SDR implementation of cognitive radio: Sensing and disjoint spectrum access

This paper presents the activities in realizing and testing cognitive radio system by means of a software defined radio. The first part of this prototype is the sensing part which scans the TV band (100-700 MHz) to find the vacant spectrum hole. The signal´s cyclostationary feature and the chi-square test are used to judge the signal existence. The demo can detect CMMB and DMB-T signal by cyclostationary detector and detect PAL and other unknown format signal by energy detector. The other part of this prototype is discontinuous spectrum transmission implementation in spectrum hole which has two independent OFDM links on two separated carriers. The valid data sub-carriers in each OFDM link can be configured in a flexible way.