通過 C-V2X 的發展，本文提出了一種稱為“提早式小型基地台車載網路資料卸載 (E-SCDO)”方法，該方法使用 C-V2V 和 C-V2I 通信技術來實現從大型基地台(macro cell)到小型基地台(small cell)無線行動網路資料流量的卸載。令V^m為當前與大型基地相連且不在任何小型基地台訊號覆蓋範圍內的車輛； 令V^s為在小型基地台訊號覆蓋範圍內並與其連接的車輛。如果 V^m 和 V^s 可以使用 C-V2V sidelink 直接相互通信，那麼 V^m 可以通過 V^m↔V^s↔small cell 的V2V2I E-SCDO路徑進行 E-SCDO，直到V^m進入小型基地台的訊號覆蓋範圍內進行由V^m自己直接小型基地台的資料卸載。由於（1）有許多車輛在小型基地台的訊號覆蓋範圍內，並且(2)有很多車輛在小型基地台的訊號覆蓋範圍之外，但可以與一輛或多輛在小型基地台的訊號覆蓋範圍內的車輛連接，因而此篇論文提出了基於多接入邊緣計算 (MEC) 的 E-SCDO 方法，稱為 SideLink Assisted (SLA) E-SCDO，以配對合適的車輛具有 E-SCDO。使用此論文提出的 SLA E-SCDO 方法，讓每輛車定期向 MEC 服務器報告其資訊； 然後 MEC 服務器使用拍賣算法(Auction algorithm)並根據提出的效用函數計算每個可能的 V2V2I E-SCDO 路徑的效用，並選出最可行的一些 V2V2I E-SCDO 路徑。為了保持 V^m X 的 SLA E-SCDO運作，一旦 V^m X 和 V^s Y 之間的鏈接意外斷開，MEC 服務器將為 V^m X找一個的替代 V^s Z ，來保持 V^m X 的 SLA E-SCDO運作。由性能評估結果來看，此論文所提出的SLA E-SCDO方法優於傳統的自行直接式小型基地台資料卸載方法，並提高了無線行動網路資料分流的性能。

Through the development of C-V2X, a small cell data offloading approach called “Early Small Cell Data Offloading (E-SCDO)” that uses C-V2V and C-V2I communication technologies was proposed in this work to achieve offloading network data traffic from the macro cell to the small cell for vehicles. Let V^m be a vehicle that currently connects with the macro cell and is not inside the signal coverage of any small cell; let V^s be a vehicle that is inside the signal coverage of the small cell and connect with the small cell. If V^m and V^s can communicate with each other directly using a C-V2V sidelink, then V^m can have the E-SCDO through the path of V^m↔V^s↔small cell, which is called a V2V2I E-SCDO path, until V^m enters into the signal coverage of the small cell to have the self-small cell data offloading. Since (1) there are many vehicles that are inside the signal coverage of the small cell and (2) there are many vehicles that are outside the signal coverage of the small cell but can connect with one or more vehicles inside the signal coverage of the small cell, this work proposed the Mobile Edge Computing (MEC)-based E-SCDO method called SideLink Assisted (SLA) E-SCDO to select suitable vehicles to have E-SCDO. Using the proposed SLA E-SCDO method, each vehicle periodically reports its context to the MEC server; then the MEC server uses the Auction algorithm to derive feasible V2V2I E-SCDO paths based on the proposed utility function, which calculates the utility of each possible V2V2I E-SCDO path based on vehicles’ reported contexts. To keep the SLA E-SCDO for a V^m X, once the link between V^m X and V^s Y is unexpectedly broken, the MEC server will find the alternative V^s Z for V^m X to keep V^m X’s SLA E-SCDO as long as possible. The performance evaluation results shown that the proposed SLA E-SCDO method is better than the traditional self-small cell data offloading method and enhance the performance of network data offloading.

[1] M. De Ree, G. Mantas, A. Radwan, S. Mumtaz, J. Rodriguez and I. E. Otung, "Key Management for Beyond 5G Mobile Small Cells: A Survey," IEEE Access, VOL. 7, pp. 59200-59236, 2019
[2] M. H. C. Garcia, A. Molina-Galan, M. Boban, J. Gozalvez, B. Coll-Perales, T. Şahin and A. Kousaridas, "A Tutorial on 5G NR V2X Communications," IEEE Communications Surveys & Tutorials, pp. 1-1, 2021.
[3] A. Singh and B. Singh, "A Study of the IEEE802.11p (WAVE) and LTE-V2V Technologies for Vehicular Communication," in Proceedings of the 2020 International Conference on Computation, Automation and Knowledge Management (ICCAKM), Dubai, United Arab Emirates, pp. 157-160, 2020.
[4] A. K. Ligo, J. M. Peha, P. Ferreira and J. Barros, "Throughput and Economics of DSRC-Based Internet of Vehicles," IEEE Access, VOL. 6, pp. 7276-7290, 2018.
[5] K. Kiela, V. Barzdenas, M. Jurgo, V. Macaitis, J. Rafanavicius, A. Vasjanov, L. Kladovscikov, and R. Navickas, ‘‘Review of V2X–IoT standards and frameworks for ITS applications,’’ Appl. Sci., VOL. 10, no. 12, p. 4314, Jun. 2020.
[6] S. Lien, D. Deng, C. Lin, H. Tsai, T. Chen, C. Guo and S. Cheng, "3GPP NR Sidelink Transmissions Toward 5G V2X," IEEE Access, VOL. 8, pp. 35368-35382, 2020.
[7] 3GPP, "TR 21.914 Release 14 Description; Summary of Rel-14 Work Items (v14.0.0, Release 14)," 3GPP, Tech. Rep., May 2018.
[8] 3GPP, “TR 36.843 Release 13 Study on LTE Device to Device Proximity Services: Radio Aspects (V12.0.0),” 3GPP, Tech. Rep., Mar. 2014.
[9] S. Ha, W. Yoo, H. Kim and J. -M. Chung, "C-V2X Adaptive Short-Term Sensing Scheme for Enhanced DENM and CAM Communication," IEEE Wireless Communications Letters, VOL. 11, no. 3, pp. 593-597, March 2022, doi: 10.1109/LWC.2021.3137471.
[10] T. Kim, G. Noh, J. Kim, H. Chung and I. Kim, "Enhanced Resource Allocation Method for 5G V2X Communications," Proceedings of 2021 International Conference on Information and Communication Technology Convergence (ICTC), 2021, pp. 621-623, doi: 10.1109/ICTC52510.2021.9620952.
[11] K. Sehla, T. M. T. Nguyen, G. Pujolle and P. B. Velloso, "Resource Allocation Modes in C-V2X: From LTE-V2X to 5G-V2X," IEEE Internet of Things Journal, VOL. 9, NO. 11, pp. 8291-8314, 1 June1, 2022, doi: 10.1109/JIOT.2022.3159591.
[12] ETSI ITS. “Intelligent transport system (ITS); vehicular communications; basic set of applications; analysis of the collective-perception service (CPS),” ETSI TR 103 562 V2.1.1, Dec. 2019.
[13] H.-J. Günther et al., “The effect of decentralized congestion control on collective perception in dense traffic scenarios,” Comput. Commun., VOL. 122, pp. 76–83, Jun. 2018.
[14] ETSI ITS. “LTE; Service requirements for V2X services, 3GPP TS 22.185 version 16.0.0 Release 16, 2020.
[15] P. Mogensen et al., "LTE Capacity Compared to the Shannon Bound," 2007 IEEE 65th Vehicular Technology Conference - VTC2007-Spring, 2007, pp. 1234-1238, doi: 10.1109/VETECS.2007.260.
[16] K. M. Addali, S. Y. B. Melhem, Y. Khamayseh, Z. Zhang, and M. Kadoch, "Dynamic Mobility Load Balancing for 5G Small-Cell Networks Based on Utility Functions," IEEE Access, VOL. 7, pp. 126998- 127011, 2019.
[17] Y. M. Abdelradi, A. A. El-Sherif and L. H. Afify, "A Queueing Theory Approach to Small-Cell Assisted IoT Traffic Offloading," 2019 IEEE Global Conference on Internet of Things (GCIoT), 2019, pp. 1-7, doi: 10.1109/GCIoT47977.2019.9058402.
[18] M. Pan, T. Lin, C. Chiu and C. Wang, "Downlink Traffic Scheduling for LTE-A Small Cell Networks With Dual Connectivity Enhancement," in IEEE Communications Letters, VOL. 20, no. 4, pp. 796-799, April 2016, doi: 10.1109/LCOMM.2016.2522404.
[19] T. Sheu and J. Sie, "A Dynamic Adjustment Scheme in Handover Thresholds for Off-loading LTE Small Cells, "Proceedings of 2018 IEEE International Conference on Applied System Invention (ICASI), pp. 180-183, 2018, doi:10.1109/ICASI.2018.8394562.
[20] Y. Saleem, N. Mitton and V. Loscri, "A Vehicle-to-Infrastructure Data Offloading Scheme for Vehicular Networks with QoS Provisioning," 2021 International Wireless Communications and Mobile Computing (IWCMC), 2021, pp. 1442-1447, doi: 10.1109/IWCMC51323.2021.9498708.
[21] J. Feng and Z. Feng, "A Vehicle-assisted Offloading Scheme for Hotspot Base Stations on Metropolitan Streets," in Proceedings of the 28th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC2017), Montreal, QC, Canada, pp. 1-6, 2017.
[22] C.-M. Huang, M.-S. Chiang, D.-T. Dao, H.-M. Pai, S. Xu, and H. Zhou, “Vehicle-to-Infrastructure (V2I) offloading from cellular network to 802.11p Wi-Fi network based on the software-defined network (SDN) architecture,” Veh. Commun., VOL. 9, pp. 288–300, Jul. 2017.
[23] C.-M. Huang, S.-Y. Lin, and Z.-Y. Wu, "The k-hop-limited V2V2I VANET Data Offloading using the Mobile Edge Computing (MEC) Mechanism," Vehicular Communications, VOL. 26, 2020.
[24] C. M. Huang and C. F. Lai, “The Delay-Constrained and Network-Situation-aware V2V2I VANET Data Offloading based on the Multi-access Edge Computing (MEC) Architecture” IEEE Open Journal of Vehicular Technology, VOL. 1, pp. 331-347, October 2020.
[25] K. Xiong, Y. Zhang, P. Fan, H. Yang and X. Zhou, "Mobile Service Amount Based Link Scheduling for HighMobility Cooperative Vehicular Networks," IEEE Transactions on Vehicular Technology, VOL. 66, NO. 10, pp. 9521-9533, Oct. 2017.
[26] Q. Zheng, K. Zheng, P. Chatzimisios, H. Long, and F. Liu, “A Novel Link Allocation Method for Vehicle-to-Vehicle-based Relaying Networks,” Transactions on Emerging Telecommunications Technologies, VOL. 27, NO. 1, pp. 64-73, Jan. 2016.
[27] D. De Couto, D. Aguayo, J. Bicket, and R. Morris, “A High-throughput Path Metric for Multi-hop Wireless Routing,” Proceedings of the ACM Annual International Conference on Mobile Computing and Networking (MOBICOM), pp. 134-146, San Diego, CA, Sep. 2003.
[28] M. Khosla, A. Anand, “Revisiting the auction algorithm for weighted bipartite perfect matchings,” arXiv preprint arXiv:2101.07155, Jan. 2021.
[29] ETSI ITS. “Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of Applications; Part 2: Specification of Cooperative Awareness Basic Service,” ETSI EN 302 637-2, Apr. 2019.
[30] M. Drago, T. Zugno, M. Polese, M. Giordani, M. Zorzi, "Millicar - An ns-3 Module for MmWave NR V2X Networks," Proc. of the Workshop on ns-3 (WNS3), 2020.
[31] M. Behrisch, L. Bieker, J. Erdmann, and D. Krajzewicz, “SUMOsimulation of urban MObility-an overview,” in Proc. 3rd Int. Conf. Adv. Syst. SIMUL, 2011, pp. 63–68.
[32] D.P. Bertsekas. A new algorithm for the assignment problem. Mathematical Programming, 21(1):152–171, 1981.