Chapter 17
Low-Power Spectrum Processors for Cognitive Radios
17.1 INTRODUCTION
Under the current license-based spectrum policy, it becomes more difficult to keep up user demand for better connectivity and higher data rate. Many spectrum segments, such as cell-phone band, are now crowded by big user groups, whereas other spectra are seldom used. Thus, advances in wireless technology have been urged to create a new wireless communication system to use spectrum more efficiently than in the past. Cognitive radio (CR) technology has been proposed as a promising solution for improving the efficiency of spectrum use by adopting a dynamic spectrum resource management concept [1-3]. The CR system is promising not only because it may improve the efficiency of spectrum use, but also because it promises improved connectivity and self-adaptability of channel environment.
There are distinctive movements in standardization groups to adopt the CR concept. Figure 17.1 is a road map of CR-based wireless applications for flexible use of spectrum for various applications. In November 2008, the U.S. Federal Communications Commission (FCC) approved the unlicensed use of white space, which enforces new ways of spectrum policy by letting secondary users use locally unused TV spectrum as broadband wireless communication services [3]. IEEE 802.22 wireless regional area network (WRAN) is being developed to provide broadband data communication service ...
