【作者】 曾理文；

【导师】 陈明义；

【作者基本信息】 中南大学 ， 电路与系统， 2007， 硕士

【摘要】 利用Internet网络进行语音传输的VoIP(Voice over IP)技术是当前网络增值业务应用的核心技术平台。目前对VoIP技术的研究主要包括两类，一是扩展VoIP的应用范围，结合嵌入式技术的发展开发新的实现方式，如intranet，无线终端，各种VoIP终端架构和IPBX等等。另一类围绕改善现有IP电话通信质量，包括引入高性能DSP处理器，完善信令控制技术，语音实时处理技术，低速率的语音编码和安全性等。本文结合嵌入式系统和VoIP技术的发展趋势和热点，设计实现了一种VoIP系统专用嵌入式接入终端系统。本文首先设计实现了一个由PXA255微处理器、网络控制器、音频芯片，LCD和触摸屏构成的IP电话嵌入式接入终端硬件平台，构建了嵌入式Linux操作系统环境，并在此基础上设计了VoIP的客户端程序；该客户端系统参考H.323协议架构，设计实现了登陆／注册、呼叫、通话控制和系统管理等控制信令，扩展了短信息通信、用户管理等功能；终端嵌入了高效低速率语音编码算法，能有效利用网络资源；为了保障语音的实时传输和通话效果，在采用JRTP库传输语音数据的基础上，设计实现了一种自适应可变长的消抖缓冲区，提高系统语音接收处理能力和效果；研究了嵌入式图形开发技术，利用Qt／e开发出终端的用户图形界面，配合语音和信息提示，提供完善的管理控制功能，界面丰富，友好易用。本设计采用高性能微处理器，配合嵌入式Linux强大支持功能的实现方案，具有高性能、低成本、小型化、实时性强等诸多优点。相比传统的实现架构，该设计具有更好的灵活性和操作性，性价比更高，功能更强大，同时可扩展性和可移植性也更好，具有一定的技术先进性和广泛的应用前景。更多还原

【Abstract】 VoIP technology that transmit speech over internet is the core technology of new value-added services over current network. At present, the research on VoIP focus on two fields. One is developing new ways of VoIP implementation combined with embedded system and expanding the area of application, such as intranet, wireless terminal, new structure, IPBX and so on. The other is about how to improve the quality of current VoIP communication, include using high performance DSP, good control signal, real-time technology of speech, low-rote coding technology, security and so on.Considering the development direction of VoIP and the hot point of embedded system technology, this project tries to design and implement a VolP terminal. At first, the hardware of embedded terminal was designed which consist of a micro processor-PXA255, network controller, speech codec, LCD and touch screen. Then the embedded Linux system environment was build to support application software. Base on the above hardware and soft environment, the software of VoIP client was designed and implemented. Taking the protocol stack H.323 as reference, the signal that including login, registration, call, communication controller, system controller was designed and implemented. R also supports short message communication and user management. A kind of low-bit rate codec was embedded in system to economize network resource. To insure the quality of communication, a kind of adaptive signal-wobble elimination buffer was designed and implemented basing on speech signal transmitted by JRTP. At last, with the Qt/e kit, a friendly and pretty GUI was developed, which could supply perfect management of system to users.Because of the high performance of micro processor and linux, combining with optimized software, the embedded terminal owns predominance of high reliability, expansibility, transportability and low cost with high performance. It is advanced and useful in many fields.更多还原