Bottleneck Effects Elimination for Cooperative Cognitive Radio Networks: A New Dimension of Time Slot Rearrangement

In this paper, a new dimension of time slot rearrangement is added into the cooperative cognitive radio (CR) networks. The key idea is to rearrange the time durations of Phase-I and Phase-II for the two-hop relay networks such that the throughput of the two phases can be balanced. In this fashion, the so-called bottleneck effect in the two-hop relay networks can be completely eliminated and, most importantly, the end-to-end throughput can be largely improved. For the purpose of better utilization of spectrum holes, the projected-channel singular-value-decomposition (P-SVD) and direct-channel SVD (D-SVD) techniques are applied to use the spatial spectrum holes and temporal spectrum holes, respectively. The simulation and analytical results prove that the proposed bottleneck effect elimination scheme can significantly improve the end-to-end throughput. The impacts of the continuous and period sensing as well as the effects of secondary users´ frame duration are also investigated to make the discussions complete. Some suggestions for future works are also provided.