Open AccessA combinatorial precoding scheme of cell‐free massive MIMO with channel aging
Author(s) -
Fang Hao,
Hu Han,
Yang Longxiang,
Zhang Yao,
Qiao Xu
Publication year - 2022
Publication title -
iet communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.355
H-Index - 62
eISSN - 1751-8636
pISSN - 1751-8628
DOI - 10.1049/cmu2.12444
Subject(s) - precoding , telecommunications link , zero forcing precoding , computer science , beamforming , spectral efficiency , mimo , channel (broadcasting) , interference (communication) , control theory (sociology) , algorithm , electronic engineering , mathematics , telecommunications , engineering , artificial intelligence , control (management)
Here, we investigate the precoding schemes for the downlink data transmission of a time‐division duplex cell‐free massive multiple‐input multiple‐output (MIMO) system with channel aging, which arises from the user mobility. Closed‐form spectral efficiency (SE) expressions of the downlink with the normalized conjugate beamforming (NCB), and the full‐pilot zero‐forcing (FZF), are derived, which are used for the analytical system performance evaluation. Then, a novel combinatorial precoding scheme with enhanced system SE performance, which adopts either NCB or FZF according to each user channel aging condition, is proposed. Moreover, a pilot allocation strategy is proposed to alleviate the extra interference brought by the combinatorial precoding scheme. Also, a statistical channel cooperative power control is employed to further improve the performance for all the above precoding schemes. Numerical results show that the proposed precoding scheme can substantially improve the average downlink SE.