Available Bit Rate (ABR) service has been developed to support data applications to asynchronous transfer mode (ATM) networks.Since a ratebased feedback flow control mechanism has been selected as a standard by ATM Fo...Available Bit Rate (ABR) service has been developed to support data applications to asynchronous transfer mode (ATM) networks.Since a ratebased feedback flow control mechanism has been selected as a standard by ATM Forum,buffering becomes an issue that needs intensive study.In this paper,the queuing performance in a switch is studied in detail.It is theoretically proven that the goals of no cell loss and full utilization of link capacity can be achieved by choosing an appropriate buffersize and threshold of the switch buffer which is supported by our simulation results of a complex network.展开更多
Dynamic spectrum access (DSA) scheme in Cognitive Radio (CR) can solve the current problem of scarce spectrum resource effectively, in which the unlicensed users (i.e. Second Users, SUs) can access the licensed spectr...Dynamic spectrum access (DSA) scheme in Cognitive Radio (CR) can solve the current problem of scarce spectrum resource effectively, in which the unlicensed users (i.e. Second Users, SUs) can access the licensed spectrum in opportunistic ways without interference to the licensed users (i.e. Primary Users, PUs). However, SUs have to vacate the spectrum because of PUs coming, in this case the spectrum switch occurs, and it leads to the increasing of SUs’ delay. In this paper, we proposed a Variable Service Rate (VSR) scheme with the switch buffer as to real-time traffic (such as VoIP, Video), in order to decrease the average switch delay of SUs and improve the other performance. Different from previous studies, the main characteristics of our studying of VSR in this paper as follows: 1) Our study is on the condition of real-time traffic and we establish three-dimension Markov model;2) Using the internal optimization strategy, including switching buffer, optimizing buffer and variable service rate;3) As to the real-time traffic, on the condition of meeting the Quality of Service(QoS) on dropping probability, the average switch delay is decreased as well as improving the other performance. By extensive simulation and numerical analysis, the performance of real-time traffic is improved greatly on the condition of ensuring its dropping probability. The result fully demonstrates the feasibility and effectiveness of the variable service rate scheme.展开更多
列级读出电路是目前提升平面图像传感器读出效率最为明显的方式,但是对于亿级像素超大面阵规模下的大数据大负载高速读出,列级到输出级并串转换中的列级缓冲设计面临极大的挑战.本文提出一种基于双反馈环路的列级缓冲设计方法,该方法通...列级读出电路是目前提升平面图像传感器读出效率最为明显的方式,但是对于亿级像素超大面阵规模下的大数据大负载高速读出,列级到输出级并串转换中的列级缓冲设计面临极大的挑战.本文提出一种基于双反馈环路的列级缓冲设计方法,该方法通过在列级缓冲的近端输出与远端输出间实现双反馈环路,有效抑制了列级总线的超大寄生参数对建立时间的影响,同时确保了低噪声高动态下的模拟信号精度.基于55 nm互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)工艺,在一款12288×12288像素规模的红外图像传感器中进行了成功的应用,结果表明:与传统列级缓冲相比,本文提出的双反馈环路列级缓冲设计方法可以将上升建立时间缩短23.4%,下降建立时间缩短21.9%,亿级高速图像传感器的帧率提升29.6%.展开更多
文摘Available Bit Rate (ABR) service has been developed to support data applications to asynchronous transfer mode (ATM) networks.Since a ratebased feedback flow control mechanism has been selected as a standard by ATM Forum,buffering becomes an issue that needs intensive study.In this paper,the queuing performance in a switch is studied in detail.It is theoretically proven that the goals of no cell loss and full utilization of link capacity can be achieved by choosing an appropriate buffersize and threshold of the switch buffer which is supported by our simulation results of a complex network.
文摘Dynamic spectrum access (DSA) scheme in Cognitive Radio (CR) can solve the current problem of scarce spectrum resource effectively, in which the unlicensed users (i.e. Second Users, SUs) can access the licensed spectrum in opportunistic ways without interference to the licensed users (i.e. Primary Users, PUs). However, SUs have to vacate the spectrum because of PUs coming, in this case the spectrum switch occurs, and it leads to the increasing of SUs’ delay. In this paper, we proposed a Variable Service Rate (VSR) scheme with the switch buffer as to real-time traffic (such as VoIP, Video), in order to decrease the average switch delay of SUs and improve the other performance. Different from previous studies, the main characteristics of our studying of VSR in this paper as follows: 1) Our study is on the condition of real-time traffic and we establish three-dimension Markov model;2) Using the internal optimization strategy, including switching buffer, optimizing buffer and variable service rate;3) As to the real-time traffic, on the condition of meeting the Quality of Service(QoS) on dropping probability, the average switch delay is decreased as well as improving the other performance. By extensive simulation and numerical analysis, the performance of real-time traffic is improved greatly on the condition of ensuring its dropping probability. The result fully demonstrates the feasibility and effectiveness of the variable service rate scheme.
基金Supported by National Natural Science Foundation of China（60434030,60673178,and 60472076） and National Basic Research Program of China（973 Program）（2007CB307106）
文摘列级读出电路是目前提升平面图像传感器读出效率最为明显的方式,但是对于亿级像素超大面阵规模下的大数据大负载高速读出,列级到输出级并串转换中的列级缓冲设计面临极大的挑战.本文提出一种基于双反馈环路的列级缓冲设计方法,该方法通过在列级缓冲的近端输出与远端输出间实现双反馈环路,有效抑制了列级总线的超大寄生参数对建立时间的影响,同时确保了低噪声高动态下的模拟信号精度.基于55 nm互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)工艺,在一款12288×12288像素规模的红外图像传感器中进行了成功的应用,结果表明:与传统列级缓冲相比,本文提出的双反馈环路列级缓冲设计方法可以将上升建立时间缩短23.4%,下降建立时间缩短21.9%,亿级高速图像传感器的帧率提升29.6%.
