  The radio access network (RAN) part of the next-generation wireless networks
will require efficient solutions for satisfying low latency and high-throughput
services. The open RAN (O-RAN) is one of the candidates to achieve this goal,
in addition to increasing vendor diversity and promoting openness. In the O-RAN
architecture, network functions are executed in central units (CU), distributed
units (DU), and radio units (RU). These entities are virtualized on
general-purpose CPUs and form a processing pool. These processing pools can be
located in different geographical places and have limited capacity, affecting
the energy consumption and the performance of networks. Additionally, since
user demand is not deterministic, special attention should be paid to
allocating resource blocks to users by ensuring their expected quality of
service for latency-sensitive traffic flows. In this paper, we propose a joint
optimization solution to enhance energy efficiency and provide delay guarantees
to the users in the O-RAN architecture. We formulate this novel problem and
linearize it to provide a solution with a mixed-integer linear problem (MILP)
solver. We compare this with a baseline that addresses this optimization
problem using a disjoint approach. The results show that our approach
outperforms the baseline method in terms of energy efficiency.
