Transmission among the cognitive users(CUs)' is always interrupted by the primary users(PUs)' reclaim of the spectrum and the fading effect of wireless channels.To maintain reliable continuous communication am...Transmission among the cognitive users(CUs)' is always interrupted by the primary users(PUs)' reclaim of the spectrum and the fading effect of wireless channels.To maintain reliable continuous communication among CUs,an efficient scheme for link maintenance in OFDM-based cognitive radio Ad Hoc networks is proposed in this paper.In the scheme,redundant sub-channels(RSC) are employed by CUs to tackle the outage problem caused by the PUs' reclaim of the spectrum and wireless fading effect in the transmission.Meanwhile,backup sub-channels(BSC) are arranged to help select sub-channels with better channel quality.Additionally,to lower the overhead and improve the accuracy of the spectrum sensing,a partial sensing module is designed to enable the CUs to inherit and update the original idle spectrum list until it expires.Simulation results show that the proposed scheme can realize higher throughput and lower sensing overhead with slight reduction of the forced termination probability(FTP) performance compared to the existing approaches.展开更多
One critical issue for routing in cognitive radio ad hoc networks (CRAHNs) is how to select a reliable path for forwarding traffic. This is because mobility may cause radio links to break frequently. The reliability o...One critical issue for routing in cognitive radio ad hoc networks (CRAHNs) is how to select a reliable path for forwarding traffic. This is because mobility may cause radio links to break frequently. The reliability of a path depends on the availability of those links that constitutes the path. In this letter, we present a novel approach to predict the probability of the availability of the link between two cognitive radio nodes. The prediction is achieved by estimating the link activation and spectrum activation probabilities. Our prediction is verified by simulation and proved to be accurate. This study can provide reliability assurance on dynamic routing for cognitive radio ad hoc networks.展开更多
Radio links are extensively used for voice and data communications at long distance. We analyze the radio propagation parameters that affect the received signal level on radio links in Rwanda and we determine the best...Radio links are extensively used for voice and data communications at long distance. We analyze the radio propagation parameters that affect the received signal level on radio links in Rwanda and we determine the best path loss model for prediction of the received signal level. Various models of propagation and the mathematical expressions of path loss are described here in order to come to the prediction of those propagation effects. By analyzing data collected for two links of MTN Rwanda: Gahengeri-Kibungo and Gahengeri-Jali, we find that the best predicting model is the normal distribution.展开更多
The effective earth radius factor(k-factor)has a refractive propagation effect on transmitted radio signals thus making its study necessary for the proper planning of terrestrial radio links and power budget.This stud...The effective earth radius factor(k-factor)has a refractive propagation effect on transmitted radio signals thus making its study necessary for the proper planning of terrestrial radio links and power budget.This study was carried out over the city of Lokoja,Nigeria,using ten years(2011 to 2020)atmospheric data of temperature,pressure and humidity both at the surface(12 m)and at 100 m AGL.The data were retrieved from European Centre for Medium-Range Weather Forecasts(ECMWF)ERA5.The k-factor yearly variation follows the same trend with minimum and maximum values obtained during dry and wet season months respectively.In addition,the highest mean value of 1.00042 was recorded in the month of August while the lowest value of 1.00040 was recorded in the month of January with an overall mean value of 1.0003.This value is less than the recommended standard of 1.33 by ITU-R.The propagation effect corresponding to k<1.33 is sub-refractive.The implication of this on radio wave propagation,especially terrestrial communications is that transmitted wireless signal is prone to losses.This can be mitigated through an effective power budget:Choice of transmitting antenna’s height and gain,so as to improve the Quality of Service over the study area.展开更多
This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband un...This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband unit(BBU) on the cloud server. In the system, the baseband signals are precoded at BBU, and then compressed before being transmitted to RRHs through capacity-limited fronthaul links which results in the compressive quantization noise. We assume the regularized zero-forcing precoding is performed with an imperfect channel state information and a compression strategy is applied at BBU. The effect of phase noise arising from nonideal local oscillators both at RRHs and users is considered. We propose an approximate expression for the downlink ergodic sum-rate of considered C-RAN utilizing large dimensional random matrix theory in the large-system regime. From simulation results, the accuracy of the approximate expression is validated, and the effect of phase noise and fronthaul compression can be analyzed theoretically based on the approximate expression.展开更多
飞机通信寻址与报告系统(ACARS,aircraft communication addressing and reporting system)是目前世界范围内使用最广泛的空地数据链通信系统。以激活真实航材的ACARS功能为目的,选择典型的甚高频(VHF,very high frequency)机载电台柯林...飞机通信寻址与报告系统(ACARS,aircraft communication addressing and reporting system)是目前世界范围内使用最广泛的空地数据链通信系统。以激活真实航材的ACARS功能为目的,选择典型的甚高频(VHF,very high frequency)机载电台柯林斯VHF-2100型,从接口规范、数据交互时序关系和电气连接特性3个方面进行研究,设计了ACARS功能的激活方法。通过实验平台的验证,测试结果表明:所设计的方法能够对VHF-2100机载电台进行配置,并能使其收发ACARS报文。真实航材的激活验证了接口控制的可行性,对ACARS机载电台的国产化有一定的借鉴意义。展开更多
当底层无线接入网(Radio Access Network,RAN)发生多链路故障时,为了提高网络切片的恢复能力并且提高网络资源利用率,提出一种基于业务类型的可生存网络切片资源部署(Survivable Network Slice Resource Deployment algorithm Based on ...当底层无线接入网(Radio Access Network,RAN)发生多链路故障时,为了提高网络切片的恢复能力并且提高网络资源利用率,提出一种基于业务类型的可生存网络切片资源部署(Survivable Network Slice Resource Deployment algorithm Based on Service Types,SNSRD-BST)算法。该算法基于节点核心度完成节点映射,区分切片所承载的业务类型。在链路映射阶段,为高可靠、低时延类型切片寻找备份路径,预留备份资源,在故障发生后,如果备份路径可用,则直接迁移至备份路径,否则,采取基于熵权法的多属性路径排序方法进行重映射;对于受故障影响的高带宽类型切片,基于路径资源关键度模型对虚拟链路进行重映射,恢复故障链路。仿真结果表明,在稳定运行后,所提算法的请求接受率为92%,故障恢复率为93%,平均网络故障恢复时延为0.09个时间单元,长期平均收益开销比为0.62,物理链路利用率为63%。与相关算法相比,所提算法的网络切片恢复能力与网络资源利用率较高。展开更多
文章提出了一种基于地理信息系统(Geographic Information System,GIS)呈现的密集城区集中无线接入网络(Centralized Radio Access Network,CRAN)区分裂评估方法。该方法利用GIS技术,通过数据收集和参数GIS呈现,综合评估CRAN区域内微网...文章提出了一种基于地理信息系统(Geographic Information System,GIS)呈现的密集城区集中无线接入网络(Centralized Radio Access Network,CRAN)区分裂评估方法。该方法利用GIS技术,通过数据收集和参数GIS呈现,综合评估CRAN区域内微网格的业务需求和设备接入能力。通过现网环路带宽分析和判断是否需要分裂,制订最优匹配调整CRAN范围和CRAN分裂回传组网的方案,满足网络的健康发展和适应未来需求。该方法为密集城区CRAN网络规划和优化提供了科学的参考和决策依据。展开更多
针对3GPP最新发布的LTE(long term evolution)Release 8标准,研究了LTE空中接口协议栈无线链路控制(radio link control,RLC)的子层确认(acknowledged mode,AM)传输模式的设计与实现机制。主要介绍了LTE无线接入网空中接口协议栈的结构...针对3GPP最新发布的LTE(long term evolution)Release 8标准,研究了LTE空中接口协议栈无线链路控制(radio link control,RLC)的子层确认(acknowledged mode,AM)传输模式的设计与实现机制。主要介绍了LTE无线接入网空中接口协议栈的结构,详细阐述了空中接口协议栈中RLC的AM数据传输模式的运行原理,最后根据协议设计了一种具体在协议栈软件中实现AM传输模式的方法。展开更多
新一代移动通信网络不断演进为高密集、无定型、立体分层的异构网络,移动性管理旨在保证用户设备(user equipment,UE)移动通信服务的连续性和无缝切换及降低信令开销等。移动性管理问题正成为异构小蜂窝网络(heterogeneous and small ce...新一代移动通信网络不断演进为高密集、无定型、立体分层的异构网络,移动性管理旨在保证用户设备(user equipment,UE)移动通信服务的连续性和无缝切换及降低信令开销等。移动性管理问题正成为异构小蜂窝网络(heterogeneous and small cell networks,Het Nets)中无线资源管理需要应对的关键性挑战之一。阐述了移动性管理的一般性问题,根据移动性管理的主要特征给出了一个综合分类:整体切换性能增强、小蜂窝发现与识别增强和无线链路失效(radio link failure,RLF)恢复增强。此外,依据此分类对近年来第三代合作伙伴计划(3rd generation partnership project,3GPP)成员在无线接入网(radio access network,RAN)标准化工作组历次会议中提出的主要移动性管理增强方案进行了分类阐述和性能对比。对异构小蜂窝网络的移动性管理所面临的挑战和未来研究的趋势进行展望,并在此基础上进行了总结。展开更多
提出了一个基于偏振调制的最佳接收灵敏度ROF链路系统。其根本原理在于实现具有最佳光载波边带比(OCSR)的光单边带调制技术,为此,利用偏振调制和滤波技术,线偏光首先经由一个特定偏振角α进入偏振调制器,然后一个固定起偏角β的起偏器...提出了一个基于偏振调制的最佳接收灵敏度ROF链路系统。其根本原理在于实现具有最佳光载波边带比(OCSR)的光单边带调制技术,为此,利用偏振调制和滤波技术,线偏光首先经由一个特定偏振角α进入偏振调制器,然后一个固定起偏角β的起偏器被用来合并偏振信息,最后利用一个光滤波器实现光双边带调制到光单边带调制的转换。研究发现所获得的OCSR只与两个偏振角(α和β)有关,通过仔细调节上述指标,可以将OCSR调谐至最佳值0 d B。利用仿真验证了上述结论,仿真发现通过将OCSR调谐至最佳值将大大提高ROF链路的接收灵敏度。展开更多
基金supported in part by program for National Natural Science Foundation of China under Grant No.61271184863 Program of China under Grant No.2013AA013301New Century Excellent Talents in University under Grant No.NCET-11-0594
文摘Transmission among the cognitive users(CUs)' is always interrupted by the primary users(PUs)' reclaim of the spectrum and the fading effect of wireless channels.To maintain reliable continuous communication among CUs,an efficient scheme for link maintenance in OFDM-based cognitive radio Ad Hoc networks is proposed in this paper.In the scheme,redundant sub-channels(RSC) are employed by CUs to tackle the outage problem caused by the PUs' reclaim of the spectrum and wireless fading effect in the transmission.Meanwhile,backup sub-channels(BSC) are arranged to help select sub-channels with better channel quality.Additionally,to lower the overhead and improve the accuracy of the spectrum sensing,a partial sensing module is designed to enable the CUs to inherit and update the original idle spectrum list until it expires.Simulation results show that the proposed scheme can realize higher throughput and lower sensing overhead with slight reduction of the forced termination probability(FTP) performance compared to the existing approaches.
文摘One critical issue for routing in cognitive radio ad hoc networks (CRAHNs) is how to select a reliable path for forwarding traffic. This is because mobility may cause radio links to break frequently. The reliability of a path depends on the availability of those links that constitutes the path. In this letter, we present a novel approach to predict the probability of the availability of the link between two cognitive radio nodes. The prediction is achieved by estimating the link activation and spectrum activation probabilities. Our prediction is verified by simulation and proved to be accurate. This study can provide reliability assurance on dynamic routing for cognitive radio ad hoc networks.
文摘Radio links are extensively used for voice and data communications at long distance. We analyze the radio propagation parameters that affect the received signal level on radio links in Rwanda and we determine the best path loss model for prediction of the received signal level. Various models of propagation and the mathematical expressions of path loss are described here in order to come to the prediction of those propagation effects. By analyzing data collected for two links of MTN Rwanda: Gahengeri-Kibungo and Gahengeri-Jali, we find that the best predicting model is the normal distribution.
基金National Basic Research Program of China (973 Program) under Grant No. 2006CB303001National High Technology Research and Development Program of China (863 Program) under Grant No. 2007AA01Z2A9+1 种基金CAS Knowledge Innovation Program under Grant No. KGCX2-YW-110-3CAS-Croucher Funding Scheme for Joint Laboratories and Key External Cooperation Program of the Chinese Academy of Sciences under Grant No. GJHZ200819
文摘The effective earth radius factor(k-factor)has a refractive propagation effect on transmitted radio signals thus making its study necessary for the proper planning of terrestrial radio links and power budget.This study was carried out over the city of Lokoja,Nigeria,using ten years(2011 to 2020)atmospheric data of temperature,pressure and humidity both at the surface(12 m)and at 100 m AGL.The data were retrieved from European Centre for Medium-Range Weather Forecasts(ECMWF)ERA5.The k-factor yearly variation follows the same trend with minimum and maximum values obtained during dry and wet season months respectively.In addition,the highest mean value of 1.00042 was recorded in the month of August while the lowest value of 1.00040 was recorded in the month of January with an overall mean value of 1.0003.This value is less than the recommended standard of 1.33 by ITU-R.The propagation effect corresponding to k<1.33 is sub-refractive.The implication of this on radio wave propagation,especially terrestrial communications is that transmitted wireless signal is prone to losses.This can be mitigated through an effective power budget:Choice of transmitting antenna’s height and gain,so as to improve the Quality of Service over the study area.
基金supported in part by the Natural Science Foundation of China (NSFC) under Grant U1805262, 61871446, and 61671251supported by NSFC under Grant 61625106 and Grant 61531011
文摘This paper studies the effect of phase noise and fronthaul compression on a downlink cloud radio access network(C-RAN), where several remote radio heads(RRHs) are coordinated to communicate with users by a baseband unit(BBU) on the cloud server. In the system, the baseband signals are precoded at BBU, and then compressed before being transmitted to RRHs through capacity-limited fronthaul links which results in the compressive quantization noise. We assume the regularized zero-forcing precoding is performed with an imperfect channel state information and a compression strategy is applied at BBU. The effect of phase noise arising from nonideal local oscillators both at RRHs and users is considered. We propose an approximate expression for the downlink ergodic sum-rate of considered C-RAN utilizing large dimensional random matrix theory in the large-system regime. From simulation results, the accuracy of the approximate expression is validated, and the effect of phase noise and fronthaul compression can be analyzed theoretically based on the approximate expression.
文摘飞机通信寻址与报告系统(ACARS,aircraft communication addressing and reporting system)是目前世界范围内使用最广泛的空地数据链通信系统。以激活真实航材的ACARS功能为目的,选择典型的甚高频(VHF,very high frequency)机载电台柯林斯VHF-2100型,从接口规范、数据交互时序关系和电气连接特性3个方面进行研究,设计了ACARS功能的激活方法。通过实验平台的验证,测试结果表明:所设计的方法能够对VHF-2100机载电台进行配置,并能使其收发ACARS报文。真实航材的激活验证了接口控制的可行性,对ACARS机载电台的国产化有一定的借鉴意义。
文摘当底层无线接入网(Radio Access Network,RAN)发生多链路故障时,为了提高网络切片的恢复能力并且提高网络资源利用率,提出一种基于业务类型的可生存网络切片资源部署(Survivable Network Slice Resource Deployment algorithm Based on Service Types,SNSRD-BST)算法。该算法基于节点核心度完成节点映射,区分切片所承载的业务类型。在链路映射阶段,为高可靠、低时延类型切片寻找备份路径,预留备份资源,在故障发生后,如果备份路径可用,则直接迁移至备份路径,否则,采取基于熵权法的多属性路径排序方法进行重映射;对于受故障影响的高带宽类型切片,基于路径资源关键度模型对虚拟链路进行重映射,恢复故障链路。仿真结果表明,在稳定运行后,所提算法的请求接受率为92%,故障恢复率为93%,平均网络故障恢复时延为0.09个时间单元,长期平均收益开销比为0.62,物理链路利用率为63%。与相关算法相比,所提算法的网络切片恢复能力与网络资源利用率较高。
文摘文章提出了一种基于地理信息系统(Geographic Information System,GIS)呈现的密集城区集中无线接入网络(Centralized Radio Access Network,CRAN)区分裂评估方法。该方法利用GIS技术,通过数据收集和参数GIS呈现,综合评估CRAN区域内微网格的业务需求和设备接入能力。通过现网环路带宽分析和判断是否需要分裂,制订最优匹配调整CRAN范围和CRAN分裂回传组网的方案,满足网络的健康发展和适应未来需求。该方法为密集城区CRAN网络规划和优化提供了科学的参考和决策依据。
文摘针对3GPP最新发布的LTE(long term evolution)Release 8标准,研究了LTE空中接口协议栈无线链路控制(radio link control,RLC)的子层确认(acknowledged mode,AM)传输模式的设计与实现机制。主要介绍了LTE无线接入网空中接口协议栈的结构,详细阐述了空中接口协议栈中RLC的AM数据传输模式的运行原理,最后根据协议设计了一种具体在协议栈软件中实现AM传输模式的方法。
文摘新一代移动通信网络不断演进为高密集、无定型、立体分层的异构网络,移动性管理旨在保证用户设备(user equipment,UE)移动通信服务的连续性和无缝切换及降低信令开销等。移动性管理问题正成为异构小蜂窝网络(heterogeneous and small cell networks,Het Nets)中无线资源管理需要应对的关键性挑战之一。阐述了移动性管理的一般性问题,根据移动性管理的主要特征给出了一个综合分类:整体切换性能增强、小蜂窝发现与识别增强和无线链路失效(radio link failure,RLF)恢复增强。此外,依据此分类对近年来第三代合作伙伴计划(3rd generation partnership project,3GPP)成员在无线接入网(radio access network,RAN)标准化工作组历次会议中提出的主要移动性管理增强方案进行了分类阐述和性能对比。对异构小蜂窝网络的移动性管理所面临的挑战和未来研究的趋势进行展望,并在此基础上进行了总结。
文摘提出了一个基于偏振调制的最佳接收灵敏度ROF链路系统。其根本原理在于实现具有最佳光载波边带比(OCSR)的光单边带调制技术,为此,利用偏振调制和滤波技术,线偏光首先经由一个特定偏振角α进入偏振调制器,然后一个固定起偏角β的起偏器被用来合并偏振信息,最后利用一个光滤波器实现光双边带调制到光单边带调制的转换。研究发现所获得的OCSR只与两个偏振角(α和β)有关,通过仔细调节上述指标,可以将OCSR调谐至最佳值0 d B。利用仿真验证了上述结论,仿真发现通过将OCSR调谐至最佳值将大大提高ROF链路的接收灵敏度。
