为改善超密集网络中的内容分发效率,提出一种基于协作缓存的内容分发机制。在对小小区基站(Small-cell Base Station,SBS)进行分簇的基础上,由每个簇自主决定内容如何在簇内的SBS进行缓存;其次,在处理用户内容请求时,不仅考虑了簇内协作...为改善超密集网络中的内容分发效率,提出一种基于协作缓存的内容分发机制。在对小小区基站(Small-cell Base Station,SBS)进行分簇的基础上,由每个簇自主决定内容如何在簇内的SBS进行缓存;其次,在处理用户内容请求时,不仅考虑了簇内协作,还考虑了簇间协作,以进一步降低宏基站和移动核心网的负载。仿真结果表明,与无网内缓存以及只有簇内协作的场景相比,该方法可以有效降低内容传输时延,提高内容分发性能。展开更多
考虑了一个基于点对点主通信链路的认知无线供电通信网络(Wireless Powered Communication Network,WPCN),该认知WPCN由一个多天线混合接入点组成,该接入点将无线能量传输给一组低功耗无线设备,并接收来自这些无线设备的传感数据。为了...考虑了一个基于点对点主通信链路的认知无线供电通信网络(Wireless Powered Communication Network,WPCN),该认知WPCN由一个多天线混合接入点组成,该接入点将无线能量传输给一组低功耗无线设备,并接收来自这些无线设备的传感数据。为了解决认知WPCN中固有的用户不公平问题,同时考虑到同相/正交不平衡、非线性放大幅度和相位噪声对低成本传感器节点物理收发器的影响,提出了一个基于非线性能量收集的簇协作协议,从而平衡不同无线设备的能量消耗,提高了认知WPCN系统的吞吐量性能。为了保证主系统的性能,考虑了主系统的温度干扰约束,在三种实际网络环境下进行了仿真,结果表明,该方法能有效提高认知WPCN的吞吐量公平性,同时保证了主网络的通信质量。展开更多
To deal with a sharp increase in transmission energy consumption due to the presence of a large number of secondary users( SUs),an energy-efficient cooperative spectrum sensing results transmission scheme is proposed ...To deal with a sharp increase in transmission energy consumption due to the presence of a large number of secondary users( SUs),an energy-efficient cooperative spectrum sensing results transmission scheme is proposed for cognitive radio systems. First,a cluster-based structure is introduced into the sensing results transmission scheme to reduce the transmission power. Then,the centralized sensing results transmission model is employed,and the non-fixed code rate Luby transform( LT)code is selected as the channel coding since its code rate can dynamically adapt to channel conditions and therefore avoid unnecessary redundancy in the transmission power.Furthermore,an improved optimal degree distribution( ODD)is designed for the LT code. The simulation results show that the choice of the appropriate parameters in degree distribution is very helpful for the LT code to achieve a promising performance. The ODD with optimized parameters can achieve more than 2 d B performance gain than other typical degree distributions when the bit error rate( BER) is 10-3. The energy consumption of the proposed scheme is not only at least71. 4% lower than that of the non-coding system,but also lower than that of the convolutional coding system with different code rates. Meanwhile, the energy consumption can be further reduced in the case that a suitable clustering method is selected.展开更多
The biosynthesis of antibiotics is controlled by cascade regulation involving cluster-situated regulators (CSRs) and pleiotropic regulators. Three CSRs have been identified in the jadomycin biosynthetic gene cluster, ...The biosynthesis of antibiotics is controlled by cascade regulation involving cluster-situated regulators (CSRs) and pleiotropic regulators. Three CSRs have been identified in the jadomycin biosynthetic gene cluster, including one OmpR-type activator (JadR1) and two TetR-like repressors (JadR* and JadR2). To examine their interactions in jadomycin biosynthesis, a series of mutants were generated and tested for jadomycin production. We noticed that jadomycin production in the jadR*-jadR2 double mutant was increased dramatically compared with either single mutant. Transcriptional analysis showed that jadR* and jadR2 act synergistically to repress jadomycin production by inhibiting the transcription of jadR1. Furthermore, jadR* and jadR2 reciprocally inhibit each other. The complex interactions among these three CSRs may provide clues for the activation of the jadomycin gene cluster, which would otherwise remain silent without stimulation from stress signals.展开更多
文摘为改善超密集网络中的内容分发效率,提出一种基于协作缓存的内容分发机制。在对小小区基站(Small-cell Base Station,SBS)进行分簇的基础上,由每个簇自主决定内容如何在簇内的SBS进行缓存;其次,在处理用户内容请求时,不仅考虑了簇内协作,还考虑了簇间协作,以进一步降低宏基站和移动核心网的负载。仿真结果表明,与无网内缓存以及只有簇内协作的场景相比,该方法可以有效降低内容传输时延,提高内容分发性能。
文摘考虑了一个基于点对点主通信链路的认知无线供电通信网络(Wireless Powered Communication Network,WPCN),该认知WPCN由一个多天线混合接入点组成,该接入点将无线能量传输给一组低功耗无线设备,并接收来自这些无线设备的传感数据。为了解决认知WPCN中固有的用户不公平问题,同时考虑到同相/正交不平衡、非线性放大幅度和相位噪声对低成本传感器节点物理收发器的影响,提出了一个基于非线性能量收集的簇协作协议,从而平衡不同无线设备的能量消耗,提高了认知WPCN系统的吞吐量性能。为了保证主系统的性能,考虑了主系统的温度干扰约束,在三种实际网络环境下进行了仿真,结果表明,该方法能有效提高认知WPCN的吞吐量公平性,同时保证了主网络的通信质量。
基金The National Natural Science Foundation of China(No.61771126)the Foundation of Graduate Innovation Center in NUAA(No.kfjj20170402)
文摘To deal with a sharp increase in transmission energy consumption due to the presence of a large number of secondary users( SUs),an energy-efficient cooperative spectrum sensing results transmission scheme is proposed for cognitive radio systems. First,a cluster-based structure is introduced into the sensing results transmission scheme to reduce the transmission power. Then,the centralized sensing results transmission model is employed,and the non-fixed code rate Luby transform( LT)code is selected as the channel coding since its code rate can dynamically adapt to channel conditions and therefore avoid unnecessary redundancy in the transmission power.Furthermore,an improved optimal degree distribution( ODD)is designed for the LT code. The simulation results show that the choice of the appropriate parameters in degree distribution is very helpful for the LT code to achieve a promising performance. The ODD with optimized parameters can achieve more than 2 d B performance gain than other typical degree distributions when the bit error rate( BER) is 10-3. The energy consumption of the proposed scheme is not only at least71. 4% lower than that of the non-coding system,but also lower than that of the convolutional coding system with different code rates. Meanwhile, the energy consumption can be further reduced in the case that a suitable clustering method is selected.
基金supported by grants from the Ministry of Science and Technology of China (2013CB734001, 2009CB118905)the National Natural Science Foundation of China (31270110, 31030003)
文摘The biosynthesis of antibiotics is controlled by cascade regulation involving cluster-situated regulators (CSRs) and pleiotropic regulators. Three CSRs have been identified in the jadomycin biosynthetic gene cluster, including one OmpR-type activator (JadR1) and two TetR-like repressors (JadR* and JadR2). To examine their interactions in jadomycin biosynthesis, a series of mutants were generated and tested for jadomycin production. We noticed that jadomycin production in the jadR*-jadR2 double mutant was increased dramatically compared with either single mutant. Transcriptional analysis showed that jadR* and jadR2 act synergistically to repress jadomycin production by inhibiting the transcription of jadR1. Furthermore, jadR* and jadR2 reciprocally inhibit each other. The complex interactions among these three CSRs may provide clues for the activation of the jadomycin gene cluster, which would otherwise remain silent without stimulation from stress signals.
