# Wireless Multi-Node uRLLc B5G/6G Networks for Critical Services in Electrical Power Systems
## 5 Conclusions  
For the critical services in power systems, such as distributed generation, charging piles, load control service, fault diagnostics and removal, and so forth, the data transmission requires very stringent reliability and latency, but the original OFDM transmission scheme is vulnerable to external and internal jamming/interference and cannot meet the transmission targets. In this paper, inspired by the PHY and MAC techniques in the 5G standards, a novel OFDM/FHMA system based on the mini-slot frame structure was proposed for the use cases of electric power services. The FHMA was imposed in subcarriers of OFDM to enhance the reliability. Furthermore, the retransmission mechanism based on the mini-slot structure was integrated into the OFDM/FHMA signals so as to reduce the latency. The numerical tradeoff between reliability and latency in the proposed system was derived. The analysis and simulation revealed that the OFDM/FHMA system based on the mini-slot structure can offer stable transmission reliability up to 99.999% and ms-level latency, even in the harsh wireless environment. Thus, our proposed system could become one of the techniques with the most potential in future B5G/6G uRLLc networks for power system applications.  
Note that this paper only concentrated on the designs and analysis of the wireless OFDM/FHMA uRRLc network for reliable and latency-critical services in power systems, without the consideration of the impact of communication on the services' metrics, i.e., fault operation probability. Thus, in future work, the theoretical relation between the transmission performance of the proposed uRLLc network and the specific power system metrics will be investigated.  
Conceptualization, Y.Z. and Q.Z.; methodology, H.X. and S.D.; software, Q.Z.; validation, S.D. and M.M.; formal analysis, Q.Z. and H.X.; investigation, Q.Z.; resources, W.W. and Q.Z.; data curation, W.W.; writing--original draft preparation, Y.Z., H.X. and Q.Z.; writing--review and editing, Y.Z. and H.X.; visualization, W.W.; supervision, Y.Z., S.D. and Q.Z.; project administration, H.X.; funding acquisition, H.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by \"Research on the interconnection and interactive technology of the source-network-load-storage under the new power system of Sichuan\", which is sponsored by the State Grid Sichuan Electric Power Company.  
Not applicable.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**SNR (dB)** & **No. of Frequency Slots** & \begin{tabular}{c} **99.9\%** \\ \end{tabular} & \
\begin{tabular}{c} **99.99\%** \\ \end{tabular} &
\begin{tabular}{c} **99.999\%** \\ \end{tabular} \\ \hline \multicolumn{5}{c}{**Times of Retrans. (\(N\))**} \\ \cline{2-5}
**0** & \(N_{h}=20\) & 4 & 6 & 7 \\ \cline{2-5}
**8** & \(N_{h}=80\) & 4 & 6 & 7 \\ \hline \multirow{2}{*}{**16**} & \(N_{h}=20\) & 2 & 3 & 4 \\ \cline{2-5}  & \(N_{h}=80\) & 2 & 3 & 3 \\ \hline \multirow{2}{*}{**24**} & \(N_{h}=20\) & 2 & 2 & 3 \\ \cline{2-5}  & \(N_{h}=80\) & 2 & 2 & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The tradeoff between reliability and latency under different system parameters.