3G Mobile TV
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Phnom Penh,
Cambodia
Friday, June 20, 2008
Mobile phones are not just for talking anymore. Today's tech-savvy consumers view their phones as an entertainment center as well as a communication device. As a result of the build-out of 3G networks that fuel mobile video use, IDC analysts expect that revenues from mobile TV and mobile video in Western Europe alone will reach nearly $2 billion by 2009.1 In fact, Yankee Group has found that as soon as consumers switch to a 3G phone, their usage of non-messaging mobile data applications, such as video, increases by 70 percent.2 This growth presents mobile operators with a ripe opportunity to deliver live TV right into the hands of their waiting subscriber base.
The presence of 3G networks is a critical element for the success of mobile interactive video because it enables the near-instant delivery of high-quality content. There are more than 100 million Wideband-Code Division Multiple Access (W-CDMA) 3G-enabled phones worldwide, the majority of which are ready for sophisticated video transmissions. In Japan alone, NTT DoCoMo already has 15 million W-CDMA subscribers and continues to grow this base.3
Where 3G networks are available, mobile TV is proving to be the "killer app" that drives consumers to make the switch to 3G. Consumers in Europe and Asia who have long considered the mobile phone a necessity now look beyond its communication ability, and it doesn't take long to convince them that a ride on the subway is more fun while watching a new music video or a live sports event than it is just making a call or checking email. Creating and deploying a mobile TV application in a carrier environment, however, can be challenging and daunting, especially if key technologies and standards are minimally supported. This paper discusses a unique way to deliver mobile TV and mobile video services using the video telephony capability available in 3G Universal Mobile Telephone System (UMTS) networks.
3G-324M and Mobile TV
Widespread compliance with the 3G-324M standard is a key ingredient in the growth of the mobile TV market. Developed under the auspices of the Third Generation Partnership Project (3GPP), 3G-324M is an umbrella standard for the delivery of real-time multimedia services over existing circuit-switched mobile networks. The 3G-324M specification provides for multiplexing of audio, video, and H.245 signaling on a 64 kbps time division multiplexing (TDM) channel. Within each channel, up to 42 kbps is allocated to video, up to 12.2 kbps to audio, and the remainder to signaling. With modern codec technology, this relatively modest bandwidth can deliver multiplexed audio, video, and control information over the same channel while delivering a remarkably satisfying user experience.
The 3G-324M standard provides multiple benefits for mobile TV deployment:
· Ubiquity -Almost all W-CDMA-based 3G handsets on the market today support the 3G-324M protocol. There is no need to wait for more handset vendors to introduce this feature or to roll out the service on only a few handsets that can support mobile TV.
· Infrastructure Costs -The 3G-324M protocol uses the existing 3G network for all audio and video. There is no need to build a costly parallel network solely for transmitting mobile TV data.
· Interactivity -The 3G-324M protocol includes a specification for sending dual-tone multi-frequency (DTMF) style information from the handset. For mobile TV, these key presses can be used to change the channel; control pause, fast forward, and rewind; as well as to provide interactive services, such as televoting. Latencies over the TDM connection are kept to a minimum, so the reaction to a user's input typically will be seen in about 0.5 seconds.
In a 3G mobile TV application, a mobile subscriber simply keys in a short access number and uses the video-calling feature of the handset to call in to the 3G mobile TV system. After the system answers the call, the user is presented with a choice of channels.
Channels are selected using the telephone keypad, and the user can change the channel whenever desired. The number of channels offered by a 3G mobile TV system is limited only by the imagination of the system developer and the availability of video content.
Channels offered by the system can be either a live channel or a virtual channel. Live channels are streamed in real time, either from traditional television channels or other live video sources, such as traffic cameras. Virtual channels are made up of a series of short video clips that are played one after another, but they appear as normal channels to the user. This format can be used for sports highlights, movie trailers, financial information, and many other types of content. Virtual channels offer the advantage of allowing the user to skip or repeat a segment simply by pressing a key on the telephone keypad.
A variety of business models are possible for 3G mobile TV, including per-minute charges, subscription-based unlimited access, and free access supported by advertisers. Special billing for premium-rate content also can be supported.
Tools Needed to Deploy 3G Mobile TV
A mobile TV application should include the following components for a fully functional system:
· 3G-324M Gateway Function , which forms a bridge between 3G-324M video calls from the mobile handset to the IP network that hosts the media components. On the 3G network side, the interface will be E1 or T1, using either Integrated Services Digital Network (ISDN) or Signal System 7 (SS7) ISDN User Part (ISUP) signaling. On the IP side, there will be separate audio and video streams, using the Real-Time Transfer Protocol (RTP) for transport.
· Video-enabled IP Media Server , which plays stored video clips across the IP network. The output of the server is separate audio and video RTP streams, which are sent to the 3G-324M gateway to deliver video to the end user's handset. The media server uses an IP interface to enable integration with stream servers (used for live video streams) and to allow for IP-based video in the future. If the IP media server has a high-level command interpreter, it can interface to the application server using a high-level language such as Voice Extensible Markup Language (VoiceXML). Otherwise, the interface to the application server could be a low-level media control protocol or direct application programming interface (API) control.
· Application Server , which implements the actual user experience of the system by controlling the IP media server component. The definitions of channels, how to react when the user presses a key, and any interactive applications are handled here.
· Content Server , which stores the video clips to be played and offers an interface for the content owners to upload their video clips. The clips are sent to the IP media server as requested by the user. The content server and application server often will be combined into one physical system. In some architectures, the content server, application server, 3G-324M gateway, and IP media server all will be combined.
· Video Transcoder , which converts a wide variety of possible video formats into one of the specific video formats that can be used for 3G-324M. This component is required when a video source is not in a format suitable for sending directly to a 3G-324M mobile handset.
· Video Stream Server , which is used to transmit a live video stream to each viewer of that stream via the 3G-324M gateway.
· Live Video Encoder , which takes audio and video signals from a locally connected microphone and camera, or from an external source, and encodes them into audio and video RTP streams. These RTP streams are then sent to the video stream server for further distribution to each user.
/NR/rdonlyres/84CAEA5E-49F0-4EA6-A0AC-2EED90F71CC2/0/MobileTVandVideo_Fig1.jpg /NR/rdonlyres/84CAEA5E-49F0-4EA6-A0AC-2EED90F71CC2/0/MobileTVandVideo_Fig1.jpg
Figure 1: 3G Mobile TV-How the Pieces Fit Together (click for larger view)
Considerations for Mobile TV Application Deployment
Video and Audio Formatting
Audio and video formatting are among the foremost considerations for a 3G-324M mobile TV deployment. In the area of formats, the 3G-324M standard offers both advantages and unique challenges versus video streamed over IP.
The primary advantage is the uniformity of mobile handset video capabilities. Because the 3G-324M specification is very precise in this aspect, all 3G-324M mobile handsets support the same audio codec, the same screen size, the same maximum frame rate, and, for the most part, the same video codecs. All 3G-324M handsets support Advanced Multi Rate (AMR) as an audio codec and H.263 as a video codec. Almost all 3G-324M handsets support MPEG-4 as an alternate video codec. This means that it is possible to use the same format to prepare all video clips and be confident that each video will be compatible with all 3G-324M handsets in the market.
The 3G-324M standard presents video-formatting challenges due to the fixed 64 kbps channel allocated for audio, video, and control. The bandwidth used by audio, control, and packet overhead depends on the audio rate used. In the worst case scenario, these consume 22 kbps, which leaves 42 kbps for video. It is very important that the video portion of the clip does not exceed this video bandwidth limitation. The same limitation applies to live streaming video and stored video clips. If the rate is exceeded, the video will be delayed over time, and, in extreme cases, the received video quality will be seriously degraded.
Because of the fixed-bandwidth nature of 3G-324M, it is also important that the video rate is steady for the duration of any clip or live stream. If the rate at the beginning of the video clip is very high but later drops, the same types of problems can be seen, even if the average video rate is kept under the limit.
Some video encoders are not well suited for 3G-324M, and video encoders that are designed for creating files to be downloaded or streamed over data networks will have large variations in video rate. Developers of a 3G mobile TV application should consider encoding their video streams using encoders specifically designed for 3G-324M compatibility, or should add a real-time video transcoder to the system to convert the video into a suitable format.
SS7 Networks
In general, a 3G mobile TV application will be deployed within the network of a 3G mobile operator. ISDN may be the desired interface for enterprise deployments of 3G-324M video equipment, but when the equipment is deployed within the 3G network, the SS7 protocol is generally the only choice. A 3G mobile TV application uses only the ISUP portions of the SS7 protocol, so with the appropriate SS7 interface, the integration should be straightforward.
3G Mobile TV on CDMA-2000 Networks
The 3G-324M specification is maintained by the 3GPP and applies only to W-CDMA-based 3G networks. The 3GPP2 organization, which maintains the CDMA-2000 specifications, has created the C.S0042 specification that defines a protocol for circuit-switched video communications over a CDMA-2000 network. The C.S0042 protocol is similar to 3G-324M, allowing for the potential to create a 3G mobile TV application for CDMA-2000-based networks. However, to date the C.S0042 specification is not supported by most CDMA-2000 handsets or networks. Therefore, until support for these protocols becomes more widespread, the 3G mobile TV application is limited to W-CMDA networks.
3G Mobile TV in an IMS World: A Look Ahead
When designing a new application for 3G mobile networks, it is important to consider how the application will function under the emerging IP Multimedia Subsystem (IMS) architecture. While it is unlikely that applications being deployed today will use IMS immediately, it will be straightforward to change to an IMS framework in the future if the system is properly designed from the start. In an IMS-based network, the current TDM interfaces will be replaced by IP, and the current SS7 signaling will be replaced by variants of Session Initiation Protocol (SIP). Although details of how video calls will be handled under IMS are still uncertain, two approaches are being pursued:
· 3G-324M over IP. In this approach, the entire 64 kbps TDM channel containing the multiplexed audio, video, and control is sent over a series of IP packets. The 3G-324M protocol continues to be used, but the transport has changed from TDM to IP. In this case, the architecture of a 3G mobile TV solution stays almost exactly the same, but a 3G-324M gateway component that enables 3G-324M over IP instead of over TDM is needed.
· Separate Audio and Video Streams over IP. In this approach, the 3G-324M protocol is no longer used by the 3G mobile TV system. The audio and video are sent over IP using separate streams. In this case, the 3G-324M gateway component is not used, and the interface to the IMS network is made directly to the video-enabled IP media server. The other components in the system are unchanged.
NMS Offering
NMS Communications offers two product families that can be used to create a 3G mobile TV system.
Vision VoiceXML Server
Vision VoiceXML Server gives application providers the ability to rapidly develop and deploy new, innovative VoiceXML-controlled voice and video applications in IP, public switched telephone network (PSTN), and 3G324M networks. The Vision VoiceXML Server is fully compliant with W3 Consortium (W3C) VoiceXML 2.0 and 2.1 specifications.
The Vision VoiceXML Server includes the 3G video gateway and video-enabled IP media server components in a single carrier-grade platform. It supports either ISDN or SS7 ISUP on the interface to the mobile network. The application server controls the Vision VoiceXML Server using industry-standard VoiceXML 2.1, which is extended to play video clips and make Real-Time Streaming Protocol (RTSP) connections to a stream server to play live video content. Figure 2 shows a typical architecture for a 3G mobile TV system using the Vision VoiceXML Server.
/NR/rdonlyres/B8F2A947-8876-428D-ABBD-8E6F352A7815/0/MobileTVandVideo_fig2.jpg /NR/rdonlyres/B8F2A947-8876-428D-ABBD-8E6F352A7815/0/MobileTVandVideo_fig2.jpg
Figure 2: 3G Mobile TV Using NMS Vision VoiceXML Server (click to view larger)
Video Access Toolkit and CG Series Boards
Video Access is the ideal development environment for meeting the demand for flexible, scalable, and cost-effective 3G mobile video solutions. Developers can rapidly implement new video solutions using the Video Access APIs in conjunction with NMS's renowned Natural Access(tm) development environment and the CG Series of Peripheral Component Interconnect (PCI) and CompactPCI (cPCI) boards.
A developer creating a 3G mobile TV system uses the Video Access 3G-324M Gateway API to create the 3G-324M gateway component, and the Video Access Messaging API to create the video-enabled IP media server component. In most cases, these functions will share the same physical system and will use a single CG board. The same system may also be used as an application server and content server, if desired. The NMS Software Video Transcoder optionally may be added to the system to ensure that both video clips and live streaming video conform to the strict video encoding requirements of the 3G-324M protocol.
Figure 3 shows a typical architecture for a 3G mobile TV system using Video Access software and CG Series hardware.
/NR/rdonlyres/499AF4F1-3061-4153-9ED4-B1D5B3AAAD89/1643/MobileTVandVideo_fig5.gif /NR/rdonlyres/499AF4F1-3061-4153-9ED4-B1D5B3AAAD89/1643/MobileTVandVideo_fig5.gif
Figure 3: 3G Mobile TV Using Video Access (click to view larger)
The rising demand for mobile video services, such as mobile TV, has created major revenue opportunities for network operators and application developers. The advent of 3G networks worldwide provides an opportunity for mobile operators to open up new revenue streams and increase subscriber adoption rates by delivering unique and innovative applications and services. Mobile TV is not a simple medium, however, and developers face stringent performance requirements, multiple interoperability issues, and a variety of other technical challenges. Fortunately, they do not have to face these challenges on their own. Advanced platforms and toolkits available from industry leaders like NMS Communications alleviate the technical complexities of mobile TV and give developers the resources they need to produce compelling and profitable applications.
[1] IDC, "Western Europe Consumer Mobile Data Applications: Forecast and Analysis, 2004-2009," November 2005.
[2] Yankee Group, "European 3G Market Gains Momentum," August 2005.
[3] 3G Today, www.3gtoday.com .
