Browsing by Author "Sarbazi, Elham"

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    Master ThesisPublicationMetadata only
    Channel modelling and characterization for visible light communications
    (2014-08) Sarbazi, Elham; Uysal, Murat; Demiroğlu, Cenk; Aldırmaz, S.; Department of Electrical and Electronics Engineering; Sarbazi, Elham
    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.
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    Indoor channel modelling and characterization for visible light communications
    (IEEE, 2014) Sarbazi, Elham; Uysal, Murat; Abdallah, M.; Qaraqe, K.; Electrical & Electronics Engineering; UYSAL, Murat; Sarbazi, Elham
    In this paper, we investigate channel modeling for visible light communications using ray tracing approach. The simulation environment is created in Zemax® 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 multipath channel parameters gain for each environment.
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    Conference paperPublicationMetadata only
    PHY layer performance evaluation of the IEEE 802.15.7 visible light communication standard
    (IEEE, 2013) Sarbazi, Elham; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Sarbazi, Elham
    The IEEE 802.15.7 standard defines a PHY layer and medium access control (MAC) layer for visible light communication and promises data rates sufficient to support audio and video multimedia services. In this paper, we first provide an overview of different PHY types available in the IEEE 802.15.7 standard, then present an extensive comparative error rate performance evaluation of PHY I, II and III types through Monte Carlo simulations.
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    Ray tracing based channel modeling for visible light communications
    (IEEE, 2014) Sarbazi, Elham; Uysal, Murat; Abdallah, M.; Qaraqe, K.; Electrical & Electronics Engineering; UYSAL, Murat; Sarbazi, Elham
    Bu bildiride, Zemax 13 yazılımı aracılığı ile görünür ışık haberleşmesi (visible light communication, VLC) kanalları karakterize edilecektir. Yaklaşımımızda, ölçülerini tanımlayacağımız iç mekân ortamı üçboyutlu olarak Zemax’da oluşturulmakta ve LED tabanlı ışık kaynakları uygun noktalara yerleştirilmektedir. Söz konusu yazılımım ışın izleme (ray tracing) araçları kullanılarak, alıcı tarafa doğrudan ve dolaylı yollardan (yansımalar) ulaşan sinyallerin gücü ve gecikme süreleri hesaplanmaktadır. Daha sonra bu bilgiler Matlab’a aktarılarak uygun normalleştirmeler aracılığı ile bu iç mekan propagasyonu ortamına karşılık gelen kanal dürtü cevabı elde edilmektedir. Bu yöntem izlenerek, değişik ebatlardaki odalarda farklı alıcı/verici yerleşimleri varsayımları altında kanal dürtü cevapları elde edilmiş ve gecikme yayılımı, DC kazancı vb kanal parametreleri hesaplanmıştır.