## 6 Conclusions  
This paper mainly studied the optimal radio resource allocation based on carrier aggregation technology for improving the energy efficiency in 5G system. The proposed energy-efficient sustainable resource optimization allocation scheme PEJA is verified through system simulation experiments. Compared with the NP-EJA, ERAA, EGA, and GA algorithms, PEJA achieves better energy-efficient performance in different user numbers and different maximum transmission powers and is also better than the comparison algorithm in throughput performance; PEJA algorithm has higher energy efficiency than PEJA-NC algorithm, which does not consider the CC handover of narrowband users. In conclusion, the proposed PEJA energy efficiency resource allocation scheme maximizes the system energy efficiency and achieves high throughput. J.L. : Conceptualization, Methodology, Software, Validation, Visualization, Writing--original draft. W.L. : Project administration, Conceptualization, Validation, Writing--review editing. All authors have read and agreed to the published version of the manuscript. This work has been in part supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China under grant (No.2019D01A30), University Scientific Research Program Youth Natural Science Foundation of Xinjiang Uygur Autonomous Region of China under grant ((No. XJEDU2018Y056), and NSFC under grant (No.61962058). Not applicable. Data Availability Statement: Data are contained within the article. The authors declare no conflict of interest. * [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Power allocation for energy efficiency maximization in downlink CoMP systems with NOMA. In Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), San Francisco, CA, USA, 19-22 March 2017; pp. 1-6. * [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON] Spectral-energy efficiency tradeoff in full-duplex two-way relay networks. _IEEE Syst. J._**2017**, _12_, 583-592. [CrossRef]
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