Energy-efficient RRH-association and resource allocation in D2D enabled multi-tier 5G C-RAN

The device-to-device (D2D) enabled cloud radio access network (C-RAN) is considered as a promising network model which provides high data rate and energy efficiency. In this paper, we formulate a joint mode selection, subchannel assignment (SA), power allocation (PA) and remote radio head (RRH)-association problem in D2D enabled single carrier frequency division multiple access based C-RAN in the uplink. This problem is mixed-integer non-linear problem which is extremely difficult to solve in its original form. To solve this problem, we propose an iterative technique which solves this problem in two stages; mode selection stage and joint SA, PA and RRH-association (SAPARA) stage. For mode selection, a link quality based technique is presented while, for joint SAPARA, we developed an iterative technique that solves this this problem in three steps such that SA and PA are carried out in the first and second step, respectively, while RRH-association is performed in the third step. Our results show the efficiency of the presented techniques.