Yang-Soo Kwon

A non-interfering cognitive radio system for spectrum sharing

We present a cognitive radio beamformer for spectrum sharing with primary users. The proposed method generates orthogonal multiple beams for cognitive users using orthogonal subspaces and opportunistic beamforming methods to increase the sum-rate of cognitive radio systems. Simulations demonstrate that the proposed scheme does not cause interference for the primary users and provides a sum-rate capacity of 2.72bps/Hz for up to 20 cognitive users with two transmit antennas.

Combined opportunistic beamforming methodology

A combined opportunistic multiple beamforming method is presented that the first beam is designed with an aid of channel state information using uplink mid-amble and other beams are orthogonally generated to the first beam sequentially. The power allocation with SINR feedback increases overall throughput for the de- centralized systems. The advantages of the proposed scheme is that the first beam is not interfered by other beams guaranteeing quality of service (QoS) and other orthogonal beams are operated opportunistically to obtain multi user diversity. The computer simulation demonstrates that the proposed scheme is effective at a small number of users, which is common in cellular systems, and outperforms conventional spatial division multiple access (SDMA) opportunistic beamforming methods.

Multiband radio resource allocation for cognitive radio systems

A multi-band radio resource allocation method in cognitive radio systems is presented. To maximize the cell throughput with minimizing outage rate, multi-band intelligent radio resource management method is described. The cell division and spectrum sharing methodologies are also applied. The numerical simulations exhibit the maximum capacity with the lowest outage rate point is located in r=700m with p = q.