at the PHY layer.However,ED requires the Minimum Sampling Time(MST)duration to achieve the target detection probability in low Signal-to-Noise Ratio(SNR)environments.Otherwise,it cannot achieve the expected detection performance.In this paper,we derive an accurate expression of MST for ED in low SNR environments.Then,we propose an Optimised DC-MAC(ODC-MAC) protocol which is based on MST,and which amends the aforementioned problems of DC-MAC with ED.Moreover,the closed-form expressions for the unreliable data transmission probability are derived for both DC-MAC and ODC-MAC.We show that the simulation results agree well with the theoretical analyses.The proposed ODC-MAC can improve the data transmission reliability and enhance the throughput compared to the performance of the traditional DC-MAC.展开更多
基金supported by the National Natural Science Foundations of China under Grant Nos. 61601221 and 51404211the Natural Science Foundations of Jiangsu Province under Grant No. BK20140828+2 种基金the China Postdoctoral Science Foundations under Grant No. 2015M580425the Natural Science Foundation of Zhejiang Province under Grant Nos. LQ14F010003 and LY14F010009the Fundamental Research Funds for the Central Universities under Grant No. DUT16RC(3)045
文摘In cognitive radio(CR), there is a tradeoff between spectrum sensing time and throughput of secondary user(SU). In the conventional sensing-throughput tradeoff scheme, when the presence of the primary user(PU) is detected, the SU will stop forwarding data and wait to redetect the PU in the following frame, yielding great throughput loss. In order to improve the SU's throughput, a novel sensing-throughput tradeoff scheme is proposed, which allows the SU to search for a new idle channel through spectrum searching and transfer to this channel to continue communication, when the presence of the PU is detected. An optimization problem is proposed to maximize the SU's throughput in the proposed scheme through jointly optimizing the sensing time, the searching time and the number of available channels, providing that the detection probability to the PU is guaranteed. By fixing the number of channels, based on alternating direction optimization, the joint optimization algorithm of sensing time and searching time is proposed, and then the optimal number of channels is obtained through enumerative searching. The simulation results show that there exist the optimal solutions to the proposed scheme, and the proposed scheme outperforms the conventional scheme notably, with different detection probabilities and sampling frequencies.
基金supported by the National Natural Science Foundation of China under Grants No.61271259,No.61301123the Chongqing Natural Science Foundation under Grant No.CTSC2011jjA40006+2 种基金the Research Project of Chongqing Education Commission under Grants No.KJ120501,No.KJ120502,No.KJ130536the Special Fund of Chongqing Key Laboratory(CSTC)the Project of Chongqing Municipal Education Commission under Grant No.Kjzh11206
文摘The previous Decentralised Cognitive Medium Access Control(DC-MAC) protocol allows Secondary Users(SUs) to independently search for spectrum access opportunities without the need for a central coordinator.DC-MAC assumes that the detection scheme is ideal at the Physical(PHY) layer.In fact,a more complex detection algorithm is impractical in distributed spectrum sharing scenarios.Energy Detection(ED) at the PHY layer has become the most common method because of its low computational and implementation complexities.Thus,it is essential to integrate the DC-MAC with ED at the PHY layer.However,ED requires the Minimum Sampling Time(MST)duration to achieve the target detection probability in low Signal-to-Noise Ratio(SNR)environments.Otherwise,it cannot achieve the expected detection performance.In this paper,we derive an accurate expression of MST for ED in low SNR environments.Then,we propose an Optimised DC-MAC(ODC-MAC) protocol which is based on MST,and which amends the aforementioned problems of DC-MAC with ED.Moreover,the closed-form expressions for the unreliable data transmission probability are derived for both DC-MAC and ODC-MAC.We show that the simulation results agree well with the theoretical analyses.The proposed ODC-MAC can improve the data transmission reliability and enhance the throughput compared to the performance of the traditional DC-MAC.
