Energy Efficient Multiple Association in CoMP Based 5G Cloud-RAN Systems

The architecture of cloud radio access networks (C-RANs) is envisioned as an attractive paradigm of 5G that takes advantages of both centralized baseband and coordinated multi-point(CoMP) processing in radio access networks. In C-RAN the data rate provisioning can be significantly improved due to the fractional frequency reuse performed by small cells. The dense deployment of small cells, however, incurs severe inter-tier and inter-cell interference turning the user association into a more challenging problem. Moreover, multi-cell association problem occurs in CoMP and control/user planes (C/U planes) splitting based C-RAN system where users are associated with more than one cells to support joint-transmission and reception method. In this paper, we consider multi-cell user association approach taking into account the data rate and aggregated interference of mobile users. We propose the posterior probability based user association and power allocation (P2UPA) method that depends on prior knowledge of the channel state information (CSI). The objective of the proposed method is to maximize the sum data rate of small cell users while maintaining the constraints of aggregated interference, power consumption, and data rate among small cell users. Finally, the sum data rate and energy efficiency performance of P2UPA are evaluated through simulations.