首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 93 毫秒
1.
黄华华  邱小军 《电声技术》2007,31(4):53-55,58
VoIP的语音质量受到丢包、延时、时延抖动等因素影响。为提高语音质量,需要进行丢包补偿处理,如采用WSOLA算法。首先介绍了WSOLA算法的原理,然后提出了用PAOLA对其进行优化的方法,最后对恢复语音质量进行了比较。  相似文献   

2.
本文首先考虑丢包率的控制方案,然后讨论VoIP网关对丢包率的监测,最后在简单带宽调整算法的基础上提出一种改进的控制算法——传输速率自适应调整算法,并将算法运用到VoIP系统中,提出一种自适应变速率语音编码器,来控制语音包的丢失。  相似文献   

3.
黄存东  陈秀忠 《电声技术》2007,31(6):67-69,72
讨论了网络拥塞对VoIP应用的影响,基于VoIP应用的特征,提出了一种新的适应于VoIP队列的主动丢包的调度算法——VASA算法。结合VASA和RED算法可实现新的VoIP队列管理和调度模式,从而可以有效改善网络拥塞状态下语音包转发的性能。  相似文献   

4.
IPTV的QoS/QoE受到IP网络丢包的影响是非常大的,丢包问题其实是在IP网络上,特别是在开放Internet环境和无线网络中提供流媒体服务所面临的最大挑战之一。本文从分析丢包现象及其对于IPTV的影响入手,分析比较了几种用于降低丢包造成影响的策略和相关的技术,以及国际标准中在相关领域的最新动态。  相似文献   

5.
在基于IP网络下进行语音通信的过程中,不可避免地会遇到数据包丢失现象,极大地影响了传输服务的质量。对此问题展开讨论,讲述了丢包的原因,对当前普遍采用的几种丢包恢复技术进行了介绍,通过比较提出了自己的观点。  相似文献   

6.
基于SIP协议的VoIP系统的QoS机制的研究   总被引:1,自引:0,他引:1  
IP电话是一种数字电话,是技术创新的一种通信服务业务,它把语音、压缩编码、打包分组、分配路由、存储交换、解包解压等各种交换处理组合在IP网或互联网上实现语音通信。因特网语音通信是VoIP技术的一个最典型的,也是最有前景的应用领域。介绍了VoIP的通信原理、关键技术和系统通信中的SIP协议,分析了影响VoIP的QoS的主要原因,阐述了时延、抖动、丢包和回声等影响QoS的机理和解决方案。  相似文献   

7.
黄晋维  鲍长春 《信号处理》2021,37(10):1791-1798
实时IP 语音通信在数据包会丢失的情况下,语音质量会受到严重影响。为了恢复传输过程中丢失的语音信息,本文提出了一种基于瞬时相位差(Instantaneous Phase Deviation, IPD)和深度神经网络(Deep Neural Network, DNN)的丢包隐藏 (Packet Loss Concealment, PLC)方法。在训练阶段,将语音的对数功率谱(Log Power Spectrum, LPS)和IPD作为训练DNN的输入特征,以学习从接收包到丢失包的映射关系;在重构阶段,将丢包前接收到的语音包送入训练好的DNN中,恢复出丢失包的语音。实验结果表明,在不同丢包率下,所提方法的性能优于传统的基于LPS和DNN的PLC方法。   相似文献   

8.
网络流量丢包率预测模型   总被引:1,自引:0,他引:1  
周磊 《无线电工程》2011,41(10):7-8,20
无线信道的网络流量的及时预测,是目前国内外研究的前沿课题。通过对实时网络流量的测量分析,提出了一种基于最小二乘法的多项式拟合网络流量丢包率预测模型。该模型根据当前获得的网络流量信息,对网络丢包率趋势进行预测,为无线网络下信号丢包率的预测供了可行的手段。实测丢包率与预测丢包率的对比分析表明提出的预测模型能很好的预测丢包率趋势。  相似文献   

9.
为解决游戏中的延迟和丢包问题,以游戏加速技术为研究对象,分析了游戏延迟和丢包对游戏体验的影响,并介绍了游戏加速技术的应用。首先,对游戏延迟进行了定义和原因分析,并讨论了延迟对游戏体验的影响以及测量和评估方法。其次,对丢包进行了定义和原因分析,并探讨了丢包对游戏流畅性和稳定性的影响。再次,介绍了基于游戏延迟和丢包问题的游戏加速技术应用。最后,总结了研究成果并提出展望,旨在为相关人员和工程提供参考,以改善游戏体验并提升游戏网络性能。  相似文献   

10.
利用Inernet传输语音,能够提高网络资源的利用率,具有很多优点,但目前Qos还很难保证。本文提出采用联合速率/差错控制模型,同时使用基于发送端的丢包恢复和基于接收端的语音平滑技术,增强了语音抗丢包能力。还采用网络状态反馈技术,使得FEC的冗余方式能够随着网络状态的变化而变化。这个模型不仅能提高服务质量。还能更有效的利用网络资源。  相似文献   

11.
An important issue for video transmission over IP networks is the preservation of perceived video quality despite packet loss. Packet loss can be detrimental to compressed video. However, reducing packet loss to a very low level is difficult with current techniques. Furthermore, even a very low objective loss probability can still seriously distort perceived video quality. This paper presents a packet scheduling scheme at a router which addresses the loss issues of networked video. Experiments using real video data show that the proposed scheme can significantly improve the visual quality of video and network efficiency. Moreover, it can provide different classes of videos with different levels of loss guarantees, while maintaining service fairness among the same class of videos.  相似文献   

12.
A survey of packet loss recovery techniques for streaming audio   总被引:4,自引:0,他引:4  
Perkins  C. Hodson  O. Hardman  V. 《IEEE network》1998,12(5):40-48
We survey a number of packet loss recovery techniques for streaming audio applications operating using IP multicast. We begin with a discussion of the loss and delay characteristics of an IP multicast channel, and from this show the need for packet loss recovery. Recovery techniques may be divided into two classes: sender- and receiver-based. We compare and contrast several sender-based recovery schemes: forward error correction (both media-specific and media-independent), interleaving, and retransmission. In addition, a number of error concealment schemes are discussed. We conclude with a series of recommendations for repair schemes to be used based on application requirements and network conditions  相似文献   

13.
A mobile ad hoc network is an autonomous system of infrastructure-less, multihop, wireless mobile nodes. Reactive routing protocols perform well in this environment due to their ability to cope quickly against topological changes. This paper proposes a new routing protocol named CHAMP (caching and multiple path) routing protocol. CHAMP uses cooperative packet caching and shortest multipath routing to reduce packet loss due to frequent route failures. We show through extensive simulation results that these two techniques yield significant improvement in terms of packet delivery, end-to-end delay and routing overhead. We also show that existing protocol optimizations employed to reduce packet loss due to frequent route failures, namely local repair in AODV and packet salvaging in DSR, are not effective at high mobility rates and high network traffic.  相似文献   

14.
An important issue for video transmission over IP networks is preservation of perceived video quality despite packet loss. Packet loss can be detrimental to compressed video. However, reducing packet loss to a very low level is difficult with current loss control techniques. Furthermore, even a very low objective loss probability can still seriously distort perceived video quality. This paper presents two buffer management schemes using video characteristics. They increase maximum loss tolerance for a desired level of video quality, providing better quality at equal loss ratios, when compared to a conventional buffer management scheme. Meanwhile, service fairness and network efficiency are also improved.  相似文献   

15.
End-to-end Internet packet dynamics   总被引:2,自引:0,他引:2  
We discuss findings from a large-scale study of Internet packet dynamics conducted by tracing 20000 TCP bulk transfers between 35 Internet sites. Because we traced each 100-kbyte transfer at both the sender and the receiver, the measurements allow us to distinguish between the end-to-end behavior due to the different directions of the Internet paths, which often exhibit asymmetries. We: (1) characterize the prevalence of unusual network events such as out-of-order delivery and packet replication; (2) discuss a robust receiver-based algorithm for estimating “bottleneck bandwidth” that addresses deficiencies discovered in techniques based on “packet pair;” (3) investigate patterns of packet loss, finding that loss events are not well modeled as independent and, furthermore, that the distribution of the duration of loss events exhibits infinite variance; and (4) analyze variations in packet transit delays as indicators of congestion periods, finding that congestion periods also span a wide range of time scales  相似文献   

16.
Most of the schemes that were proposed to improve the performance of transmission control protocol (TCP) over mobile ad hoc networks (MANETs) are based on a feedback from the network, which can be expensive (require extra bandwidth) and unreliable. Moreover, most of these schemes consider only one cause of packet loss. They also resume operation based on the same stand-by parameters that might vary in the new route. Therefore, we propose two techniques for improving the performance of TCP over MANETs. The first one, called TCP with packet recycling (TCP-PR), allows the nodes to recycle the packets instead of dropping them after reaching the retransmission limit at the MAC layer. In the second technique, which is called TCP with adaptive delay window (TCP-ADW), the receiver delays sending TCP ACK for a certain time that is dynamically changed according to the congestion window and the trip time of the received packet. TCP-PR and TCP-ADW are simple, easy to implement, do not require network feedback, compatible with the standard TCP, and do not require distinguishing between the causes of packet loss. Our thorough simulations show that the integration of our two techniques improves the performance of TCP over MANETs.  相似文献   

17.
The BLUE active queue management algorithms   总被引:6,自引:0,他引:6  
In order to stem the increasing packet loss rates caused by an exponential increase in network traffic, the IETF has been considering the deployment of active queue management techniques such as RED (random early detection) (see Floyd, S. and Jacobson, V., IEEE/ACM Trans. Networking, vol.1, p.397-413, 1993). While active queue management can potentially reduce packet loss rates in the Internet, we show that current techniques are ineffective in preventing high loss rates. The inherent problem with these algorithms is that they use queue lengths as the indicator of the severity of congestion. In light of this observation, a fundamentally different active queue management algorithm, called BLUE, is proposed, implemented and evaluated. BLUE uses packet loss and link idle events to manage congestion. Using both simulation and controlled experiments, BLUE is shown to perform significantly better than RED, both in terms of packet loss rates and buffer size requirements in the network. As an extension to BLUE, a novel technique based on Bloom filters (see Bloom, B., Commun. ACM, vol.13, no.7, p.422-6, 1970) is described for enforcing fairness among a large number of flows. In particular, we propose and evaluate stochastic fair BLUE (SFB), a queue management algorithm which can identify and rate-limit nonresponsive flows using a very small amount of state information.  相似文献   

18.
In this paper, we discuss different signaling techniques for optical burst-switched networks. We develop a generalized signaling framework for optical burst-switched networks, which provides guidelines about the performance of each signaling technique based on the different parameters in the framework. The two commonly used signaling techniques in optical burst switching are two-way based tell-and-wait (TAW) and one-way based just-enough-time (JET). TAW suffers from high end-to-end packet delay, while JET suffers from high packet loss. There is no signaling technique that offers flexibility in terms of both loss and delay. We propose a hybrid signaling technique called intermediate-node-initiated (INI) signaling for optical burst-switched networks. INI can provide different levels of loss and delay characteristics based on end-user application requirements. The granularity of INI ranges between the one-way based and the two-way based signaling techniques. In INI reservation of channels is initiated at an intermediate node, known as the initiating node, in both forward and backward directions at the same time. We show that by appropriately selecting the initiating node, we can simulate both TAW and JET using the INI signaling technique. Through simulations, we shown that INI performs better than TAW in terms of average end-to-end packet delay and better than JET in terms of burst loss probability. We extend the INI signaling technique to provide QoS differentiation in the OBS core, differentiated INI (DINI), by carefully choosing different initiation nodes depending on delay and loss requirements of end-user applications. Through extensive simulations, we show that the DINI technique outperforms the existing offset-based QoS technique.  相似文献   

19.
范英磊  苏放  李勇  徐惠民 《无线电工程》2007,37(10):44-46,49
无线视频传输中误码和丢包会导致视频质量的严重下降,研究了视频传输中的错误控制相关技术。对已有的无线视频错误控制方法进行了详细分析,在此基础上提出了一种更加有效的无线视频传输中的错误控制框架。将无线误码丢包和拥塞丢包准确区分,改进了以往算法带宽估计公式不准确的问题。并且对视频内容根据在解码端重要性的不同区分保护。在错误控制的同时进行了拥塞控制。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号