Keynote speech 4: Cognitive radio and Australia's National Broadband Network

With the increasing demand for high data rate wireless communications services, the requirement for efficient spectrum utilization is on the rise. Generally speaking, the spectrum usage experiences vast temporal and geographic variations ranging from 15% to 85%. Thus, cognitive radio (CR) has received considerable attentions recently, and is becoming an essential part of the emerging wireless communications standard and systems, such as the IEEE 802.22 Wireless Regional Area Networks (WRAN).