Î Pa ½ç xpa;gç Å é. n"þ Pa;Gç 3G GSM ;GÙ Pa ½ç zïp é ç é, SIP, ENUM, MPEG-4

Transcription

1

2 `Š O¼ ãypa;gç Ý~Ms" A3GC802.11Pa ½ç Þ -$"> P X3Ýçjç ]Dã0WË 3Gf R¼ Pa ½ç Ý8T3y {ÝFí> 3GÝFí> 4Q {¾2Íy Pa ½ç Q { ¾54Íy0 - Í ŠÝ.ôÎ µb T༠Pa ½ç P èºý ͱWÍÝŠX]n ÉAVoIPµÎ Ít Ý» &Æ*GSMó PaW^é Ù PaIP é ÙÝ ) ÞÎμW^s"Ýxø &Æ T:ÕμÝW^ Þ Ìn802.11C3GÝ vèqawíc Š óct Ý;Gç?È3!ç Š 6ð.hŒŒiêÝ Ç3yGPPa;Gç Å LÍ Î Pa ½ç xpa;gç Å é n"þ Pa;Gç 3G GSM ;GÙ Pa ½ç zïp é ç é, SIP, ENUM, MPEG-4 i

3 Abstract In recent years, advances in wireless communications networks such as 3G and WLAN is making the dream of fast, easy, and ubiquitous Internet access a reality. One of the advantages of WLAN over 3G is obviously its high data rate. Whereas 3G supports data rate up to 2Mbps, WLAN supports data rate up to 54Mbps. Another important factor is that for some applications, WLAN provides a much more cost effective solution. One good example is VoIP. We strongly believe that the integration of GSM digital wireless cellular phone system and wireless IP phone system will be a mainstream for the future development of cellular devices. We expect to see cellular devices having and 3G capability, being able to connect to the best network system in terms of the cost and bandwidth, and being able to switch seamlessly from one to the other whenever possible. The purpose of this project is thus to advance the state-of-the-art in mobile audio/video phone over wireless communications networks, particularly WLAN. Key words: wireless communications network, 3G, , GSM, WLAN, cellular phone, IP phone, SIP, ENUM, MPEG-4 ii

4 1 Introduction In recent years, advances in wireless communications networks have led to rapid growth in the use of cellular devices for the communication of messages and data. Thus, hand-held and other portable computing devices are in common use for information access, including , stock market data, web access, and other enterprise-critical information. The advances in wireless communications networks have also created new distribution channels and business opportunities for the dissemination of multimedia contents. Streaming audio and video over wireless communications networks is becoming a reality, and it is likely that streaming media will become a mainstream means of communication. Despite some success, streaming media still faces challenging technical issues, including quality of service and cost effectiveness. At present, there are three main communication infrastructures: the Internet, the fixed telecommunication network, and the mobile telecommunication network. The future trend of the telecommunication networks seems to favor the All-IP network for the mobile telecommunication network and IPv6 [1, 2, 3, 4, 5] for the Internet. The marriage between IPv6 and WLAN seems to be a perfect match. One of the interesting applications it provides is certainly the emerging IPv6-based Telephony System, or so called VoIP. The integration of SIP (Session Initiation Protocol) [6] and ENUM (telephone NUmber Mapping) [7] is now considered as the key enabling technology for applications such as Voice over IP, Video over IP, and Multimedia Messages and facilities such as IP Phone, SIP Proxy, Media Server, Softswitch, and IP-PBX. SIP is an application-layer control protocol that can be used to establish, modify, and terminate multimedia sessions or calls. These multimedia sessions include invitations to both unicast and multicast conferences and Internet telephony applications. SIP can be used in conjunction with other call setup and signaling protocols. SIP [6] is perhaps one of the most important communication protocols in addition to TCP/IP [8, 9] and HTTP [10]. ENUM is a mechanism to translate an E.164 Number into a list of URI with associated services. It uses the Domain Name System (DNS) for storage of E.164 numbers. Through transformation of E.164 numbers into DNS names and the use of existing DNS services, one can identify available services connected to a particular E.164 number. On the other hand, the explosion of WLAN in recent years has created the opportunities to make fast, easy, and ubiquitous Internet access a reality. It has also created the opportunities to overcome the challenging technical issues for streaming audio and video over the Internet. One of the advantages of WLAN over 3G is obviously its high data rate. Whereas 3G supports data rate up to 2Mbps, WLAN supports data rate up to 54Mbps. Another important factor is that for some applications, WLAN provides a much more cost effective solution. One good example is VoIP. The WLAN protocols [11, 12, 13, 14] specify both the physical layer and the lower half of the data link layer (i.e., the MAC sublayer) of the ISO OSI reference model. A stated goal of the initial IEEE effort was to create a set of standards which could use different approaches to the physical layer using different frequencies, encoding methods, and so forth and yet share the same higher layers. They have succeeded, and the Media Access Control (MAC) layers of the a WLAN and b WLAN protocols are substantially identical. At the higher layer, all WLAN protocols specify the use of the protocol for the logical link control (LLC) portion of the data link layer. In the ISO OSI reference model, protocols such as TCP/IP, IPX, NetBEUI, and AppleTalk exist at still higher layers and utilize the 1

5 services of the layers underneath. Given all the technologies and the deployment of Taiwan SIP/ENUM Trial Environment, one interesting application we expect to see is multimedia streaming over wireless networks, often referred to as mobile multimedia streaming, which allows multimedia contents to be accessed regardless of time and location. MPEG-4 [15, 16, 17, 18, 19, 20, 21] seems to be the choice of multimedia streaming standard for wireless devices. In offering a scalable and secure open standard for wireless and broadband networks, MPEG-4 will make mobile multimedia streaming to become a reality. Another interesting application is VoIP. VoIP is a rapidly emerging technology for voice communication that uses the IP-based networks to deploy VoIP-enabled devices in office and home environments. VoIP-enabled devices such as desktops, notebooks, and PDAs decrease the cost of voice communication, enhance existing features, and add new telephony services. VoIP using the IP-based networks also provides the opportunity to improve the quality of video phone using the telephony network. Device manufacturers and network operators develop many types of VoIP-enabled devices such as desktop phones, PDAs, and cellular phones. End users can choose from a broad variety of form factors, feature sets, and user interfaces. Except cellular phones and PDAs, one of the major problems with these VoIP-enabled devices is obviously its portability. This may keep end users from using the services. In line with the deployment of Taiwan SIP/ENUM Trial Environment, the purpose of this project is thus to advance the state-of-the-art in mobile audio/video technology over wireless communications networks, particularly WLAN. Our focus will be on the development of SIP phone based on Linux and on the feasibility study for using SIP to support multimedia streaming. Our long-term goal is much more than that and is aimed at developing an SoC-based hardware/software platform that carries not only voice, but also video with quality much superior than toady s video phone, that combines the functionality of a cellular phone and a VoIP-enabled phone, that allows end users to dynamically switch back and forth between the WLAN and the GSM digital cellular phone network, and that is comparable in size to a cellular phone. Another goal of this project is to provide a robust and flexible operating system support for the development of the hardware/software platform for the SIP phone based on Linux. We strongly believe that tomorrow s phones will be more than just phones. The integration of GSM digital wireless cellular phone system and wireless IP phone system will be a mainstream for the future development of cellular devices. Third-generation mobile technology (3G) will have to work in harmony with WLAN technology rather than compete with it for how different wireless technologies can fit together may be a threat to 3G in static locations, but there is no contest when mobility is required. 3G mobile technology provides high mobility but limited bandwidth whereas WLAN provides high bandwidth but limited mobility. We expect to see cellular devices having and 3G capability, being able to connect to the best network system in terms of the cost and bandwidth, and being able to switch seamlessly from one to the other whenever possible. We choose Linux because our long-term goal is to develop an SoC-based SIP phone that would support not only Voice over IP, but also Video over IP. And in recent years, Linux [22] has been widely used as an embedded operating system in the embedded system design. One reason is that Linux is not wedded to just one CPU architecture. Another is that Linux is highly reliable, scalable, modular, and flexible, which makes it well suited to the extreme diversity of embedded systems. Then, there is the fact that Linux is 2

6 open-source, so it is much easier to get your embedded widget to act like it is supposed to. Also, Linux s zero royalty model makes all this great stuff affordable, even in the simplest devices. More important from our viewpoint is that even though the target environment is often dissimilar to the host on which the development is conducted, Linux does not preclude us from using its multiarchitecture advantage to test our target s applications on our host with little or no modification. Though not all applications can be tested in this way, testing target applications on the host will generally save us a lot of time. As [23] reported, since 1999, use of embedded Linux has gone from zero adoption to taking second place, in terms of market share, behind Wind River. Experts estimate that embedded Linux will take over the number-one market share position by the end of Although this is probably not true, it is at least very close to. [24] reported that in terms of developer use for future projects, 30.2% of embedded developers expect to use Linux in their next embedded project, while 30.6% say they will use Windows Embedded operating systems. However, Embedded Linux has nearly double the growth rate. 2 Methods As stated in the proposal of this project, our focus in this project is mainly on the audio. Furthermore, since next-generation wireless networks are moving towards IP-based, our goal is to use Ethernet for the testing of our design and implementation. The project was divided into three phases as given below. Phase 1: Preparation (4 months) The main tasks include: Studying the protocols that are required for the implementation of the mobile audio/video phone, including , IPv6, SIP, ENUM, etc. Understanding how the SIP phone client provided by the Taiwan SIP/ENUM Trial Project, which runs on Windows, interfaces with the server by analyzing the packets being sent between the client and the server. Understanding how the voice is coded and decoded. Phase 2: Design and Implementation of a prototype SIP phone on a workstation running Linux (4 months) The main tasks include: Implementing the required client on a workstation running Linux. Testing the client against the server of the Taiwan SIP/ENUM Trial Project to ensure that they work properly. Phase 3: Porting the prototype SIP phone from the workstation to ARM-based Pre-SOC development platform (4 months) The main tasks include: Porting the prototype SIP phone to ARM-based Pre-SOC development platform. 3

7 Modifying the Linux kernel, if necessary, to support the SIP phone, in particular the device drivers to support encoding/decoding of voice. Fine tuning the performance of the client. 3 Results As stated in the proposal of this project, except a one-semester course in Linux Device Drivers [25] and a one-semester course in Advanced Network Programming covering UNIX Network Programming [26, 27, 28, 29, 30, 31], most of the students involved in this project have never had any experience on this particular area. Although we didn t get to the point of having a full implementation of the SIP phone, we did end up with three Master s theses, each of which is focused on a particular area and is required in the implementation of the SIP phone except the third thesis to be described below. The first thesis is entitled Advanced Linux Sound Architecture for Embedded Systems, which is focused on the porting of ALSA to the ARM920T-S3C2410 evaluation board, including both the ALSA driver and the ALSA library. This can be considered as the foundation for the playback and recording of the audio. We have also successfully ported a few applications that rely on ALSA to perform their tasks, which include a PCM recorder, a PCM player, and a MP3 player, to show that the foundation eventually works. The second thesis is entitled Performance Evaluation of IPsec on Embedded Systems, which is focused on the performance evaluation of the IPsec on the ARM920T-S3C2410 evaluation board. As far as this part of the project is concerned, we have successfully ported Openswan an open source implementation of IPsec for the Linux operating systems to the ARM920T-S3C2410 evaluation board and used it to set up a Virtual Private Network (VPN) tunnel between a PC and the abovementioned platform and to conduct a performance analysis based on various encryption and authentication algorithms and services provided by the IPsec. The third thesis is entitled H.264/AVC and Object-Based Coding, which probably has nothing to the audio. Instead, it is a trial project to see if object-based coding can be used to further reduce the bit-rate for H.264/AVC based coding. 4 Conclusion As we stated earlier, although we did not get to the point of a full implementation of the SIP phone, we did end up with three Master s theses. The first is focused on the ALSA driver and library, the foundation for the playback and recording of the audio. The second is focused on the IPsec, particularly the performance of IPsec on embedded systems. Though it has nothing to do with the audio, the thrid can be considered as a trial project to see if object-based coding can be used to further reduce the bit-rate for H.264/AVC based coding. 4

8 References [1] S. Deering and R. Hinden, Internet Protocol, Version 6 (IPv6) Specification, RFC 2460, Dec [2] A. Conta and S. Deering, Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification, RFC 2463, Dec [3] S. Kent and R. Atkinson, Security Architecture for the Internet Protocol, RFC 2401, Nov [4] S. Kent and R. Atkinson, IP Authentication Header, RFC 2402, Nov [5] S. Kent and R. Atkinson, IP Encapsulating Security Payload (ESP), RFC 2406, Nov [6] J. Rosenberg, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, H. Schulzrinne, and E. Schooler, Session Initiation Protocol (SIP), RFC 3261, Jun [7] P. Faltstrom, E.164 number and DNS, RFC 2916, Sep [8] J. Poster (Editor), Transmission Control Protocol, RFC 793, Sep [9] J. Postel (Editor), Internet Protocol, RFC 791, Sep [10] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, and T. Berners-Lee, Hypertext Transfer Protocol HTTP/1.1, RFC 2616, Jun [11] IEEE , 1999 Edition, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, ANSI/IEEE Std , 1999 Edition, [12] IEEE a-1999, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications High-speed Physical Layer in the 5 GHz Band, IEEE Std a-1999 (ISO/IEC :1999/Amd 1:2000(E)), [13] IEEE b-1999, Wireless LAN MAC and PHY Specifications: Higher speed Physical Layer (PHY) extension in the 2.4 GHz Band, IEEE Std b-1999 (Supplement to ANSI/IEEE Std , 1999 Edition), [14] IEEE b-1999/Cor1-2001, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Higher-speed Physical Layer (PHY) Extension in the 2.4 GHz Band Corrigendum 1, IEEE Std b-1999/Cor (Corrigendum to IEEE Std b-1999), [15] ISO/IEC :1999, Information technology Coding of audio-visual objects Part 1: Systems, ISO/IEC, [16] ISO/IEC :1999, Information technology Coding of audio-visual objects Part 2: Visual, ISO/IEC, [17] ISO/IEC :1999/Cor.1:2000, Information technology Coding of audio-visual objects Part 2: Visual, Technical corrigendum 1, ISO/IEC,

9 [18] ISO/IEC :1999/Amd.1:2000, Information technology Coding of audio-visual objects Part 2: Visual, Amendment 1: Visual extensions, ISO/IEC, [19] ISO/IEC :1999, Information technology Coding of audio-visual objects Part 3: Audio, ISO/IEC, [20] ISO/IEC :1999/Amd.1:2000, Information technology Coding of audio-visual objects Part 3: Audio, Amendment 1: Audio extensions, ISO/IEC, [21] ISO/IEC :2000, Information technology Coding of audio-visual objects Part 6: Delivery Multimedia Integration Framework (DMIF), ISO/IEC, [22] J. O gorman, Operating Systems with Linux. New York, New York: Palgrave, [23] C. Hallabaugh, Embedded Linux: Hardware, Software, and Interfacing. New York, New York: Addison Wesley, [24] R. Lehrbaum, Linux, Windows Neck-and-neck in Embedded, Embedded Systems Developer Survey, vol. 2, [25] A. Rubini and J. Corbet, Linux Device Drivers. Sebastopol, California: O reilly, Second ed., [26] W. Stevens, Advanced Programming in the UNIX Environment. New York, New York: Addison- Wesley, [27] W. Stevens, UNIX Network Programming, Volume 1: Networking APIs: Sockets and XTI. Upper Saddle River, New Jersey: Prentice Hall, Second ed., [28] W. Stevens, UNIX Network Programming, Volume 2: Interprocess Communications. Upper Saddle River, New Jersey: Prentice Hall, Second ed., [29] W. Stevens, TCP/IP Illustrated, Volume 1: The Protocols. New York, New York: Addison-Wesley, [30] W. Stevens, TCP/IP Illustrated, Volume 2: The Implementation. New York, New York: Addison- Wesley, [31] W. Stevens, TCP/IP Illustrated, Volume 3: TCP for Transactions, HTTP, NNTP, and the UNIX Domain Protocols. New York, New York: Addison-Wesley,