Sociality Regime in User-Centric Clustering for Energy-Efficient Cell-free MIMO Networks

The optimal cluster of access points (APs) for user equipment (UEs) is a crucial task to maximize the energy efficiency of cell-free networks. It is a complex problem, which becomes even difficult to solve when we aim to satisfy all UEs with respect to their requested quality of service (QoS). In this context, finding a balanced solution is challenging, in particular, due to the conflicting interests between APs and UEs. This paper considers the sociality regime of UEs, being either selfish, egalitarian or altruistic, which expresses their willingness to contribute to such a balance. To solve this problem, we first cast it into a many-tomany social matching game, during which, a UE may accept or reject a matching operation depending on its sociality regime. Hence, we propose two novel algorithms based on deferred acceptance (DA) and early acceptance (EA) matching games. In the DA game, APs buffer UE association requests based on their preferences and conduct the final association decision at the end of game. In contrast, in the EA game, the decision to associate a UE with an AP is immediate upon receipt of the request, which reduces decision-making times at the cost of a sub-optimal matching strategy. Numerical results show the significant impact of UEs sociality regime on their QoS satisfaction and network energy efficiency for both algorithms, with the egalitarian regime proving the best performance trade-off.