[ 1 ] [5G vision and requirements]. Report. Beijing: IMT-2020 (5G) Promotion Group; 2014 May. Chinese.

[ 2 ] Liu G, Jin J, Wang Q, Dong J, Lou M, Huang Y, et al. Vision and requirements of 6G: digital twin and ubiquitous intelligence. Mob Commun 2020;44(6):3–9. Chinese. 链接1

[ 3 ] Liu G, Huang Y, Li N, Dong J, Jin J, Wang Q, et al. Vision, requirements and network architecture of 6G mobile network beyond 2030. China Commun 2020;17(9):92–104. 链接1

[ 4 ] [Vision and requirements for 2030+ (version 2.0)]. Report. Beijing: China Mobile Research Institute; 2020 Nov. Chinese.

[ 5 ] Nakamura T. 5G evolution and 6G. In: Proceedings of 2020 International Symposium on VLSI Design, Automation and Test; 2020 Aug 10–13; Hsinchu, China. Piscataway: IEEE; 2020. p. 1–5.

[ 6 ] [Technology trends for 2030+ white paper]. Report. Beijing: China Mobile Research Institute; 2020 Nov. Chinese.

[ 7 ] Saad W, Bennis M, Chen M. A vision of 6G wireless systems: applications, trends, technologies, and open research problems. IEEE Netw 2020;34(3):134–42. 链接1

[ 8 ] Li R, Toy M, Trossen D, Humphreys D, Sarian V, Bhandari S, et al. Network 2030: a blueprint of technology, applications and market drivers towards the year 2030 and beyond. Report. Focus Group Technologies on Network 2030; 2019 Jul.

[ 9 ] Weissberger A. ITU-R: future technology trends for the evolution of IMT towards 2030 and beyond (including 6G) [Internet]. IEEE ComSoc Technology Blog; 2020 Oct 16 [cited 2020 Nov 11]. Available from: https://techblog.comsoc.org/2020/10/16/itu-r-future-technology-trends-forthe-evolution-of-imt-towards-2030-and-beyond-including-6g/. 链接1

[10] [Network architecture outlook for 2030+ white paper]. Report. Beijing: China Mobile Research Institute; 2020 Nov. Chinese.

[11] Viswanathan H, Mogensen P. Communications in the 6G era. IEEE Access 2020;8:57063–74. 链接1

[12] Dong H, Zheng D, Wang R. The beyond 3G network structure and system applications. Mob Commun 2004;S2:26–8. Chinese. 链接1

[13] Li Z, Wang X, Huang Y, Liu G, Liu J, Tang H, editors. [Technology and standards of TD-LTE]. Beijing: Posts & Telecom Press; 2013. Chinese.

[14] Liu G, Fang M, Guan H, Li Y, Sun C. 5G mobile communication: a fully connected world. Telecommun Sci 2019;9:166. Chinese. 链接1

[15] TR 23.740: Study on enhancement of network slicing. 3GPP standard. France: 3GPP; 2018.

[16] Software-defined networking: the new norm for networks. Report. Open Networking Foundation; 2012 Apr.

[17] GSNFV-MAN 001-V1.1.1: Network functions virtualization (NFV); management and orchestration. ETSI standard. France: ETSI; 2014.

[18] New WID enhancement on management aspects of 5G service-level agreement [presentation]. In: 3GPP TSG-SA5 Meeting 87e; 2020 Feb 24–Mar 4; online; 2020.

[19] New WID on autonomous network levels [presentation]. In: 3GPP TSG-SA5 Meeting 88e; 2020 May 25–Jun 3; online; 2020.

[20] New WID self-organizing networks (SON) for 5G networks [presentation]. In: 3GPP TSG-SA5 Meeting 85; 2019 Sep 17–20; Newport Beach, CA, USA; 2019.

[21] Huawei. SP-180899: New WID on intent driven management service for mobile networks [presentation]. In: 3GPP TSG-SA5 Meeting 81; 2018 Sep 12– 14; Gold Coast, QLD, Australia; 2018.

[22] GS ZSM 002: Zero-touch network and service management (ZSM); reference architecture (V1.1.1). ETSI standard. France: ETSI; 2019.

[23] GS ZSM 001: Zero-touch network and service management (ZSM); requirements based on documented scenarios (V1.1.1). ETSI standard. France: ETSI; 2019.

[24] Our community [Internet]. Palo Alto: Telecom Infra Project; c2021 [cited 2020 Nov 11]. Available from: https://telecominfraproject.com/. 链接1

[25] Omar S. Rakuten Cloud platform is a blueprint for the future [Internet]. Cisco Blogs; 2019 Mar 22 [cited 2020 Nov 11]. Available from: https:// blogs.cisco.com/sp/rakuten-cloud-platform-is-a-blueprint-for-the-future. 链接1

[26] [Vision and requirements for 2030+ white paper]. Report. Beijing: China Mobile Research Institute; 2019 Nov. Chinese.

[27] Xie Y. The evolution of NB-IoT standard system and development of Internet of Things industry. Chin J Internet Things 2018;2(1):76–87. Chinese. 链接1

[28] Zhang L, Li F, Hu Z, Zhao Y, Cao G, Hu Y. Study on key technology and deployment scheme of LTE-eMTC. Des Tech Posts Telecommun 2018;7:1–5. Chinese. 链接1

[29] Mayer-Schönberger V, Cukier K, editors. Big data: a revolution that will transform how we live, work, and think. New York: Houghton Mifflin Harcourt; 2013.

[30] Zhou T, Pan Z, Cheng X. Developing tendency prediction of big data in 2019 from CCF TFBD. Big Data Res 2019;5(1):109–15. Chinese. 链接1

[31] Y.3173: Framework for evaluating intelligence levels of future networks including IMT-2020 (Study Group 13). ITU-T standard. Geneva: ITU; 2020.

[32] TR 37.816: Study on RAN-centric data collection and utilization for LTE and NR. 3GPP standard. France: 3GPP; 2019.

[33] TR 23.791: Study of enablers for network automation for 5G. 3GPP standard. France: 3GPP; 2019.

[34] Way forward on U-plane modifications to LTE baseline [presentation]. In: 3GPP TSG-RAN2 95bis; 2016 Oct 10–14; Kaohsiung, China; 2016.

[35] TS 38.321: 5G new radio-medium access control (MAC) protocol specification. 3GPP standard. France: 3GPP; 2021.

[36] TS 38.322: 5G new radio-radio link control (RLC) protocol specification. 3GPP standard. France: 3GPP; 2021.

[37] TS 38.323: 5G new radio-packet data convergence protocol (PDCP) specification. 3GPP standard. France: 3GPP; 2021.

[38] Wang W, Lu G, Chen X. Key technologies and challenges of commercial 5G core network. ZTE Tech J 2020;26(3):9–16. Chinese. 链接1

[39] Nie H, Zhao H, Mao C. Deployment issues and suggestions of 5G core network. ZTE Tech J 2020;26(3):3–8. Chinese.

[40] TR 38.801: Study on new radio access technology-radio access architecture and interfaces. 3GPP standard. France: 3GPP; 2017.

[41] Liu C, Lu L, Wang S, Hu Y. Prospects for a multi-access air–space-terrestrial integrated 6G network architecture. Mob Commun 2020;44(6):116–20. Chinese. 链接1

[42] Zhou L, Chen X. SVM hotspot identification for cellular networks. In: Proceedings of IEEE 5th International Conference on Computer and Communications; 2019 Dec 6–9; Chengdu, China. Piscataway: IEEE; 2019. p. 1103–7.

[43] Zhang C, Patras P. Long-term mobile traffic forecasting using deep spatiotemporal neural networks. 2017. arXiv:1712.08083.

[44] Dong R, She C, Hardjawana W, Li Y, Vucetic B. Deep learning for hybrid 5G services in mobile edge computing systems: learn from a digital twin. IEEE Trans Wirel Commun 2019;18(10):4692–707. 链接1

[45] Zhao Z, Zhang P, Huang H, Zhang X. User mobility modeling based on mobile traffic data collected in real cellular networks. In: Proceedings of 11th International Conference on Signal Processing and Communication Systems; 2017 Dec 13–15; Surfers Paradise, Australia. Piscataway: IEEE; 2017. p. 1–6. 链接1

[46] Y.DTN-ReqArch; Requirements and architecture of digital twin network. ITU-T standard. Geneva: ITU; 2021.