Coverage Analysis for K-Tier Heterogeneous Networks with Multi-Cell Cooperation

Multi-cell cooperation is a promising technique used to mitigate the dominant interferences in heterogeneous networks (HetNets). Considering the rapid fluctuation of actual channel, we propose a multi-cell cooperation scheme named randomly selected cooperation with threshold (RSC-T), where the nearest BS in each tier is selected to transmit the user´s data only when its instantaneous signal power received at a typical user is greater than a predetermined connecting threshold. Based on the proposed scheme, we derive integral expression for downlink coverage probability, and characterize it for a special case of two-tier HetNets. Comparison between RSC-T and traditional maximum- received-power (MRP) association scheme which always selects a BS with the strongest received signal power at the typical user is showed through numerical results and simulations. The numerical results indicate that (1) to get better performance than MRP, the connecting threshold should be below a critical point and the critical point increases with coverage SINR threshold. (2) there is always an optimal BSs density that provide the best coverage and the optimal density increases with connecting threshold.