The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the pe...The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the performance and identifying its bottleneck in such systems can shed light on the system design and performance optimization. TCP performance of a commercial crowdsourced live streaming system is examined by analyzing packet-level traces collected at streaming servers. TCP stalls that heavily hurt the Qo E of user have been identified. In particular,the TCP stalls account for as much as 31. 6% of the flow completion time for upload flows and result in abandonment of upload on the corresponding channels. Stalls caused by timeout retransmissions are further dissected and timeout retransmission characteristics are revealed to be dependent on the video encoding methods. These findings provide new insights in crowdsourced live streaming systems and can guide designers to improve the TCP efficiency.展开更多
TCP/IP is a next generation key technology in the wireless communication network where the different characteristics of wireless and wired links result in performance degradation. We can use the proxy and automatic re...TCP/IP is a next generation key technology in the wireless communication network where the different characteristics of wireless and wired links result in performance degradation. We can use the proxy and automatic repeat request (ARQ) schemes to deal with this problem. In this work, we investigate the TCP performance over proxy and ARQ in the wireless network. Our analysis results showed that using the proxy can result in lower transfer latency and higher throughput and that ARQ can decrease the loss rate of wireless link and improve the performance with little additional latency. The analytical results were validated against simulations using the NS-2 with some more realistic parameters.展开更多
为实现无线远距离测试放大器幅频特性的功能,设计了一种无线远程幅频特性测试系统。系统以STM32单片机和Cyclone IV FPGA构成的最小系统为主控,由可调信号源模块、带自动增益的幅频特性测试单元、显示部分、Wifi模块、上位机TCP服务器...为实现无线远距离测试放大器幅频特性的功能,设计了一种无线远程幅频特性测试系统。系统以STM32单片机和Cyclone IV FPGA构成的最小系统为主控,由可调信号源模块、带自动增益的幅频特性测试单元、显示部分、Wifi模块、上位机TCP服务器解析与幅频曲线显示部分构成。测试结果表明,示波器以及上位机可有效地显示带宽达40 MHz、步进频率为1 MHz的幅频特性曲线。系统具有结构简单、稳定性好、人机界面友好的特点。展开更多
基金Supported by the National Basic Research Program of China(2012CB315801)the National Natural Science Foundation of China(No.6157060397)
文摘The prevalence of smart phone and improvement of wireless net promote the usage of crowdsourced live streaming,where individual users act as live streaming sources to broadcast themselves online. Characterizing the performance and identifying its bottleneck in such systems can shed light on the system design and performance optimization. TCP performance of a commercial crowdsourced live streaming system is examined by analyzing packet-level traces collected at streaming servers. TCP stalls that heavily hurt the Qo E of user have been identified. In particular,the TCP stalls account for as much as 31. 6% of the flow completion time for upload flows and result in abandonment of upload on the corresponding channels. Stalls caused by timeout retransmissions are further dissected and timeout retransmission characteristics are revealed to be dependent on the video encoding methods. These findings provide new insights in crowdsourced live streaming systems and can guide designers to improve the TCP efficiency.
文摘TCP/IP is a next generation key technology in the wireless communication network where the different characteristics of wireless and wired links result in performance degradation. We can use the proxy and automatic repeat request (ARQ) schemes to deal with this problem. In this work, we investigate the TCP performance over proxy and ARQ in the wireless network. Our analysis results showed that using the proxy can result in lower transfer latency and higher throughput and that ARQ can decrease the loss rate of wireless link and improve the performance with little additional latency. The analytical results were validated against simulations using the NS-2 with some more realistic parameters.
文摘为实现无线远距离测试放大器幅频特性的功能,设计了一种无线远程幅频特性测试系统。系统以STM32单片机和Cyclone IV FPGA构成的最小系统为主控,由可调信号源模块、带自动增益的幅频特性测试单元、显示部分、Wifi模块、上位机TCP服务器解析与幅频曲线显示部分构成。测试结果表明,示波器以及上位机可有效地显示带宽达40 MHz、步进频率为1 MHz的幅频特性曲线。系统具有结构简单、稳定性好、人机界面友好的特点。
