Service Migration Algorithm for Satellite-terrestrial Edge Computing Networks
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摘要: 针对天地一体化边缘计算网络(STECN)的高动态性和复杂性,如何协同优化用户服务延迟与系统迁移成本成为服务迁移算法设计的关键问题。因此,该文提出一种多智能体服务迁移优化(MASMO)算法。首先,考虑到低轨卫星的有限覆盖时间、网络拓扑的动态变化和卫星节点资源等多重因素,对用户服务延迟和系统迁移成本进行建模。其次,将服务迁移优化问题进一步建模为多智能体马尔可夫决策过程(MAMDP)。随后,采用基于轨迹感知的状态信息增强方法,通过融合卫星轨道的可预测信息,引导智能体学习具备前瞻性与稳定性的迁移行为。最后,基于循环多智能体近端策略优化(rMAPPO)算法对服务迁移优化问题进行求解,以最大程度地降低用户服务延迟和系统长期迁移成本。仿真结果表明,所提算法具有良好的收敛性,能够有效协调服务延迟与迁移成本之间的矛盾,对用户服务延迟降低2.90%$ \sim $14.63%的同时,有效降低了系统服务迁移成本11.39%$ \sim $30.57%。
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关键词:
- 天地一体化网络 /
- 服务迁移 /
- 多智能体深度强化学习
Abstract:Objective In highly dynamic Satellite-Terrestrial Edge Computing Networks (STECN), achieving coordinated optimization between user service latency and system migration cost is a central challenge in service migration algorithm design. Existing approaches often fail to maintain stable performance in such environments. To address this, a Multi-Agent Service Migration Optimization (MASMO) algorithm based on multi-agent deep reinforcement learning is proposed to provide an intelligent and forward-looking solution for dynamic service management in STECN. Methods The service migration optimization problem is formulated as a Multi-Agent Markov Decision Process (MAMDP), which offers a framework for sequential decision-making under uncertainty. The environment represents the spatiotemporal characteristics of a Low Earth Orbit (LEO) satellite network, where satellite movement and satellite-user visibility define time-varying service availability. Service latency is expressed as the sum of transmission delay and computation delay. Migration cost is modeled as a function of migration distance between satellite nodes to discourage frequent or long-range migrations. A Trajectory-Aware State Enhancement (TASE) method is proposed to incorporate predictable orbital information of LEO satellites into the agent state representation, improving proactive and stable migration actions. Optimization is performed using the recurrent Multi-Agent Proximal Policy Optimization (rMAPPO) algorithm, which is suitable for cooperative multi-agent tasks. The reward function balances the objectives by penalizing high migration cost and rewarding low service latency. Results and Discussions Simulations are conducted in dynamic STECN scenarios to compare MASMO with MAPPO, MADDPG, Greedy, and Random strategies. The results consistently confirm the effectiveness of MASMO. As the number of users increases, MASMO shows slower performance degradation. With 16 users, it reduces average service latency by 2.90%, 6.78%, 11.01%, and 14.63% compared with MAPPO, MADDPG, Greedy, and Random. It also maintains high cost efficiency, lowering migration cost by up to 14.69% at 12 users ( Fig. 3 ). When satellite resources increase, MASMO consistently leverages the added availability to reduce both latency and migration cost, whereas myopic strategies such as Greedy do not exhibit similar improvements. With 10 satellites, MASMO achieves the lowest service latency and outperforms the next-best method by 7.53% (Fig. 4 ). These findings show that MASMO achieves an effective balance between transmission latency and migration latency through its forward-looking decision policy.Conclusions This study addresses the service migration challenge in STECN through the MASMO algorithm, which integrates the TASE method with rMAPPO. The method improves service latency and reduces migration cost at the same time, demonstrating strong performance advantages. The trajectory-enhanced state representation improves foresight and stability of migration behavior in predictable dynamic environments. This study assumes ideal real-time state perception, and future work should evaluate communication delays and partial observability, as well as investigate scalability in larger satellite constellations with heterogeneous user demands. -
1 MASMO算法
输入:环境状态$ {O}_{t} $ 输出:最优服务迁移策略$ {\pi }_{\theta } $ 1) 初始化actor网络$ {\pi }_{\theta } $与critic网络$ {V}_{\phi } $,初始化经验回放缓冲区
$ D $。2) for 训练迭代次数$ k=1,2,\cdots ,K $do 3) 清空经验回放缓冲区$ D $。 4) 重置并行环境$ e=1,2,\cdots ,{N}_{{\mathrm{env}}} $ 5) for 并行环境$ e=1,2,\cdots, {N}_{{\mathrm{env}}} $ do 6) for $ t=1,2,\cdots ,T $ do 7) 基于局部观测与预测增强特征构造状态$ \boldsymbol{o}_{\mathrm{joint},t} $。 8) 通过执行当前策略$ {\pi }_{\theta } $与环境交互,采集一条经验轨迹
$ {\tau }_{e} $。9) 将轨迹$ {\tau }_{e} $存入经验回放缓冲区$ D $。 10) end for 11) 保存当前策略参数$ {\theta }_{{\mathrm{old}}} $←$ \theta $。 12) 利用critic网络$ {V}_{\phi } $和采集到的数据计算优势估计和$ \hat{A} $回报目
标$\hat {{R}} $。13) for 更新轮次 u=1,2,···,U do 14) 从$ D $中随机抽取n个经验作为一个mini-batch b; 15) 对于 mini-batch $ b $中的每个数据块 $ c $ do 16) 使用数据块首帧的隐藏状态更新$ \pi $和V的RNN状态。 17) 通过最小化损失函数$ L\left(\phi \right) $更新critic参数$ \phi $。 18) 通过最大化目标函数$ J(\theta ) $更新actor参数$ \theta $。 19) end for 20) end for 表 1 参数设置
参数 值 卫星轨道高度$ h $ (km) 212 卫星轨道面倾角(°) 51.67 卫星节点所配备的计算资源 (Gcycles/s) [ 1 000 , 2 000]卫星节点所配备的存储资源(GB) [2, 3] 地面用户坐标经度范围(°) [30, 50] 地面用户坐标纬度范围(°) [100, 135] 最小仰角(°) 30 地面用户请求任务大小(kB) [200, 500] 服务实体大小$ {I}_{e} $ (MB) [300, 500] 任务请求所需要的计算资源 (Gcycle/s) [100, 200] 任务请求所需要的计算强度 (cycle/bit) 106 地面用户设备的发射功率$ {P}_{u} $(W) 5 地面用户到卫星之间的信道带宽 (MHz) 8 地面用户设备天线发射增益 (dBi) 5 卫星天线发射增益 (dBi) 20 卫星天线接收增益 (dBi) 40 实验场景周期 $ T $(s) 600 单个时隙 $ t $ (s) 20 K 4 $ {\omega }_{1},{\omega }_{2} $ 0.6, 0.4 训练轮次 1800 经验回放缓冲区大小 105 学习率lr 5e–5 折扣因子$ \gamma $ 0.95 $ \lambda $ 0.95 mini-batch大小 80 -
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