Video telephony is 3G's chief differentiator, its signature service. Delivering high-quality video is crucial and is generally not done in many 3G networks when they launch. The number-one complaint operators receive has to do with video quality. Commonly referenced problems with mobile video include jerky video, sync problems between video and audio, poor lip synchronization, inability to deal with fast-moving images, blank picture transmission, long times required to establish video calls, unavailability in some places, and enormous battery consumption. QoS is difficult to guarantee, and there is not enough bandwidth. These problems are compounded by the fact that 3G video quality has to compete with benchmarks set by streaming video on the Internet. 3G video telephony today is a circuit-switched application using 3G-324M, a protocol based on H.324 that was adopted because the UMTS packet network wasn't ready to handle real-time full-duplex video.
Live video requires intensive use of capacity. Many 3G operators allocate 64Kbps channels for video telephony and often find that this is not enough. However, going up to 128Kbps affects overall network capacity. In addition, reducing the number of users supported in a cell increases the price of providing video telephony. Another problem that results in degraded video telephony quality is poor radio performance. Unfortunately, there is no easy fix for this: It is a matter of weighing the parameter tradeoffs for different services in each cell. A good example of maintaining balance is in the area of power control. High-quality video requires almost perfect power control, but you cannot demand too much power from the handset without significantly reducing the battery life.
Another current shortcoming of mobile video is that cellular companies have little or no experience running live video over a network, which requires serious network management. Monitoring video service is a major issue for 3G operators. Today, video management is limited to fault monitoring, but there are few, if any, mechanisms for evaluating services. Part of the problem has been lack of proper test-and-measurement equipment. The test-and-measurement community is responding with new or upgraded tools to analyze 3G video quality. New products are also addressing the network engineering part of the equation, referred to as performance engineering. Actix (www.actix.com) claims to allow engineers to squeeze more capability out of the existing network and to more accurately pinpoint trouble spots in the network.
The complexity of mobile video is going to increase when video calls go from the circuit-switched 3G-324M approach to SIP-based video calls. 3GPP adopted H.324 with a few modifications and called the new specification 3G-324M. The modifications were made mainly in codec requirements, the network interface, and call control. Among other things, interoperability will be required to enable customers with new SIP phones to call customers using the older 3G-324M handsets. The migration to SIP is now inevitable, thanks to the introduction of three new ingredients for packet-based high-quality mobile live video:
However, there remains the major issue of latency in the IP network itself. The key factor for live video is the round-trip time (RTT), which ideally should be less than 80 milliseconds. Currently, average response times range from 100 to 500 milliseconds (depending on the world region), which means that during busy times, latencies can easily be over 1,000 milliseconds. The Internet Traffic Report Web site (www.internettrafficreport.com/main.htm) contains reports on the current performance of major Internet routes around the world and includes statistics on latencies and packet loss.
The future of mobile video goes far beyond video telephony. Live video is expected to become the basis for a wide range of potential 3G revenue producers, including security camera feeds, video chat, video-enabled call centers, video sharing, and music videos. In support of these advanced services, operators need to measure not just QoS but the quality of the experience.
Part I: Communications Fundamentals
Telecommunications Technology Fundamentals
Traditional Transmission Media
Establishing Communications Channels
Part II: Data Networking and the Internet
Data Communications Basics
Local Area Networking
Wide Area Networking
The Internet and IP Infrastructures
Part III: The New Generation of Networks
Broadband Access Alternatives
Part IV: Wireless Communications
Wireless Communications Basics
WMANs, WLANs, and WPANs
Emerging Wireless Applications