tones alone are expected to be worth US$2.7 billion worldwide by 2010. Europe is expected to lead in revenue growth in the short term but to be overtaken by Asia-Pacific by 2007. From an application standpoint, there were 60 million ringback tone subscribers worldwide in 2005, and that number is forecast to grow to more than 300 million in 2009. Finally, the annual number of full-track down- loads is projected to reach 1 billion in 2008. The Handset Revolution Over the coming years, intelligence embedded into handsets will become increasingly dense, equipping handsets with features familier in the PC world and converting the traditional mobile phone into an advanced audiovisual device requiring fast, high-capacity wireless networks. In the future, the successful use of new mobile multimedia device services will demand more and more capacity from the network. (Chapters 14, "Wireless WANS," and 15, "WMANs, WLANs, and WPANs," discuss the developments under way to provide such networks.) The future will also bring what are called multiradio terminals that can deploy different network technologies, allowing the user to flexibly shift from one net- work to another while moving about between home, workplace, and hobbies. The user will automatically be connected to any number of network alternatives, such as GSM, GPRS, 3G, WLANs, WMANs, and WPANs, without interruptions. (Multi- radio technology is discussed in the following sections.) In the near term, we can expect an increasing number of devices embedded with utility and entertainment applications for both enterprise and consumer use. Road warriors and travellers will see a service portfolio that offers maps, time, cur- rency, and weather applications, all downloadable onto the handsets over the net- work. Whether it's games, ringtones, pictures, entertainment, sports, or lifestyle, there will be something for everyone. Software-Defined Radio One forthcoming application of multiradio technology is software-defined radio (SDR), a collection of hardware and software tech