Multi-Band Ad-Hoc Cognitive Radio for Reducing Inter System Interference

The cognitive radio is a secondary wireless communication system that can overlap the frequency band assigned to the primary system by recognizing the frequency status. Ad-hoc cognitive radio is considered for realizing the cognitive radio by using multi-hop communication networks without giving the large interference toward the primary system. We have proposed the STBC distributed ARQ system applied to the ad-hoc cognitive radio for realizing effective cognitive radio. This system can realize a multi-hop communication from the source terminal to the destination terminal without deciding the reliable route in advance. However, the affect of inter-system interference has not been evaluated yet. In this paper, in order to keep the interference level low at the receiver of the primary system, the permissible maximum transmit power of the cognitive terminals is analytically derived. Moreover, we propose a novel STBC distributed ARQ using multifrequency band for improving the performance of the ad-hoc cognitive radio due to the small transmit power and the large interference from the primary system. Finally, we confirm the effectiveness of the proposed system by using computer simulations