IP网络QoS实现技术研究

文章主要研究基于多协议标记交换(MPLS)技术和区分服务(DiffServ)／资源预留协议(RSVP)结合模型的IP网络服务质量(QoS)实现技术。首先根据带宽代理(BB)模型给出一种简化的QoS体系结构，然后着重讨论该结构中的4个主要模块：RSVP模块、DiffServ模块、MPLS模块和BB控制模块。在ns-2．26上的仿真表明，该方案有效地改善了丢包率和时延这二个QoS性能指标。     

基于Matlab的OFDM调制解调系统仿真实验

本文在介绍OFDM调制解调技术原理的基础上,给出了基于Matlab仿真平台的OFDM调制解调系统仿真框图,详细介绍了关键模块的具体仿真实现方法,包括信号产生模块、基带调制模块、串并变换模块、IFFT模块等.最后对OFDM调制解调系统性能进行了仿真和分析,结果验证了本文给出的仿真模型的正确性、合理性.     

基于FPGA的Turbo码译码器的设计

主要论述了一种基于FPGA的Turbo码译码器的设计。首先简单介绍了编码器和交织器的原理;然后介绍了基于Max-Log-MAP算法的译码器原理,对分量译码器做了详细论述,给出了各子模块原理和ModelSim仿真图形;最后给出了系统仿真的误码率图形。     

一种基于FPGA的判决反馈均衡器

论述了一种基于现场可编程门阵列( FPGA)的判决反馈均衡器的设计.首先介绍了判决反馈均衡器的原理,然后给出了Simulink仿真的电路和仿真结果,介绍了用分布式算法(DA)来实现滤波器的原理和各模块原理,最后给出Modelsim仿真结果.     

基于System View仿真的MSK调制解调技术

运用System View软件对MSK调制解调信号进行仿真。仿真根据MSK的原理框图进行模块的选择和连接、设置参数、系统的设计、给出主要部分的仿真结果,与理论结果进行对比,确定仿真结果的准确性。     

EOS应用中VLAN删除模块的设计与实现

本文介绍了以EOS(Ethernet over SDH)应用中VLAN删除模块的设计与实现,讨论了其工作原理及主要模块电路的设计思想,给出了主要模块电路的仿真结果,结果表明本文设计达到了预期的设计目标.     

全数字64QAM调制器的FPGA实现

通过对QAM调制原理的分析,提出了一种基于FPGA全数字64QAM调制方案,该方案采用Verilog HDL硬件描述语言进行模块设计。文中对其主要模块进行了详细分析,并给出了各模块的仿真图,以正确实现全数字64QAM调制。     

基于FPGA的井下有线遥感勘测通信模块的设计

文章介绍了用FPGA设计油井有线遥感勘测通信模块的方法及遥感勘测通信模块的工作原理 ,给出了在MAX +PLUSⅡ平台下的仿真波形     

基于EPM570的可逆直流调速模块设计

针对经济型直流电机调速应用,采用EPM570T100C5芯片设计了一个通用的、可远程控制的可逆调速模块。调压主回路采用两组双向可控硅、二极管桥式整流电路。介绍了CPLD实现调速的优点和双向可控硅调速原理,给出了模块组成框图,采用Verilog HDL语言和自顶向下的设计方法设计了主模块和速度检测、速度控制、RS 485等子模块,给出了调速子模块的仿真波形。仿真和实验数据表明,模块可精确产生可控硅控制脉冲,有效调节转速,实现较小的误差。     

基于Simulink的箔条走廊干扰仿真系统

采用Simulink仿真技术,对箔条走廊干扰过程和干扰效果进行了动态的信号级仿真。进行了作战场景想定,建立了箔条走廊对雷达干扰的模型体系结构,给出了仿真模块框图。给出了箔条走廊干扰的原理及数学模型,对仿真结果进行了对比分析。仿真结果表明,箔条走廊散射杂波可以压制常规脉冲雷达,箔条走廊对电磁波的衰减可以使MTD体制雷达接收不到目标回波。     

Architecture and experimental results for quality of service in mobile networks using RSVP and CBQ

Efforts are underway to enhance the Internet with Quality of Service (QoS) capabilities for transporting real‐time data. The issue of wireless networks and mobile hosts being able to support applications that require QoS has become very significant. The ReSerVation Protocol (RSVP) provides a signaling mechanism for end‐to‐end QoS negotiation. RSVP has been designed to work with wired networks. To make RSVP suitable for wireless networks, changes need to be made by: (i) changing the way control messages are sent, and (ii) introducing wireless/mobile specific QoS parameters that take into account the major features of wireless networks, namely, high losses, low bandwidth, power constraints and mobility. In this paper, an architecture with a modified RSVP protocol that helps to provide QoS support for mobile hosts is presented. The modified RSVP protocol has been implemented in an experimental wireless and mobile testbed to study the feasibility and performance of our approach. Class Based Queueing (CBQ) which is used as the underlying bandwidth enforcing mechanism is also modified to fit our approach. The experimental results show that the modified RSVP and CBQ help in satisfying resource requests for mobile hosts, after handoff occurs. The experiments also show how different power and loss profile mechanisms can be used with our framework. The system performance using the modified RSVP control mechanism is also studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quality-of-service mechanisms in all-IP wireless access networks

In this paper, we focus on resource reservation protocol (RSVP)-based quality-of-service (QoS) provisioning schemes under Internet protocol (IP) micromobility. We consider QoS provisioning mechanisms for on-going RSVP flows during handoff. First, the rerouting of RSVP branch path at a crossover router (CR) at every handoff event can minimize resource reservation delays and signaling overheads, and in turn the handoff service degradation can be minimized. We show that RSVP branch path rerouting scheme could give a good tradeoff between the resource reservation cost and the link usage. Second, the new RSVP reservation can be made along the branch path toward the CR via a new base station in advance, while the existing reservation path is maintained, and in turn the on-going flow can be kept with the guaranteed QoS. We also show that seamless switching of RSVP branch path could provide the QoS guarantee by adaptively adjusting the pilot signal threshold values. Third, during RSVP resource reservation over wireless link, dynamic resource allocation scheme is used to give a statistical guarantee on the handoff success of on-going flows. We finally obtain the forced termination probability of guaranteed service flows, the average system time of best effort flows by using a transition rate matrix approach.     

基于RSVP-TE的组播信令协议的实现机制及性能研究

对自动交换光网络（AsON）中基于RSVP—TE的组播扩展进行了研究。提出了在现有信令架构上实现组播功能的几个关键问题，并就基本技术进行了讨论。在此基础上，介绍了4个RSVP—TE协议扩展模型，并通过仿真详细比较了它们的开销和性能。文中的理论分析和仿真结果对光网络中组播协议的设计和选择提供了重要的参考依据。     

Analyses of soft‐state signaling protocols in GMPLS‐Based WDM networks

Wavelength‐routed Generalized Multi‐Protocol Label Switching (GMPLS) networks use Resource reSerVation Protocol—Traffic Engineering (RSVP‐TE) as signaling protocol to set up and tear down lightpaths. RSVP‐TE uses a soft‐state control mechanism to manage lightpaths. In the soft‐state control mechanism, each node sets a timer for each control state and resets the timer with refresh messages to maintain the state. When the timer expires due to losses of refresh messages, the control state is initialized and a reserved resource managed with the state is released. It has been considered that resource utilization of soft‐state protocols is inferior to that of hard‐state protocols, since soft‐state protocols may reserve resources until control states are deleted due to timeout. Therefore, some extensions to promote the performance of soft‐state protocols, such as message retransmission, have been considered. In this paper, we analyze the behavior of GMPLS RSVP‐TE and its variants with a Markov model and analyze the performance of RSVP‐TE. From the results, we demonstrate that resource utilization of RSVP‐TE can be equivalent to that of a hard‐state protocol when the loss probability of signaling messages is low. We also investigate the effectiveness of message retransmission and show that using message retransmission leads to poor resource utilization in some cases. Copyright © 2012 John Wiley & Sons, Ltd.     

Common spatio-temporal pattern for single-trial detection of event-related potential in rapid serial visual presentation triage

Searching for target images in large volume imagery is a challenging problem and the rapid serial visual presentation (RSVP) triage is potentially a promising solution to the problem. RSVP triage is essentially a cortically-coupled computer vision technique that relies on single-trial detection of event-related potentials (ERP). In RSVP triage, images are shown to a subject in a rapid serial sequence. When a target image is seen by the subject, unique ERP characterized by P300 are elicited. Thus, in RSVP triage, accurate detection of such distinct ERP allows for fast searching of target images in large volume imagery. The accuracy of the distinct ERP detection in RSVP triage depends on the feature extraction method, for which the common spatial pattern analysis (CSP) was used with limited success. This paper presents a novel feature extraction method, termed common spatio-temporal pattern (CSTP), which is critical for robust single-trial detection of ERP. Unlike the conventional CSP, whereby only spatial patterns of ERP are considered, the present proposed method exploits spatial and temporal patterns of ERP separately, providing complementary spatial and temporal features for high accurate single-trial ERP detection. Numerical study using data collected from 20 subjects in RSVP triage experiments demonstrates that the proposed method offers significant performance improvement over the conventional CSP method (corrected p-value < 0.05, Pearson r = 0.64) and other competing methods in the literature. This paper further shows that the main idea of CSTP can be easily applied to other methods.     

RSVP Extensions for Real-Time Services in Hierarchical Mobile IPv6

The Mobile IPv6 (MIPv6) provides many great features, such as sufficient addressing space, mobility, and security; MIPv6 is one of the most important protocols for next generation mobile Internet. Simultaneously, with the rapid improvement of wireless technologies, the real-time multi-media IP services such as video on demand, videoconference, interactive games, IP telephony and video IP phone will be delivered in the near future. Thus, to furnish accurate QoS for real-time services is one of the most important thing in the next generation mobile Internet. Although RSVP, which is a resource reservation protocol, processes signaling messages to establish QoS paths between senders and receivers, RSVP was originally designed for stationary networks and not aware of the mobility of MNs. Therefore, this paper proposes a novel RSVP extension to support real-time services in Hierarchical Mobile IPv6 (HMIPv6) environments. For intra-site mobility, the concept of QoS Agent (QA) is proposed to handle the RSVP QoS update messages and provide the advanced reservation models for real-time services. For inter-site mobility, IP multicast can help to invite inter-site QAs to make pre-reservation and minimize the service disruption caused by re-routing the data path during handover. Simulation results show that the proposed scheme over HMIPv6 is more suitable for real-time services than the famous RSVP tunnel-based solution.     

Reliable RSVP path reservation for multimedia communications under an IP micromobility scenario

We focus on how quality of service (QoS) guarantees can be provided for RSVP flows during handoff events in an IP micromobility network. For this purpose, RSVP message delays and signaling overheads should be minimized, and handoff service disruption should also be minimized. By rerouting the RSVP branch path at a crossover router at every handoff event, and establishing the new RSVP path between the CR and new BS in advance while the existing reservation path is maintained, ongoing RSVP flows can be kept with the guaranteed QoS. We propose the seamless switching of an RSVP branch path for soft handoff, and also show that this scheme could provide QoS guarantee with simulation and examples.     

Collected experience from implementing RSVP

Internet quality of service (QoS) is still a highly debated topic for more than fifteen years. Even with the large variety of QoS proposals and the impressive research advances, there is little deployment yet of network layer QoS technology. One specific problem domain is QoS signalling, which has recently attracted increasing attention to bring forward new standardization approaches. In this paper, an extensive study of RSVP is presented, covering protocol design, software design, and performance aspects of the basic version of RSVP and of certain standardized and experimental extensions. This work is based on and presents the experience from implementing RSVP for UNIX systems and the ns-2 simulation environment. The implementation includes a variety of protocol extensions and incorporates several internal improvements. It has been subject to extensive functional and performance evaluations, the results of which are reported here.     

基于非线性服务曲线的RSVP资源分配方式

本文主要针对基于RSVP的保证服务，讨论了如何利用非线性服务曲线进行资源分配，以实现带宽和时延要求的解耦。提出了一种简单有效的非线性服务曲线，数值分析结果表明就资源利用率而言，其性能远远优于传统的线性服务曲线。最后论文讨论了未来的发展趋势并给出了有待研究的一些课题。     

Dynamic RSVP protocol

RSVP is a resource reservation setup protocol that can be used by a host to request specific QoS for multicast multimedia flows on the Internet. Multiprotocol label switching (MPLS) architecture also needs RSVP. The fact that the resolutions of the display system used in different receiver nodes might have different, multi-resolution characteristics is supported in the MPEG-4 standard, and the EZW compression algorithm can cease decoding at any point in the bitstream. However, RSVP does not provide a more flexible mechanism. In this article we propose an extension of RSVP to provide the needed mechanism, coined dynamic RSVP (DRSVP), to dynamically adjust reserved resources on nodes without much effort. It provides different video resolutions to different receiver nodes with different needed reserved resources. Therefore, it does not waste precious Internet resources to transmit unnecessary multimedia packets.