## 5 Conclusions  
This paper proposes a design for a switchable coupled relay model to assist a massive MIMO-NOMA wireless network in serving multiple devices and extending a network's lifespan. A diagram of two transmission blocks illustrates signal propagation and EH processing. Propagation and formulations are analyzed. We derive the closed-form novel expressions for OP at the coupled relays and devices. The theoretical results show that the massive MIMO technique in combination with TAS and SWIPT protocols in an underlay  
Figure 6: System throughput in even transmission blocks.  
Figure 7: EE of a MIMO network (odd transmission block) compared to a massive MIMO network (even transmission block).  
cooperative NOMA network provides higher throughput and consumes lower energy. The obtained results verify the massive MIMO technique as effective for 5G wireless networks. The present paper offers the potential for the practical application of a massive MIMO-NOMA network model assisted by switchable coupled relays, for example in a water environment where relays and devices are barely powered. Our massive MIMO-NOMA assisted by switchable coupled relays in combination with TAS and EH protocols can not only improve OP and system throughput performance but also extend the network's lifespan. Specifically, EH at the relay may be used to forward signals without consuming the relay's own energy. This is promising as a potential solution in extending a network's lifespan.  
These authors contributed equally to this work. All authors have read and agreed to the published version of the manuscript.  
This research was funded by The Ministry of Education, Youth and Sports within the grant reg. No. SP2021/25 and partially within the Large Infrastructures for Research, Experimental Development, and Innovations project reg. No. LM2018140.  
Not applicable.  
Data Availability StatementData was randomly generated when we were running program. There is no data to share.  
We are especially grateful for our reviewers' comments and all the constructive suggestions that have helped us improve the quality and presentation of our manuscript.  
The authors declare no conflict of interest. The funders had no role in the study's design, the collection, analysis and interpretation of data, writing of the manuscript, nor in the decision to publish the results.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l}
5G & Fifth-Generation \\ AF & Amplify-and-Forward \\ AWGN & Adaptive White Gaussian Noise \\ BS & Base Station \\ CSI & Channel State Information \\ DF & Decode-and-Forward \\ EE & Energy Efficiency \\ EH & Energy Harvesting \\ FD & Full-Duplex \\ HD & Half-Duplex \\ IoTS & Internet of Things \\ MIMO & Multi-Input-Multi-Output \\ NOMA & Non-Orthogonal Multiple Access \\ OP & Outage Probability \\ PA & Power Allocation \\ PS & Power Splitting \\ QoS & Quality of Service \\ RF & Radio Frequency \\ SIC & Successive Interference Cancellation \\ SINR & Signal-to-Interference-plus-Noise Ratio \\ SISO & Single-Input-Single-Output \\ SNR & Signal-to-Noise Ratio \\ SWIPT & Simultaneously Wireless Information Power Transmit \\ TAS & Transmit Antennas Selection \\ TS & Time Switching \\ WIP & Wireless Information Power \\ \end{tabular}