Minimizing executing and transmitting time of task scheduling and resource allocation in C-RANs

In each group of a Cloud Radio Access Network (C-RAN), a local controller controls a set of lightweight remote radio heads (RRHs) for connecting users nearby, and creates virtual machines (VMs) for executing user tasks. In this paper, the issue of jointly scheduling user tasks on VMs and allocating RRHs linked to users in C-RANs is advocated. We aim to approach the objective of minimizing the total time of task execution and content transmission of the joint issue. The problem for the objective is formulated as a 0/1 integer linear programming (ILP) under the constraint that a user and its task are scheduled to the RRH and the VM belonging to the same group. On the other hand, another 0/1 ILP is also formulated if the constraint of the RRH and the VM belonging to the same group is removed. Then, two algorithms by adopting rounding method are proposed to obtain the feasible solutions of the two 0/1 ILPs. Their approximation ratios are proved to be bounded competitively. The simulation results validate that the proposed algorithms outperform a very recently related work, and their solutions are very close to the optimal solutions of the two 0/1 ILPs. (C) 2020 Elsevier B.V. All rights reserved.