基于PXA255的VoIP嵌入式终端的研究与实现
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。
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.
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。
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.
引文
[1] 舒华英，赖平漳，区锐著．IP电话原理技术应用．北京：人民邮电出版社，2000．25，245，391
[2] 杨昆，薛宁等．IP电话及其增值业务技术．北京：人民邮电出版社，2002，23-46
[3] ITU-T. ITU-T Recommendation H. 323, Packet Based Multimedia Communications Systems. 1998
[4] Uyless Black著，温斌等译．VoIP：IP语音技术．北京：机械工业出版社，2000．
[5] B. Goole. Voice over Internet protocol (VoIP). Proceedings of the IEEE, 2002. 90(9): 1495—1517
[6] 何宝宏．VoIP技术发展新动态．世界电信，2005(11)：35~39
[7] 贾铸．IP电话终端的发展及设计．电声技术，2002，6：58~61
[8] 桑柿编著．嵌入式系统原理及应用开发技术．北京：北京航空航天大学出版社，2002．4
[9] 沈文斌．嵌入式硬件系统设计与开发实例详解．北京：电子工业出版社，2005
[10] 孙天泽著．嵌入式设计及Linux驱动开发指南．北京：电子工业出版社，2005
[11] 詹荣开．嵌入式BootLoader技术内幕．http://linuxsir.zahui.net/html/34/107039.htm, 2003-12.
[12] 王京起等．嵌入式可配置实时操作系统eCos技术及其实现机制．北京：电子工业出版社，2005
[13] 李善平，刘文峰等，Linux与嵌入式系统．北京：清华大学出版社，2003
[14] 陈俊宏著．Embedded Linux嵌入式系统原理与实务．北京：铁道出版社，2004．
[15] ARubini著，Lisoleg译．LINUX设备驱动程序．北京：中国电力出版社，2000
[16] 陈莉君．深入分析Linux内核源代码．人民邮电出版社，2002．447~459
[17] Daniel Colins著，舒华英等译．VoIp技术与应用．北京：人民邮电出版社．2003
[18] Wei Yu, Sriram Chellappan. P2P/Grid-based overlay architecture to support VoIP services in large-scale IP networks. Future Generation Computer Systems 21, 2005, 209-219
[19] H. Schulzrinne etal. "Signaling for Internet Telephony". Feb. 1998.
[20] RFC3261 SIP: Session Initiation Protocol. 2002. 6.
[21] Call Signaling Protocol and media stream packetization for packet-Based Multimedia Communications System. Recommendation H. 225, ITU, 1988
[22] Control protocol for Multimedia Communications, Recommendation H. 245, ITU, 1988
[23] ITU-T Recommendation Q. 931, ISDN user-network interface layer 3 specification for basic call control, May 1998.
[24] 罗斯青．H．323和SIP的比较．通讯世界．2002，8(5)：60~62
[25] Ge Zhang, Markus Hillenbrand, Paul Muller. Facilitating the Interoperability among Different VoIP Protocols with VoIP Web Services. IEEE CS Press, 2000
[26] Hannu Savolainen. Open Sound System Programmer' s Guide [EB/OL]. http://www.opensound.com/pguide/oss.pdf, 2002.13~18
[27] Dave Phillips. A User's Guide to ALSA.
[28] 杨行峻，迟惠生等．语音信号数字处理．北京：电子工业出版社，1995
[29] 鲍长春著．低比特率数字语音编码基础．北京：北京工业大学出版社，2001
[30] A. Barberis, C. Casetti. A simulation study of adapive voice communications on IP networks. Computer Communication 24, 2001,757-767
[31] Adolfo Rodriguez著，杨铁男译．TCP／IP权威教程(第七版)．北京：清华大学出版社．2002
[32] Xiaotang Zhang, Henning Schulzrinne. Voice over TCP and UDP, Columbia University Department of Computer Science, Technical Report CUCS-033-04, September 2004
[33] W．RICHARD STEVENS．UNIX网络编程．北京：清华大学出版社，2005．
[34] H. Schulzrinne, etal. RTP: A Transport Protocol for Real-Time Applications, RFC 1889, January 1996.
[35] H. Schulzrinne, S. Casner, "RTP Profile for Audio and Video Conferences with Minimal Control", RFC 3551, July 2003
[36] Liren Zhang, Li Zheng, Koh Sop Ngee. effect of delay and delay jitter on voice/video over IP. Computer Communication 25, 2002, 863-873
[37] 王仁明，唐正军等．PC—PC实时IP语音服务技术研究．西安第二炮兵工程学院，2002
[38] 熊光安，张德运．基于H.323的VoIP系统QoS实现研究．微电子学和计算机，2004，21：51～55．
[39] 陈明义，钱敏，谭勇．一种提高IP电话QoS的综合去抖动同步策略研究．计算机工程与设计．2006
[40] Xsteam(中国)软件技术有限公司．Qt程序设计．清华大学出版社，2002
[41] QT/Embedded. http://www.trolltech.com/product
[42] Y. E. Fine. Cross-platform Qt-based implementation of low level GUI layer of ROOT. Nuclear Instruments and Methods in Physics Research A 502, 2003, 681-683
[43] 倪继利．Qt及Linux操作系统窗口设计。北京：电子工业出版社，2006
[44] 毛德操，胡希明，嵌入式系统采用公开源代码和Strong ARM／XScale处理器．杭州：浙江大学出版社，2005．
[45] 马忠梅等，ARM嵌入式处理器结构与应用基础，北京航空航天大学出版社，2002．
[46] Intel公司．PXA255 Processor Developer' s Manual. pdf
[47] 陈章龙等．嵌入式技术与系统—Intel XScale结构与开发．北京：北京航空航天大学出版社，2004
[48] SDRAM datasheet, K4S561632C. pdf, http://www.21ic.com.
[49] E28F128J3A datasheet, Intel Corp.,2001
[50] A/D datasheet, ads7846, pdf, http://www.21ic.com.
[51] LAN91C96 datasheet, SMSC Corp., 2001
[52] CS4201 datasheet, CIRRUS LOGIC Corp., 2002
[53] Eve Edelson. Voice over IP security pitfalls. Network Security, February 2005, Volume 2005, Issue 2: Pages 4~7
[54] 柏银．MD5算法及其在远程身份认证中的应用．四川大学学报，2006，02
[55] 黎宝华，王妹，庞丽萍．Linux核心调度机制的实时性分析．小型微型计算机系统，1998，2：73-77
[56] Michael Barr．C／C++嵌入式系统编程．北京：中国电力出版社，2001
[57] International Telecommunications Union, Coding of speech at8kbit/susing conjugate-structure algebraic-code-excited linearprediction(CS-ACELP), Recommendation G. 729, ITU-T, March 1996.
[58] J. C. Bolot, AV Garcia. Control mechanisms for packet audio in the Internet, Proceedingsof the IEEE Infocom, 1996, 232-239
[59] Tadeus Uhl. Quality of Service in VoIP Communication. Int. J. Electron. Commun 58, 2004, 178-182
[60] Soon_Choul Kim, Jae-Hong Ryu, Won Ryu. Design of Integrated Gateway Systm's Configuration for Wireless-Internet Service in cdma2000 and W-CDMA. IEEE CS Press, 2003
[2] 杨昆，薛宁等．IP电话及其增值业务技术．北京：人民邮电出版社，2002，23-46
[3] ITU-T. ITU-T Recommendation H. 323, Packet Based Multimedia Communications Systems. 1998
[4] Uyless Black著，温斌等译．VoIP：IP语音技术．北京：机械工业出版社，2000．
[5] B. Goole. Voice over Internet protocol (VoIP). Proceedings of the IEEE, 2002. 90(9): 1495—1517
[6] 何宝宏．VoIP技术发展新动态．世界电信，2005(11)：35~39
[7] 贾铸．IP电话终端的发展及设计．电声技术，2002，6：58~61
[8] 桑柿编著．嵌入式系统原理及应用开发技术．北京：北京航空航天大学出版社，2002．4
[9] 沈文斌．嵌入式硬件系统设计与开发实例详解．北京：电子工业出版社，2005
[10] 孙天泽著．嵌入式设计及Linux驱动开发指南．北京：电子工业出版社，2005
[11] 詹荣开．嵌入式BootLoader技术内幕．http://linuxsir.zahui.net/html/34/107039.htm, 2003-12.
[12] 王京起等．嵌入式可配置实时操作系统eCos技术及其实现机制．北京：电子工业出版社，2005
[13] 李善平，刘文峰等，Linux与嵌入式系统．北京：清华大学出版社，2003
[14] 陈俊宏著．Embedded Linux嵌入式系统原理与实务．北京：铁道出版社，2004．
[15] ARubini著，Lisoleg译．LINUX设备驱动程序．北京：中国电力出版社，2000
[16] 陈莉君．深入分析Linux内核源代码．人民邮电出版社，2002．447~459
[17] Daniel Colins著，舒华英等译．VoIp技术与应用．北京：人民邮电出版社．2003
[18] Wei Yu, Sriram Chellappan. P2P/Grid-based overlay architecture to support VoIP services in large-scale IP networks. Future Generation Computer Systems 21, 2005, 209-219
[19] H. Schulzrinne etal. "Signaling for Internet Telephony". Feb. 1998.
[20] RFC3261 SIP: Session Initiation Protocol. 2002. 6.
[21] Call Signaling Protocol and media stream packetization for packet-Based Multimedia Communications System. Recommendation H. 225, ITU, 1988
[22] Control protocol for Multimedia Communications, Recommendation H. 245, ITU, 1988
[23] ITU-T Recommendation Q. 931, ISDN user-network interface layer 3 specification for basic call control, May 1998.
[24] 罗斯青．H．323和SIP的比较．通讯世界．2002，8(5)：60~62
[25] Ge Zhang, Markus Hillenbrand, Paul Muller. Facilitating the Interoperability among Different VoIP Protocols with VoIP Web Services. IEEE CS Press, 2000
[26] Hannu Savolainen. Open Sound System Programmer' s Guide [EB/OL]. http://www.opensound.com/pguide/oss.pdf, 2002.13~18
[27] Dave Phillips. A User's Guide to ALSA.
[28] 杨行峻，迟惠生等．语音信号数字处理．北京：电子工业出版社，1995
[29] 鲍长春著．低比特率数字语音编码基础．北京：北京工业大学出版社，2001
[30] A. Barberis, C. Casetti. A simulation study of adapive voice communications on IP networks. Computer Communication 24, 2001,757-767
[31] Adolfo Rodriguez著，杨铁男译．TCP／IP权威教程(第七版)．北京：清华大学出版社．2002
[32] Xiaotang Zhang, Henning Schulzrinne. Voice over TCP and UDP, Columbia University Department of Computer Science, Technical Report CUCS-033-04, September 2004
[33] W．RICHARD STEVENS．UNIX网络编程．北京：清华大学出版社，2005．
[34] H. Schulzrinne, etal. RTP: A Transport Protocol for Real-Time Applications, RFC 1889, January 1996.
[35] H. Schulzrinne, S. Casner, "RTP Profile for Audio and Video Conferences with Minimal Control", RFC 3551, July 2003
[36] Liren Zhang, Li Zheng, Koh Sop Ngee. effect of delay and delay jitter on voice/video over IP. Computer Communication 25, 2002, 863-873
[37] 王仁明，唐正军等．PC—PC实时IP语音服务技术研究．西安第二炮兵工程学院，2002
[38] 熊光安，张德运．基于H.323的VoIP系统QoS实现研究．微电子学和计算机，2004，21：51～55．
[39] 陈明义，钱敏，谭勇．一种提高IP电话QoS的综合去抖动同步策略研究．计算机工程与设计．2006
[40] Xsteam(中国)软件技术有限公司．Qt程序设计．清华大学出版社，2002
[41] QT/Embedded. http://www.trolltech.com/product
[42] Y. E. Fine. Cross-platform Qt-based implementation of low level GUI layer of ROOT. Nuclear Instruments and Methods in Physics Research A 502, 2003, 681-683
[43] 倪继利．Qt及Linux操作系统窗口设计。北京：电子工业出版社，2006
[44] 毛德操，胡希明，嵌入式系统采用公开源代码和Strong ARM／XScale处理器．杭州：浙江大学出版社，2005．
[45] 马忠梅等，ARM嵌入式处理器结构与应用基础，北京航空航天大学出版社，2002．
[46] Intel公司．PXA255 Processor Developer' s Manual. pdf
[47] 陈章龙等．嵌入式技术与系统—Intel XScale结构与开发．北京：北京航空航天大学出版社，2004
[48] SDRAM datasheet, K4S561632C. pdf, http://www.21ic.com.
[49] E28F128J3A datasheet, Intel Corp.,2001
[50] A/D datasheet, ads7846, pdf, http://www.21ic.com.
[51] LAN91C96 datasheet, SMSC Corp., 2001
[52] CS4201 datasheet, CIRRUS LOGIC Corp., 2002
[53] Eve Edelson. Voice over IP security pitfalls. Network Security, February 2005, Volume 2005, Issue 2: Pages 4~7
[54] 柏银．MD5算法及其在远程身份认证中的应用．四川大学学报，2006，02
[55] 黎宝华，王妹，庞丽萍．Linux核心调度机制的实时性分析．小型微型计算机系统，1998，2：73-77
[56] Michael Barr．C／C++嵌入式系统编程．北京：中国电力出版社，2001
[57] International Telecommunications Union, Coding of speech at8kbit/susing conjugate-structure algebraic-code-excited linearprediction(CS-ACELP), Recommendation G. 729, ITU-T, March 1996.
[58] J. C. Bolot, AV Garcia. Control mechanisms for packet audio in the Internet, Proceedingsof the IEEE Infocom, 1996, 232-239
[59] Tadeus Uhl. Quality of Service in VoIP Communication. Int. J. Electron. Commun 58, 2004, 178-182
[60] Soon_Choul Kim, Jae-Hong Ryu, Won Ryu. Design of Integrated Gateway Systm's Configuration for Wireless-Internet Service in cdma2000 and W-CDMA. IEEE CS Press, 2003