Energy Efficient and Delay-Guaranteed User Association Algorithm for O-Ran

Open radio access network (O-RAN) is one of the key solutions envisaged to meet the ever increasing and stringent quality of service (QoS) demands of emerging applications and services supported by beyond 5G networks. In addition to meeting these QoS demands, O-RAN also promotes vendor diversity and interoperability by disaggregating the radio access network (RAN) into different units, namely the central unit (CU), distributed unit (DU), and radio unit (RU). However, the disaggregation introduces a new challenge of ensuring seamless interoperability between the various units with a view to ensuring that the QoS of the user equipments (UEs) is met and the energy consumption of the system is managed efficiently. In this paper, we focus on jointly optimizing UE association and RU energy consumption. We express the problem as an optimization problem and propose a scheme that determines the optimal RU among potential RUs that a UE should be associated to while minimizing the total used RUs. Moreover, we employ a power control mechanism that enables idle RUs without associated UEs to be put in sleep mode. To show the efficiency of the proposed algorithm, we evaluated it against some state of the art (SoA) solutions. The results indicate that the proposed solution minimizes energy consumption by about 171 % and 32 % under low and high number of UEs, respectively, while incurring a paltry 3.2% increase in access network delay for UEs without violating their delay requirements.