Multi-user reception in 5G Cloud-RAN: a practical design

Cloud Radio Access Network (C-RAN) is becoming more then ever timely in 5G for dense network deployments, but its design has to be adapted to 5G requirements. To ensure high uplink throughput in cell edge regions affected by inter-cell interference, C-RAN enables to apply Non-Orthogonal Multiple Access (NOMA) techniques among cells. In this paper, we propose a high performance and efficient end-to-end uplink transmission scheme dealing with practical constraints of both communication interfaces of C-RAN architecture, i.e., the wireless one between the users and the Remote Radio Heads (RRHs), and the fronthaul links between the RRHs and the central processing unit. Adapting multi-cell NOMA receiver to practical constraints such as receiver complexity and delay allows to improve spectral efficiency and cell-edge throughput. Optimizing the fronthaul rate allocation to maximize the benefit of the transmissions allows to efficiently use the fronthaul links following the estimated channel gains and the cost of fronthaul communications. We propose a model that includes the overall throughput of NOMA transmissions in C-RAN and the price to pay for the fronthaul usage in various deployment scenarios. Considering practical constraints of C-RAN, our strategy enables to realize uplink multi-cell multi-user processing, one of the main C-RAN features, in a cost-efficient manner.