With the rapid growth of wireless broadband technologies, such as WLAN and WiMAX, quality streaming video contents are available through portable devices anytime, anywhere. The layered multicast system using scalable ...With the rapid growth of wireless broadband technologies, such as WLAN and WiMAX, quality streaming video contents are available through portable devices anytime, anywhere. The layered multicast system using scalable video codecs has been proposed as an efficient architecture for video dissemination taking account of user and link diversities. However, in the wired/wireless combined best-effort based heterogeneous IP networks which provide more fluctuation in available bandwidth and end-to-end delay, the performance of streaming systems has been greatly degraded due to frequent packet loss, resulting from either wired congestion or wireless fading/shadowing. In this paper, we present a real-time embedded packet train probing scheme for estimating end-to-end available bandwidth so as to accomplish effective congestion and error control. This is facilitated by effective classification of packet loss sources, delay trend detection algorithm and flexible transmission rate of packets. Under the proper wireless channel modelling and estimation, our layered structure can allow appropriate subscription of video layers and adaptively insert necessary amount of forward error correction (FEC) packets so as to achieve QoS optimized system for scalable video multicasting.展开更多
LTE(long term evolution,长期演进)系统中采用了咬尾卷积码和Turbo码来实现前向纠错,Viterbi译码是卷积码的一种杰出的译码算法,它是一种最大似然译码方法。本文基于LTE系统中的咬尾卷积码,详细分析了几种较成熟的Viterbi译码算法,并...LTE(long term evolution,长期演进)系统中采用了咬尾卷积码和Turbo码来实现前向纠错,Viterbi译码是卷积码的一种杰出的译码算法,它是一种最大似然译码方法。本文基于LTE系统中的咬尾卷积码,详细分析了几种较成熟的Viterbi译码算法,并综合现有算法,提出了一种改进算法,减小了译码计算的复杂度。仿真结果表明,改进算法在降低译码计算复杂度的同时还降低了译码误比特率,因此非常适合LTE系统的译码要求。展开更多
介绍用于光纤通信的速率为2.5 G b/s的高速RS(255,239)译码器设计。对输入信号中可能出现的超出译码器纠错能力的误码可进行检测判断,保证了误码不扩散。对译码器中大量使用的有限域乘法器进行了优化设计,尤其对并行钱氏搜索电路中的乘...介绍用于光纤通信的速率为2.5 G b/s的高速RS(255,239)译码器设计。对输入信号中可能出现的超出译码器纠错能力的误码可进行检测判断,保证了误码不扩散。对译码器中大量使用的有限域乘法器进行了优化设计,尤其对并行钱氏搜索电路中的乘法器采用了按组优化设计方法,与直接实现方法相比,复杂度降低了45%。该RS译码器已用FPGA进行了功能验证,并用TSM C 0.18μm CM O S工艺实现,Synopsys综合后的仿真结果表明译码器电路时钟工作频率达到了330 MH z。展开更多
文摘With the rapid growth of wireless broadband technologies, such as WLAN and WiMAX, quality streaming video contents are available through portable devices anytime, anywhere. The layered multicast system using scalable video codecs has been proposed as an efficient architecture for video dissemination taking account of user and link diversities. However, in the wired/wireless combined best-effort based heterogeneous IP networks which provide more fluctuation in available bandwidth and end-to-end delay, the performance of streaming systems has been greatly degraded due to frequent packet loss, resulting from either wired congestion or wireless fading/shadowing. In this paper, we present a real-time embedded packet train probing scheme for estimating end-to-end available bandwidth so as to accomplish effective congestion and error control. This is facilitated by effective classification of packet loss sources, delay trend detection algorithm and flexible transmission rate of packets. Under the proper wireless channel modelling and estimation, our layered structure can allow appropriate subscription of video layers and adaptively insert necessary amount of forward error correction (FEC) packets so as to achieve QoS optimized system for scalable video multicasting.
文摘LTE(long term evolution,长期演进)系统中采用了咬尾卷积码和Turbo码来实现前向纠错,Viterbi译码是卷积码的一种杰出的译码算法,它是一种最大似然译码方法。本文基于LTE系统中的咬尾卷积码,详细分析了几种较成熟的Viterbi译码算法,并综合现有算法,提出了一种改进算法,减小了译码计算的复杂度。仿真结果表明,改进算法在降低译码计算复杂度的同时还降低了译码误比特率,因此非常适合LTE系统的译码要求。
文摘介绍用于光纤通信的速率为2.5 G b/s的高速RS(255,239)译码器设计。对输入信号中可能出现的超出译码器纠错能力的误码可进行检测判断,保证了误码不扩散。对译码器中大量使用的有限域乘法器进行了优化设计,尤其对并行钱氏搜索电路中的乘法器采用了按组优化设计方法,与直接实现方法相比,复杂度降低了45%。该RS译码器已用FPGA进行了功能验证,并用TSM C 0.18μm CM O S工艺实现,Synopsys综合后的仿真结果表明译码器电路时钟工作频率达到了330 MH z。
