室内VLC异构网络接入与切换方法研究

As an emerging wireless optical communication technology, visible light communication (VLC) has extensive application prospects because of the advantages of high-capacity, anti-electromagnetic interference, free spectrum application and green energy-saving. However, if used for communication singly, VLC has many shortcomings. For instance, the modulation bandwidth of LED is limited; the communication link is easy to be blocked; the multi-path effect is remarkable; and the uplink is difficult to implement etc..Heterogeneous network fused by VLC and other wireless access technology can significantly increase the system capacity and resource utilization, which keeps up with the trend of the 5G..To realize indoor heterogeneous network based on VLC, the best initial access and reliable dynamic handoff are necessary. Aiming at the problem of initial access, a re-weighting method based on multiple attribute decision making (MADM) is proposed to achieve optimal network selection from multiple candidate networks. The re-weighting method can not only satisfy the user’s preference, but also avoid the subjectivity of weight distribution. Meanwhile, a threshold virtual handoff algorithm based on CSMA/CA is proposed to avoid the excessive access delay. The key problem of dynamic handoff is also studied in this project, EC-KPA prediction algorithm is proposed, and then multi-attribute dynamic handoff method based on motion state is also proposed to ensure the quality of service (QoS). In order to construct a more reliable network, an indoor VLC multiple access method based on the backoff mechanism is studied to solve the problem of uplink access collision; Moreover, optical codes suitable for indoor VLC system is designed to eliminate downlink information interference.

可见光通信（VLC）是新兴无线通信技术，其大容量、抗电磁干扰、免频谱申请、绿色节能的优势有广泛的应用前景。作为单一的无线通信方式，VLC存在调制带宽有限、链路易被遮挡、多径效应明显、上行难以实现等诸多缺陷。融合VLC与其它无线接入技术的异构网络可显著提升系统容量和资源利用率，顺应5G时代潮流。实现基于VLC的室内异构网络需要最优的初始化接入和可靠的动态切换。针对最优初始化接入，本项目提出二次加权多属性判决方法以实现候选网络的网络择优，既实时满足用户偏好，又避免权重分配有强烈主观性；同时，提出基于CSMA/CA的门限虚切换算法，避免接入时延过大。针对动态切换，提出EC-KPA预测算法，进而研究提出基于运动状态的多属性动态切换方法，保证服务质量。为了更可靠地实现网络建连，本项目提出基于退避机制的室内VLC多址接入方法，解决上行接入碰撞；同时，设计适合室内VLC系统的光地址码，消除下行信息干扰。

可见光通信（VLC）作为新兴通信技术，其大容量、抗电磁干扰、节约能耗的优势有广泛的应用前景。但是VLC同时也存在调制带宽有限、链路易被遮挡、上行难以实现等缺点。融合VLC与红外通信、射频通信等技术的异构网络可显著提升系统容量和资源利用率。.本项目的研究思路是基于用户在VLC异构网中的服务过程，具体的研究内容包括：VLC信道建模、异构网络中的网络择优和切换策略、多址接入和干扰消除技术、无线光通信的基础理论等。首先，考虑到VLC信息传输主要通过视距链路，本研究讨论了室内存在多个遮挡物体时的系统性能，给出了对阴影位置、面积及影响的准确模拟，发表相关论文2篇；其次，针对最优初始化接入，本项目提出二次加权多属性判决方法以实现候选网络的网络择优思路，既实时满足用户偏好，又避免权重分配有强烈主观性，发表相关论文2篇；接着，研究团队提出基于CSMA/CA的门限虚切换算法，避免接入时延过大，针对动态切换，提出EC-KPA预测算法，进而研究提出基于运动状态的多属性动态切换方法，保证服务质量，发表相关论文2篇；随后，研究了室内VLC/异构网络中的多址接入和下行信号干扰消除技术，充分考虑人眼安全、系统功率有限等实际约束，给出最优的功率和资源分配方案，发表相关论文4篇；同时，本项目研究了光网络在自然灾害等场景中的应用前景，讨论了协同存储系统的容灾服务供应问题，发表相关论文1篇；最后，团队同时对光通信的相关基础理论也展开了研究，包括光电子器件设计、编码方式设计及微波光子理论研究等，发表多篇相关论文。此外，项目团队也储备了相关专利，目前已获授权7项。.总体来说，本项目以VLC/异构网络为核心，充分了调研行业动态，研究了网络构建和使用过程中的多个关键问题，提出了多种技术路径和解决方案，建立了较为完善的理论体系，为光通信及VLC领域培养了多名人才，为今后的研究提供了一定的理论支撑和实验依据。