Flexible Function Splitting and Resource Allocation in C-RAN for Delay Critical Applications

The concept of cloud radio access network (C-RAN) architecture is being proposed to fully meet the requirements of 5G mobile networks. Thanks to the centralized cloud baseband unit (BBU), C-RAN reduces the energy consumption and cost of deployment significantly. However, it suffers from stringent fronthaul capacity and latency which are substantial in delay critical applications. Splitting up the processing functionalities between the control unit (CU) and distributed units (DUs) can mitigate fronthaul load and relax their requirements with the expense of an increase in power consumption. In this paper, we investigate joint access and fronthaul resource allocation problem for delay critical applications where the objective is minimizing the sum of normalized total power and fronthaul bandwidth consumption. We consider a downlink scenario and incorporate the total end-to-end delay components. For simplicity, linear models are assumed between function splitting (FS) levels and decreased fronhaul load as well as increased processing power. Different delay requirements affect our objective function and enforce a different FS level. We establish a flexible decision about the best FS level, which minimize our objective. Simulation results demonstrate that the delay constraint has a significant impact on the required fronthaul bandwidth and power consumption, which are directly related to the cost of the network. Moreover, flexible selecting function split level can achieve up to 40% gain in reducing the total utility (i.e., the sum of normalized total power and fronthaul required bandwidth).