Chapter 4: Multimedia Streaming Over Mobile Networks: European Perspective

Igor D.D. Curcio ^[1]

4.1 Introduction

Mobile communications, Internet connectivity, and multimedia technologies are progressively merging in a single paradigm of personal communications. Mobile communications originate from the increasing need of users to have information available "anytime, anywhere." Internet connectivity puts a huge quantity of information resources at users' disposal, including services such as searching, browsing, e-mail, and E-commerce. Multimedia technologies are emerging as users want to have more information in audio/visual form rather than in textual form.

Mobile networks have been developed in the past two decades to allow users to make phone calls in total mobility. These systems have evolved from the first generation (1G) of analog networks (such as AMPS, TACS, NMT, and NTT) in the 1980s, to the second generation (2G) of digital networks (such as GSM, PDC, D-AMPS, IS-95) in the late 1980s. Digital networks offer higher spectrum efficiency, better data services, and more-advanced roaming capabilities than the 1G systems. Furthermore, GSM has evolved to offer more-advanced services such as higher bit rates for circuit- and packet-switched data transmission. Those networks are commonly referred to as the 2.5G networks. HSCSD (High-Speed Circuit-Switched Data), GPRS (General Packet Radio Service) and EDGE (Enhanced Data rates for GSM Evolution) are extensions of the current GSM network, and allow reaching bit rates up to 64, 171.2, and 473.6 kbps, respectively. The new 2.5G networks are able to carry low and medium bit rate multimedia traffic, allowing the feasibility of applications requiring real-time video and audio.

A strong effort has been made by standardization bodies toward third generation (3G) networks that offer even higher bit rates (up to 2 Mbps), more flexibility, multiple simultaneous services for one user, and different quality-of-service (QoS) classes. For example, a user could establish a video streaming session or browse the World Wide Web while retrieving a file from a corporate intranet server as a background process. In the International Telecommunications Union (ITU), the 3G networks are called IMT-2000 (International Mobile Telecommunications year 2000). IMT-2000 represents the joint effort of merging the European, Asian/Japanese, and North American standards into a unique common platform for mobile communications. IMT-2000 specifications are defined by the Third Generation Partnership Project (3GPP), which has written standards for UMTS (Universal Mobile Telecommunications System) 3G networks and services since December 1998. The specifications have evolved through different releases, from Release '99, to Releases 4, 5, and 6. The different releases have been planned to enable the transition to packet-switched (PS), all-IP (Internet Protocol) mobile networks.

Recent advances in video compression technology have made possible the transmission of real-time video over low-bit-rate links. H.263 and MPEG-4 are two examples of video compression algorithms. However, the deployment of mobile video is a challenging issue. First, video processing, including compression and decompression, is CPU intensive; this and the constraints of a mobile device mean that the digital signal processing (DSP) platform must be of limited size and weight, but still capable of processing a large quantity of data, possibly in real-time. Second, efficient error-resilience techniques must be developed in order to recover from bit errors and packet losses inherently present in the air interface during data transmission.

A typical video application is multimedia streaming, which has been widely deployed over the Internet for many years. Mobile multimedia streaming is enabled by the capacity of the current 2.5G or 3G networks, and by the multimedia capabilities of current and next-generation mobile phones.

This chapter is an introduction to mobile multimedia streaming. It is organized as follows: Section 4.2 describes the end-to-end architecture for mobile streaming systems. Section 4.3 includes a review of the current mobile networks that enable streaming applications, and Section 4.4 introduces the current standards for mobile streaming. Section 4.5 contains some performance and QoS considerations for streaming. Section 4.6 concludes this chapter.

^[1]The opinions expressed in this chapter are those of the author and not necessarily those of his employer.