Structured Massive Access for Scalable Cell-Free Massive MIMO Systems

How to meet the demand for increasing number of users, higher data rates, and stringent quality-of-service (QoS) in beyond fifth-generation (B5G) networks? Cell-free massive multiple-input multiple-output (MIMO) is considered as a promising solution, which many wireless access points cooperate jointly serve users by exploiting coherent signal processing. However, there are still unsolved practical issues cell-free MIMO systems, whereof scalable implementation one most vital. In this paper, we propose new framework structured comprises initial algorithm, partial large-scale fading decoding (P-LSFD) strategy, two pilot assignment schemes, fractional power control policy. New closed-form spectral efficiency (SE) expressions with maximum ratio (MR) combining derived. The simulation results show that our proposed provides high SE when using local minimum mean-square error (LP-MMSE) MR combining. Specifically, algorithm schemes outperform their corresponding benchmarks, P-LSFD achieves scalability negligible performance loss compared conventional optimal (LSFD), controllable trade-off between user fairness average SE.