A Proposal of High-Flexibility Short-Range Cognitive Radio System

A new cognitive radio (CR) system for short-range high-capacity wireless communication is proposed. A transceiver selects 1 GHz-bandwidth main bands from the frequency range of 3-12 GHz, and places single-carrier modulated sub-bands at unused frequencies. The frequencies of main bands and sub-bands are flexibly changed according to the occupancy condition. A transceiver performs two kinds of carrier sensing. Longer duration carrier sensing is performed to recognize frequency occupancy conditions and determine the frequencies of main bands and sub-bands. Shorter duration carrier sensing is performed, which checks the sub-band frequencies just before transmitting to detect whether any primary system signal is included or not. The transceiver estimates the type of detected interference and transmission will be stopped if it is from a primary user. This system realizes the reduction of interference to other systems, and improves the throughput of the CR system itself. Furthermore, some of the key technologies to realize the proposed system are introduced.