室内VLC异构网络接入与切换方法研究

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。

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.