Browsing by Author "Zhang, Haijun"

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    Multi-agent DRL for resource allocation and cache design in terrestrial-satellite networks
    (IEEE, 2022-12-29) Li, Xiaonan; Zhang, Haijun; Zhou, Huan; Wang, Ning; Long, Keping; Al-Rubaye, Saba; Karagiannidis, George K.
    In the past few years, satellite communications have greatly affected our daily lives, and the integrated terrestrial-satellite network can combine the advantages of satellite and base stations (BSs) to provide wider coverage and lower cost. Because the resources of terrestrial-satellite network are limited, how to allocate resources of terrestrial-satellite network through effective methods has become a major challenge. This paper proposes a framework for resource allocation of terrestrial-satellite network based on non-orthogonal multiple access (NOMA). Then, a deployment method of local cache pools is given to achieve lower time delay and maximize energy efficiency in terrestrial-satellite network. In the proposed framework, we adopt a multi-agent deep deterministic policy gradient (MADDPG) method to obtain the maximum energy efficiency by user association, power control, and cache design. The MADDPG algorithm is divided into two stages, users and BSs are set as agents to complete the optimization problem in the framework. Finally, the simulation results show that the proposed method has better optimized performance compared with the traditional single-agent deep reinforcement learning algorithm and can efficiently solve the problems of resource allocation and cache design in the integrated terrestrial-satellite network.
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    Ultra dense satellite-enabled 6G networks: Resource optimization and interference management
    (IEEE, 2023-05-10) Liu, Xiangnan; Zhang, Haijun; Sheng, Min; Li, Wei; Al-Rubaye, Saba; Long, Keping
    With the evolution of the sixth generation (6G) mobile communication technology, ample attention has gone to the integrated terrestrial-satellite networks. This paper notes that four typical application scenarios of integrated terrestrial-satellite networks are integrated into ultra dense satellite-enabled 6G networks architecture. Then the subchannel and power allocation schemes for the downlink of the ultra dense satellite-enabled 6G heterogeneous networks are introduced. Satellite mobile edge computing (SMEC) with edge caching in three-layer heterogeneous networks serves to reduce the link traffic of networks. Furthermore, a scheme for interference management is presented, involving quality-of-service (QoS) and co-tier/cross-tier interference constraints. The simulation results show that the proposed schemes can significantly increase the total capacity of ultra dense satellite-enabled 6G heterogeneous networks.