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To solve the above challenges, we propose a distributed fairness-guided handover strategy (DHO-F) to dynamically select the best HO target and sub-channel. Specifically, the DHO-F optimization problem is formulated based on max-min egalitarian fairness and further modeled as a multi-objective Markov decision process (MOMDP), where fairness is expressed by the social welfare function (SWF). To address MOMDP, the analytical form of the policy gradient to maximize fairness is derived. Subsequently, Multi-agent Proximal Policy Optimization (MAPPO) with distributed cooperation is exploited to achieve long-term maximization. The fairness-guided MAPPO (FG-MAPPO) features a hybrid network architecture that simultaneously takes into account maximizing individual link rates and fairness among UEs. It reconciles these two conflicting objectives through the collaboration between a throughput-oriented (TO) network and a fairness-oriented (FO) network. Additionally, a distributed training framework is implemented to improve the sample efficiency and data diversity for on-policy FG-MAPPO. FG-MAPPO is fully compatible with 3GPP\u2019s conditional handover (CHO) framework, demonstrating that it can be implemented in real-world. Extensive evaluations demonstrate that DHO-F demonstrates superior performance even compared to centralized algorithms, achieving an average improvement of 3.48% in SWF metric. Moreover, DHO-F establishes new SOTA performance in balancing fairness and rate maximization across medium-to-high load scenarios compared to IDQN, ISAC, and MAPPO.<\/jats:p>","DOI":"10.1145\/3760527","type":"journal-article","created":{"date-parts":[[2025,8,13]],"date-time":"2025-08-13T11:15:01Z","timestamp":1755083701000},"page":"1-30","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Incentivizing Cooperation for Handover Strategies in LEO Constellations via Fairness-guided MARL"],"prefix":"10.1145","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-5237-8283","authenticated-orcid":false,"given":"Xiupu","family":"Lang","sequence":"first","affiliation":[{"name":"School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University - Minhang Campus","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-7684-1065","authenticated-orcid":false,"given":"Lin","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Electronic Information and Electronic Engineering, Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-8628-6750","authenticated-orcid":false,"given":"Peiqi","family":"Huang","sequence":"additional","affiliation":[{"name":"SJTU Paris Elite Institute of Technology, Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-0149-8705","authenticated-orcid":false,"given":"Jinming","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-5159-6256","authenticated-orcid":false,"given":"Boming","family":"Zhu","sequence":"additional","affiliation":[{"name":"Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-6052-1434","authenticated-orcid":false,"given":"Xiaojian","family":"Gao","sequence":"additional","affiliation":[{"name":"Reins, Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3452-3347","authenticated-orcid":false,"given":"Lin","family":"Gui","sequence":"additional","affiliation":[{"name":"Shanghai Jiao Tong University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4535-5038","authenticated-orcid":false,"given":"Haopeng","family":"Chen","sequence":"additional","affiliation":[{"name":"Shanghai Jiao Tong University","place":["Shanghai, China"]}]}],"member":"320","published-online":{"date-parts":[[2026,1,15]]},"reference":[{"key":"e_1_3_2_2_2","unstructured":"[n.d.]. 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