Low-Complexity RF Chains Activation Based on Hungarian Algorithm for Uplink Cell-Free Millimetre-Wave Massive MIMO Systems

The increasing demand for throughput, ultra-low latency, ultra-high reliability, and ubiquitous coverage have made researchers explore several novel solutions to set the basis for future generations of wireless communications. These demands, however, will consume a significant amount of resources, particularly in the case of cell-free millimetre-wave (mm-Wave) massive multiple input multiple output systems (MIMO), which is the promising approach for future wireless generations. In this paper, we propose a novel and low-complexity matching approach to dynamically activate a set of radio frequency (RF) chains based on the Hungarian algorithm to maximize the total energy efficiency in the uplink of the cell-free mm-Wave massive MIMO systems. Simulation results demonstrate that our proposed scheme achieves up to 13.5%, 20% and 58.7% energy efficiency improvement compared to state-of-the-art adaptive RF chains activation (ARFA), random access point activation and fixed activation scheme when all RF chains at each AP are switched on, respectively. In addition, compared to the ARFA scheme, the proposed matching scheme achieves a complexity reduction ratio of up to 189.6%.