Görülebilir ışık haberleşmesi için kanal modelleme ve karakterizasyonu

Visible light communications (VLC) involve the dual use of illumination infrastructure (i.e., LEDs) for wireless communication purposes. Despite the growing academic and industrial interest, there is a lack of realistic VLC channel models. In the current literature, the models developed for infrared channels in the past are used for the performance evaluation of VLC systems without a solid justification. However, it is known that visible light and infrared bands exhibit different characteristics and this necessitates the development of realistic VLC channel models. In an effort to address this research gap, we present a comprehensive framework for VLC channel modeling and characterization in this thesis. Our channel modeling is based on the ray tracing approach. The simulation environment is created in the Zemax® software and enables us to specify the geometry of the environment, the objects inside, the reflection characteristics of the surface materials as well as the specifications of the light sources and receivers. The received optical power and the delay of direct/indirect rays are computed for the specified indoor environment and the corresponding channel impulse response (CIR) is obtained through proper normalizations. Following this methodology, we present CIRs for a number of indoor environments and quantify channel gain and time dispersion parameters for each environment. We further develop statistical models for characterization of indoor VLC channels through examination of a large set of CIRs collected from thousands of test points in an empty room. Finally, we use the obtained CIRs in the error rate performance evaluation of various operation modes in the IEEE 802.15.7 VLC standard.