A Probabilistic QoS-Aware User Association in Cell-Free Massive MIMO for Industry 4.0

Industry 4.0 requires wireless solutions to meet
the demanding reliability and latency requirements of cyber physical
systems serving many industrial sensors and actuators.
The cell-free massive multiple input multiple output (MIMO)
paradigm, exploiting both massive MIMO gains and cell-free
properties, is expected to play a crucial role in addressing
Industry 4.0 communication requirements. However, finding an
optimal user association to satisfy the quality of service (QoS)
requirements is critical. In this article, we propose a novel centralized
probabilistic user association algorithm to identify and
maximize the number of served users without relying on short term
channel state information to satisfy the QoS requirements.
In larger factories, approximately 90% of the total users are
satisfied. However, as the system becomes interference-limited
and is expected to meet challenging requirements, the number
of served users decreases. Nevertheless, the proposed solution
exhibits adaptability in maximizing the number of satisfied users.
Simulation results further prove the effectiveness of the proposed
solution in terms of achievable spectral efficiency and maximizing
the number of satisfied users across varying requirements and
factory sizes.