Spectral Efficient Cognitive Radio Transmission using Full Duplex Communication

Background/Objectives: The rapid growth of demand for ever-increasing data rate and wireless services results in spectrum scarcity. Cognitive radio technology is used as solution for this problem. Methods/Statistical Analysis: Spectrum sensing is the key mechanism used to share the spectrum in cognitive radio which will solve the spectrum scarcity problem. Conventional cognitive radio is operated in half-duplex mode which fist sense the spectrum hole and transmit if spectrum hole is found. This listen and talk approach has the constraint of losing transmission opportunities during sensing or has the Risk of undetectable collisions during transmission. This problem can be rectified by operating the cognitive radio in full duplex mode. Findings: Modern full-duplex wireless radio transceivers will be capable of simultaneous spectrum sensing and transmission. But one of the main issues in the full duplex simultaneous sensing and transmission is the residual self-interference.In this paper a full duplex cognitive radio with two antennas (2x2 MIMO) which will provide for higher physical isolation is proposed with the self-interference cancelling technique. The technique consists of a power control and interference cancellation filter or self-interference whitening filter. Since the full-duplex system, radios transmit and sense simultaneously in the same frequency band at the same time, providing improvement in spectral efficiency over a half-duplex system. Applications/Improvements: The result shows that the proposed full duplex cognitive radio provides spectral efficiency of 5.2 bits/Hz/sec at 11dB SNR but the conventional half duplex cognitive radio provides only 2 bits/Hz/sec.