Sunghwan Sohn

Weighted-Collaborative Spectrum Sensing in Cognitive Radio

Cognitive radio is an advanced enabling technology for efficient utilization of under-utilized spectrum since it is able to sense the spectrum and use the frequency when the primary users are absent. Recent investigation suggests that spectrum sensing is compromised when a user experiences fading or shadowing. In order to combat such effects, collaborative sensing is presented. However, the conventional collaborative sensing is not effective when users suffer from different fading environments. In this paper, we propose a weighted-collaborative scheme to improve the spectrum sensing performance under fading environment. The analysis of the simulation results proves that the weighted-collaborative scheme improves sensing performance obviously.

Weighted-Cooperative Spectrum Sensing Scheme using Clustering in Cognitive Radio Systems

Cognitive radio is an advanced technology for efficient utilization of under-utilized spectrum since it is able to sense the available spectrum and use empty frequency bands if there is no use of primary user. These sensing observations are forwarded a cognitive radio base-station through fading channels, the sensing performance will be severely degraded. In order to mitigate this effect, weighted-cooperative sensing was considered to be a promising way in our previous work, which combines the sensing result of each CR user to improve the performance. However, in practical, the probability of detection is unavailable to calculate in each user. In this paper, we propose a weighted-cooperative sensing scheme using clustering to improve the performance and to overcome the critical problem. Numerical results show that the sensing performance is improved obviously as opposed to conventional spectrum scheme.

An Interference Mitigated and Power Efficient Adaptive Beamforming Algorithm in Cognitive Radio

By applying smart beamforming technologies, it is effective to protect primary user (PU) while guarantee that cognitive user (CU) has better spectrum sharing with PU in a rarely conflictual manner. In this paper, firstly, we implement direction of arrival (DOA) estimation for obtaining the location information of signals, then exploit uniform circular array antenna applying adaptive algorithm to achieve desired transmit beamforming gains in the required directions. The simulation results demonstrate that the proposed beamforming algorithm achieves desired beamforming pattern and higher power efficiency.