A Unified Framework for Distributed RIS-Aided Downlink Systems Between MIMO-NOMA and MIMO-SDMA

The combination of reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) has been recognized as a critical method to improve the sixth generation networks performance. In this paper, a distributed RIS-aided downlink multiple-input multiple-output (MIMO) NOMA systems with...

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Bibliographic Details
Published in:IEEE transactions on communications 2022-09, Vol.70 (9), p.6310-6324
Main Authors: Yang, Shizhao, Zhang, Jun, Xia, Wenchao, Ren, Yuan, Yin, Hao, Zhu, Hongbo
Format: Article
Language:English
Subjects:
Base stations
Clusters
Distribution functions
Downlink
Downlinking
ergodic rate
MIMO
MIMO communication
MISO communication
NOMA
Nonorthogonal multiple access
outage probability
Power system reliability
Probability
RIS
Signal to noise ratio
Statistical analysis
Wireless communication
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Summary:The combination of reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) has been recognized as a critical method to improve the sixth generation networks performance. In this paper, a distributed RIS-aided downlink multiple-input multiple-output (MIMO) NOMA systems with discrete phase shifts are studied, where the channel directions from base station to paired users can be manipulated with the assistance of RISs by employing the concept of signal alignment. In order to ensure base station can flexibly serve some users with NOMA and others users with spatial division multiple access, a unified precoder and decoder are provide to cancel inter-cluster interference. Subsequently, the channel statistics over Nakagami- m fading channels are derived for near and far users. In particular, considering the cascade channel gain may exists two different cases, Beaulieu series is further adopted to characterize their corresponding cumulative distribution function. In what follows, the outage probability and ergodic rate for three situations within one cluster are derived by utilizing the obtained channel statistics, respectively. Based on the derived results, we also analyze the diversity order and high signal-to-noise ratio slope to provide essential insights into the considered systems. Finally, simulation results are presented to reveal that: 1) selecting the setting of 3-bits resolution can realize a near-aligned performance for our proposed systems; 2) the cascade channel statistic caused by RIS can be evaluated with any number of RIS element and any channel gain via Beaulieu series.
ISSN:0090-6778
1558-0857
DOI:10.1109/TCOMM.2022.3188020