24.1 Introduction

With the advent of the twenty-first century, market forces are accelerating the pace of wireless technology evolution. It is widely anticipated that future mobile users will enjoy a near-ubiquitous access to high-bandwidth wireless networks. ^[1] Probably, mobile phone services represent the most-prominent example of widespread access to wireless communication networks. Recently, notable efforts such as i-mode ^[2] and WAP ^[3] have been carried out to exploit phone-based wireless technology along with the Internet, to provide Web services to mobile users. As of today, unfortunately, those efforts have resulted in little more than e-mail access and limited Web browsing. Although this situation is slowly improving, it is easy to envisage that old pricing schemes, along with content not suitably formatted for mobile phones, may limit the interest of mobile consumers in wireless services.

However, in parallel with the recent improvements of high-bandwidth wireless communications, the wired Internet's progress has determined a significant innovation among music distribution paradigms. The maturing distributed file-sharing technology implemented by systems like Napster has enabled the dissemination of musical content in digital form, allowing consumers to link to stored music files from around the world.

Hence, with users adopting Internet-enabled cellular phones and similar handheld devices we may expect that a growing demand may emerge for wireless services that enable mobile consumers to access music content from the large musical storehouse represented by the Web. ^[4]

In this context, the 3G UMTS technology promises to be one of the milestones in the process of building an adequate large-scale wireless infrastructure for delivering musical services to mobile consumers. Important advantages of the UMTS technology amount to the fact that packets originating from UMTS devices can be directly transmitted to IP networks (and vice versa), while specific quality of service guarantees may be provided over the wireless links. Additionally, UMTS offers higher data rates (up to a few Mbps) and an increased capacity. These data rates plus compression techniques will allow users to access HTML pages and video/audio streaming, as well as enhanced multimedia services for laptops and smaller devices. ^[5]

Nevertheless, it is well known that even with the adoption of the UMTS technology various technical communication problems may arise due to:

The time-varying characteristics of the UMTS links
Possible temporary link outages
Protocol interference between the UMTS radio link level protocols and the Internet transport protocols
Typical high bit error rates of the UMTS radio links

As a result, all the above-mentioned limitations may keep some older applications designed for music distribution over the wired Internet from working efficiently and effectively when deployed over UMTS-based mobile communications scenarios.

In this chapter, we describe a modern Internet wireless application we have designed to support the widespread delivery of musical services to Internet-enabled mobile phones and similar handheld devices over UMTS links. In particular, the prototype implementation of our wireless application allows mobile consumers equipped with UMTS-enabled devices to exploit the Internet as a vast storehouse of music resources, where two different musical services are provided, namely:

A mobile song-on-demand distribution service
A mobile karaoke distribution service

The mobile song-on-demand distribution service permits to mobile users to download and to listen to MP3 files ^[6] on UMTS devices. Specifically, our wireless application exploits the background traffic class of UMTS to provide its users with (1) a simple and rapid Internet-based mobile access to a music-on-demand download service, (2) a robust and widely available music-on-demand distribution system based on the technique of replicated Web servers, and (3) the possibility of interactively customizing the use of the system.

From a user's perspective, it is worth noticing that different types of clients may exploit the developed service. In particular, our wireless application may be exploited by the following categories of users:

Music listeners may search for their favorite songs over the Internet, download them onto their UMTS devices, and play them at their convenience.
Music producers may wish to exploit our system to distribute their own music. (At the current state of the art, this type of user needs a regular wireline Internet connection in order to upload musical resources to the system.)
Musical service providers may exploit our system to organize, build, and maintain structured repositories of musical resources over the Internet for use by UMTS-enabled consumers.

Karaoke is an MTV-type multimedia entertainment service that has gained much popularity in Asia, the United States and Europe. With the advent of the wireless Internet and of Internet-enabled cellular phones, a growing demand is emerging for delivering such multimedia entertainment services to wireless handheld devices on a large scale. In this context, the mobile karaoke distribution service we have developed allows mobile users to download and to play multimedia karaoke clips constructed out of synchronized multimedia resources, such as music, text, and video. A karaoke clip is represented by means of a SMIL (Synchronized Multimedia Integration Language) file containing the formal specification of the media scheduling and synchronization activities concerning all the audio, video, and textual resources that compose a karaoke clip. ^[7]

The important experiences of P2P systems, such as Napster, ^[8] Freenet, ^[9] and Gnutella, ^[10] are at the basis of our music delivery services, but our Internet application is essentially new in the sense that it allows a reliable and distributed music sharing service over wireless UMTS links. As previously mentioned, the choice of adopting UMTS as the key technology for wireless access to the Internet has posed a set of technical challenges which will be discussed later in the chapter.

The reminder of this chapter is organized as follows. In Section 24.2, we discuss some technical obstacles we have surmounted for integrating wireless UMTS access technology with the Internet. In Section 24.3, alongside the operational description of our wireless Internet application we illustrate the design principles we have followed to design our system. Section 24.4 reports on a large set of performance results we have gathered from experimental trials conducted on the field. Section 24.6 provides an insight into some important research areas that have influenced our work. Finally, Section 24.7 concludes the chapter.

^[1]Bhagwat, P. and Sreenan, C.J., Eds., Future Wireless Applications, IEEE Wireless Commun., 9 (1), 6–59, 2002.

^[2]All about i-mode, http://www.nttdocomo.com/index.html, 2001.

^[3]WAP Architecture Specification, http://www1.wapforum.org/tech/terms.asp?doc=WAP-100-WAPArch-19980430-a.pdf.

^[4]Macedonia, M., Distributed file sharing: barbarians at the gates?, IEEE Comput., 33(8), 99–101, August 2000.

^[5]UMTS Forum, What is UMTS?, http://www.umts-forum.org/what_is_umts.html.

^[6]MP3 resources by MPEG.ORG, http://www.mpeg.org/MPEG/mp3.html.

^[7]W3 Recommendation, Synchronized Multimedia Integration Language (SMIL) 2.0 Specification, http://www.w3.org/TR/smil20/, 2001.

^[8]Napster official site, http://www.napster.com/

^[9]The Freenet Project, http://freenet.sourceforge.net.

^[10]Gnutella official site, http://gnutella.wego.com/.