TABLE OF CONTENTS Technology is never adopted for technology's sake. For example, only hobbyists used personal computers (PCs) until a spreadsheet program, a "killer application", was developed. Then business needs and the benefits of small computers became apparent and drove PC technology into ubiquitous use. This led to the development of more applications, such as word processors, e-mail, and more recently the World Wide Web (WWW). Similar development is under way for wireless communication devices.
Reliable cellular telephony technology is now in widespread use, and new applications are driving the industry. Where these applications go next is of paramount importance for product developers. Cognitive radio (CR) is the name adopted to refer to technologies believed to enable some of the next major wireless applications. Processing resources and other critical enabling technologies for wireless killer applications are now available.
This chapter presents a CR roadmap, including a discussion of CR technologies and applications. Section 4.2 presents a taxonomy of radio maturity, and Sections 4.3 and 4.4 present more detailed discussions. Sections 4.5 and 4.6 are about enabling and required technologies for CRs. They present three classes of cognitive applications, one of which may be the next killer application for wireless devices. Conjectures regarding the development of CR are included in Section 4.7 with arguments for their validity. Highlights of this chapter are discussed in the summary in Section 4.8, which emphasizes that the technologies required for CR are presently available.
