Tomoya Horiguchi

A/D Converter Clipping Noise Suppression for High-Sensitivity Carrier-Sensing of Cognitive Radio Transceiver

A technique for suppressing the clipping noise of an analogue to digital converter (ADC) is proposed to achieve the high-sensitivity carrier-sensing of a cognitive radio transceiver. When a large bandwidth cognitive radio transceiver performs carrier-sensing, it must receive a radio wave that includes many primary user transmissions. The radio wave may have high peak to average power ratio and clipping noise may be generated. Clipping noise becomes an obstacle to the achievement of high- sensitivity carrier-sensing In the proposed technique, the original values of the samples clipped by an ADC are estimated by interpolation. Polynomial spline interpolation to the clipped signal is performed in the first step, and then SINC function interpolation is applied to the spline interpolated signal. The performance was evaluated and about 20 dB suppression of clipping noise was achieved with the medium degree of clipping.

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.

Proposal of an A/D Converter Clipping Noise Suppression Technique for High-Sensitivity Carrier-Sensing of Cognitive Radio Transceiver

A technique for suppressing the clipping noise of an analogue-to-digital converter (ADC) is proposed to realize a cognitive radio transceiver that offers high sensitivity carrier-sensing. When a large bandwidth cognitive radio transceiver performs carrier-sensing, it must receive a radio wave that includes many primary user transmissions. The radio wave may have high peak-to-average power ratio (PAPR) and clipping noise may be generated. Clipping noise becomes an obstacle to the achievement of high-sensitivity carrier-sensing. In the proposed technique, the original values of the samples clipped by an ADC are estimated by interpolation. Polynomial spline interpolation to the clipped signal is performed in the first step, and then SINC function interpolation is applied to the spline interpolated signal. The performance was evaluated using the signals with various PAPR. It has been found that suppression performance has a dependency on the number of samples clipped at once rather than on PAPR. Although there is an upper limit for the number of samples clipped at once that can be compensated with high accuracy, about 20dB suppression of clipping noise was achieved with the medium degree of clipping.