检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

基于voip技术的甚高频电台用户终端设计

电子制作 2024年第9期32卷 50-53页

作者：万雄刘涛莫运如成都天奥信息科技有限公司四川成都611731

随着民航运输业的快速发展,甚高频电台的架设数量爆发性增长,实现电台资源共享为必然需求。voip技术是一种基于IP的话音通信技术,具有通信效果良好、运行成本低廉、可扩展性强、使用灵活性高、系统间兼容好等优势,得到了国际民航组织的... 详细信息

随着民航运输业的快速发展,甚高频电台的架设数量爆发性增长,实现电台资源共享为必然需求。voip技术是一种基于IP的话音通信技术,具有通信效果良好、运行成本低廉、可扩展性强、使用灵活性高、系统间兼容好等优势,得到了国际民航组织的大力推广。作者广泛收集用户需求后,应用voip技术,设计了一种基于voip技术的甚高频电台用户终端,完成了电台资源共享,还实现了电台参数远程设置、工作状态监视。

关键词：甚高频系统 voip 用户终端

在线全文

学校读者我要写书评

暂无评论

基于voip的空管语音交换系统

长江信息通信 2024年第6期37卷 149-151页

作者：郑青青田才艳中国民用航空飞行学院四川广汉618307

随着空管业务的复杂化,对于高效、可靠的语音通信系统的需求愈发迫切。文章研究了以voip为基础的空中交通语音交换系统,旨在探讨其在航空运营中的应用前景、优势与挑战。文章首先介绍了voip的基本原理及它相对于传统通信系统的优势。随... 详细信息

随着空管业务的复杂化,对于高效、可靠的语音通信系统的需求愈发迫切。文章研究了以voip为基础的空中交通语音交换系统,旨在探讨其在航空运营中的应用前景、优势与挑战。文章首先介绍了voip的基本原理及它相对于传统通信系统的优势。随后通过分析空中交通语音通信需求,揭示传统语音交换系统的局限性。最后引入基于voip的空管语音交换系统,阐述其系统组成和工作机制,为未来航空通信技术的发展提供新思路。

关键词： voip 空中交通语音交换系统

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

民航地空通信系统话音比选技术分析与研究

长沙航空职业技术学院学报 2024年第1期24卷 21-25页

作者：李勇中国民用航空西北地区空中交通管理局宁夏分局宁夏银川750009

对于民航地空通信中同频异址台的接收信号,我们需要采用比选技术选出信号质量最佳的一路送给管制员,从而避免多路信号叠加带来的叠音混响及由于时延不同导致的回音等问题。讨论同频异址台接收信号时的比选技术,对传统的模拟话音信号比... 详细信息

对于民航地空通信中同频异址台的接收信号,我们需要采用比选技术选出信号质量最佳的一路送给管制员,从而避免多路信号叠加带来的叠音混响及由于时延不同导致的回音等问题。讨论同频异址台接收信号时的比选技术,对传统的模拟话音信号比选技术和voip话音信号比选技术进行分析与研究,以阐述相关实现方法与技术优劣。

关键词：最佳信号选择话音信号比选 voip

基于FreeSwitch的校园智能通信系统的设计与实现

在线全文

学校读者我要写书评

暂无评论

物联网技术 2024年第2期14卷 48-51页

作者：马小青西安欧亚学院信息工程学院陕西西安710065

随着校园信息化建设的不断推进,越来越多的教育应用需要实现音视频通信,如网课、远程实验等。因此,建立一种高效、稳定、低成本的校园智能通信系统是非常必要的。本设计利用开源的FreeSwitch平台,搭建了一套多终端、多种网络环境接入、... 详细信息

随着校园信息化建设的不断推进,越来越多的教育应用需要实现音视频通信,如网课、远程实验等。因此,建立一种高效、稳定、低成本的校园智能通信系统是非常必要的。本设计利用开源的FreeSwitch平台,搭建了一套多终端、多种网络环境接入、适用于多种应用场景的联络中心系统,实现了以“校园智能语音通信平台”为支撑,以“基于开放标准SIP多终端类型提供”为基础,以“虚拟集群、园区会议、智能录音、号码携带”为基本服务内容,以教室、办公室和宿舍等师生办公生活场所为依托,建立统一的智能通信园区管理平台,打造真正意义上的“没有电话线的电话网络”。相比传统基于有线语音/数据网络的通信交换硬件系统,软件voip系统的优势体现在终端的多样性、网络的利旧性、接入方式的多样性与各种平台对接的开放性方面。

关键词： FreeSwitch voip SIP 校园智能通信系统 IVR 留言

Implementation of a Prototype voip System

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2000年第5期15卷 480-484页

作者：刘喜成李仲同 CentreforCommunicationsSystemsResearch UniversityofCambridgeUK NetworkingandComputingSystemsGroup MotorlaSemiconductorProductsSector

voip (Voice over IP) is a rapidly growing area with great market potential. To promote it for both commercial and research purposes, a prototype voip system based on state-of-the-art Motorola communication techniques has been developed. It is a gateway system integrating a PBX and a voip module. All components that H.323 defines to support voip are implemented in the voip module, though in a simplified manner. As an embedded system, the system features real timeness and task distributiveness. A number of additional techniques are used to improve the performance, including noise suppression, zero copy, and buffer structure optimization. When refined in interoperability, the system will also readily serve as a product.

关键词： voip gateway gatekeeper communication common platform embedded system voice processing H.323

Steganography in low bit-rate speech streams based on quantization index modulation controlled by keys

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2017年第10期60卷 1585-1596页

作者： HUANG YongFeng TAO HuaiZhou XIAO Bo CHANG ChinChen Department of Electronic Engineering Tsinghua University Department of Information Engineering and Computer Science Feng Chia University

Since low bit-rate speech codecs used for voice over internet protocol(voip), such as iLBC(internet low bit-rate codec), G.723.1and G.729 A, have less redundancy due to high compression, it is more challenging to embed information in low bit-rate speech streams of voip. In this study, a new method is proposed for steganography in low bit-rate speech streams of voip. The core idea of this method is setting up a graph model for the codebook space of the quantizer. Based on the graph model, the method realises a quantization index modulation(QIM)-controlled algorithm for partitioning the codebook space. It can be proved that this method can minimize signal distortion while steganography taking place. Taking into account codeword partition balance and partition diversity, the proposed steganographic algorithm was based on QIM controlled by secret keys, i.e., mapping the ways of codebook division into secret keys, thereby significantly improving the undetectability and robustness of voip steganography. Performance measurements and steganalysis experiments showed that the proposed QIM-controlled steganographic algorithm was more secure and robust than the QIM algorithm, the conventional RANDOM algorithm and the original codebook algorithm.

关键词：语音编解码器低比特率量化器调制索引 G.723.1 控制算法 voip

Survey and Analysis of voip Frame Aggregation Methods over A-MSDU IEEE 802.11n Wireless Networks

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2021年第2期66卷 1283-1300页

作者： Mosleh M.Abualhaj Abdelrahman H.Hussein Manjur Kolhar Mwaffaq Abu AlHija Al-Ahliyya Amman University AmmanJordan Prince Sattam Bin Abdulaziz University Al-KharjSaudi Arabi

The IEEE 802.11n standard has provided prominent features that greatly contribute to ubiquitous wireless networks.Over the last ten years,voice over IP(voip)has become widespread around the globe owing to its low-cost or even free call rate.The combination of these technologies(voip and wireless)has become desirable and inevitable for organizations.However,voip faces a bandwidth utilization issue when working with 802.11 wireless networks.The bandwidth utilization is inefficient on the grounds that(i)80 bytes of 802.11/RTP/UDP/IP header is appended to 10–730 bytes of voip payload and(ii)765μs waiting intervals follow each 802.11 voip frame.Without considering the quality requirements of a voip call,be including frame aggregation in the IEEE 802.11n standard has been suggested as a solution for the bandwidth utilization issue.Consequently,several aggregation methods have been proposed to handle the quality requirements of voip calls when carried over an IEEE 802.11n wireless network.In this survey,we analyze the existing aggregation methods of voip over the A-MSDU IEEE 802.11n wireless standard.The survey provides researchers with a detailed analysis of the bandwidth utilization issue concerning the A-MSDU 802.11n standard,discussion of the main approaches of frame aggregation methods and existing aggregation methods,elaboration of the impact of frame aggregation methods on network performance and voip call quality,and suggestion of new areas to be investigated in conjunction with frame aggregation.The survey contributes by offering guidelines to design an appropriate,reliable,and robust aggregation method of voip over 802.11n standard.

关键词： voip voip frame aggregation IEEE 802.11n bandwidth utilization A-MSDU A-MPDU

Audio steganography with AES for real-time covert voice over internet protocol communications

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2014年第3期57卷 76-89页

作者： TANG ShanYu JIANG YiJing ZHANG LiPing ZHOU ZhangBing School of Computer Science China University of Geosciences School of Information Engineering China University of Geosciences

As a popular real-time service on the Internet,Voice over Internet Protocol(voip)communication attracts more and more attention from the researchers in the information security field.In this study,we proposed a voip steganographic algorithm with variable embedding capacities,incorporating AES and key distribution,to realize a real-time covert voip communication.The covert communication system was implemented by embedding a secret message encrypted with symmetric cryptography AES-128 into audio signals encoded by PCM codec.At the beginning of each voip call,a symmetric session key(SK)was assigned to the receiver with a session initiation protocol-based authentication method.The secret message was encrypted and then embedded into audio packets with diferent embedding algorithms before sending them,so as to meet the realtime requirements of voip communications.For each audio packet,the embedding capacity was calculated according to the specific embedding algorithm used.The encryption and embedding processes were almost synchronized.The time cost of encryption was so short that it could be ignored.As a result of AES-based steganography,observers could not detect the hidden message using simple statistical analysis.At the receiving end,the corresponding algorithm along with the SK was employed to retrieve the original secret message from the audio signals.Performance evaluation with state-of-the-art network equipment and security tests conducted using the Mann-Whitney-Wilcoxon method indicated that the proposed steganographic algorithm is secure,efective,and robust.

关键词： voip steganography AES covert communication Mann-Whitney-Wilcoxon

Steganalysis of Low Embedding Rate CNV-QIM in Speech

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2021年第8期128卷 623-637页

作者： Wanxia Yang Miaoqi Li Beibei Zhou Yan Liu Kenan Liu Zhiyu Hu Mechanical and Electrical Engineering College Gansu Agricultural UniversityLanzhou730070China

To address the difficulty of detecting low embedding rate and high-concealment CNV-QIM(complementary neighbor vertices-quantization index modulation)steganography in low bit-rate speech codec,the code-word correlation model based on a BiLSTM(bi-directional long short-term memory)neural network is built to obtain the correlation features of the LPC codewords in speech codec in this paper.Then,softmax is used to classify and effectively detect low embedding rate CNV-QIM steganography in voip streams.The experimental results show that for speech steganography of short samples with low embedding rate,the BiLSTM method in this paper has a superior detection accuracy than state-of-the-art methods of the RNN-SM(recurrent neural network-steganalysis model)and SS-QCCN(simplest strong quantization codeword correlation network).At an embedding rate of 20%and a duration of 3 s,the detection accuracy of BiLSTM method reaches 75.7%,which is higher than that of RNNSM by 11.7%.Furthermore,the average testing time of samples(100%embedding)is 0.3 s,which shows that the method can realize real-time steganography detection of voip streams.

关键词： CNV-QIM steganography BiLSTM steganalysis voip speech