随着高集成小型化射频技术的发展,多信道定向天线成为提升网络组网容量的新手段,基于此主要研究了无线自组网中基于多信道定向天线的跨层组网协议。以优化的链路状态路由(Optimized Link State Routing,OLSR)协议为基础,充分考察了多信...随着高集成小型化射频技术的发展,多信道定向天线成为提升网络组网容量的新手段,基于此主要研究了无线自组网中基于多信道定向天线的跨层组网协议。以优化的链路状态路由(Optimized Link State Routing,OLSR)协议为基础,充分考察了多信道-单节点各无线信道的时变性质。首先,通过跨层信息共享节点的邻居关系,削减协议开销;其次,跨层获取节点的当前发送速率、负载,并与跳数相结合,设计了一种跨层时变的路由度量方法;最后,充分发挥多信道优势,提出了一种零耦合的多径路由协议。仿真结果表明,所提的多信道跨层多径路由协议能够显著降低网络层的路由开销,提升网络吞吐量。展开更多
Retrieval of multi-layered cloud properties, especially ice water path （IWP）, is one of the most perplexing problems in satellite cloud remote sensing. This paper develops a method for improving the IWP retrievals f...Retrieval of multi-layered cloud properties, especially ice water path （IWP）, is one of the most perplexing problems in satellite cloud remote sensing. This paper develops a method for improving the IWP retrievals for ice-over-water overlapped cloud systems using Tropical Rainfall Measuring Mission （TRMM） Microwave Imager （TMI） and Visible and Infrared Scanner （VIRS） data. A combined microwave, visible and infrared algorithm is used to identify overlapped clouds and estimate IWP separately from liquid water path. The retrieval error of IWP is then evaluated by comparing the IWP to that retrieved from single-layer ice clouds surrounding the observed overlapping systems. The major IWP retrieval errors of overlapped clouds are primarily controlled by the errors in estimating the visible optical depth. Optical depths are overestimated by about 10-40% due to the influence of the underlying cloud. For the ice-over-warm-water cloud systems （cloud water temperature Tw 〉 273 K）, the globally averaged IWP retrieval error is about 10%. This cloud type accounts for about 15% of all high-cloud overlapping cases. Ice-over-super-cooled water clouds are the predominant overlapped cloud system, accounting for 55% of the cases. Their global averaged error is -17.2%. The largest IWP retrieval error results when ice clouds occur over extremely super-cooled water clouds （Tw ≤ 255 K）. Overall, roughly 33% of the VIRS IWP retrievals are overestimated due to the effects of the liquid water clouds beneath the cirrus clouds. To improve the accuracy of the IWP retrievals, correction models are developed and applied to all three types of overlapped clouds. The preliminary results indicate that the correction models reduce part of the retrieval error.展开更多
文摘随着高集成小型化射频技术的发展,多信道定向天线成为提升网络组网容量的新手段,基于此主要研究了无线自组网中基于多信道定向天线的跨层组网协议。以优化的链路状态路由(Optimized Link State Routing,OLSR)协议为基础,充分考察了多信道-单节点各无线信道的时变性质。首先,通过跨层信息共享节点的邻居关系,削减协议开销;其次,跨层获取节点的当前发送速率、负载,并与跳数相结合,设计了一种跨层时变的路由度量方法;最后,充分发挥多信道优势,提出了一种零耦合的多径路由协议。仿真结果表明,所提的多信道跨层多径路由协议能够显著降低网络层的路由开销,提升网络吞吐量。
文摘Retrieval of multi-layered cloud properties, especially ice water path （IWP）, is one of the most perplexing problems in satellite cloud remote sensing. This paper develops a method for improving the IWP retrievals for ice-over-water overlapped cloud systems using Tropical Rainfall Measuring Mission （TRMM） Microwave Imager （TMI） and Visible and Infrared Scanner （VIRS） data. A combined microwave, visible and infrared algorithm is used to identify overlapped clouds and estimate IWP separately from liquid water path. The retrieval error of IWP is then evaluated by comparing the IWP to that retrieved from single-layer ice clouds surrounding the observed overlapping systems. The major IWP retrieval errors of overlapped clouds are primarily controlled by the errors in estimating the visible optical depth. Optical depths are overestimated by about 10-40% due to the influence of the underlying cloud. For the ice-over-warm-water cloud systems （cloud water temperature Tw 〉 273 K）, the globally averaged IWP retrieval error is about 10%. This cloud type accounts for about 15% of all high-cloud overlapping cases. Ice-over-super-cooled water clouds are the predominant overlapped cloud system, accounting for 55% of the cases. Their global averaged error is -17.2%. The largest IWP retrieval error results when ice clouds occur over extremely super-cooled water clouds （Tw ≤ 255 K）. Overall, roughly 33% of the VIRS IWP retrievals are overestimated due to the effects of the liquid water clouds beneath the cirrus clouds. To improve the accuracy of the IWP retrievals, correction models are developed and applied to all three types of overlapped clouds. The preliminary results indicate that the correction models reduce part of the retrieval error.
