Browsing by Author "Mamus, Atilla"

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Analysis of Visible Light Communation Sytems and Adaptive Equalization Effects
(Kadir Has Üniversitesi, 2015) Mamus, Atilla; Panayırcı, Erdal; Panayırcı, Erdal
Communication by means of visible light is a newly developing technology that has been brought up as an alternative to the current electromagnetic based communication systems. The recently conducted studies led to the use of LED Technology for illumination purposes and for this technology to have an edge over devices that consume excessive energy as presently being used by us. LED technology is predicted to become an important part of illumination systems especially in consideration of the low energy consumption low voltage use product longevity and small size the technology can provide. Furthermore the use of semi-conductor materials in the LED technology lends this illumination tool the capability to be turned on and off very fast in comparison to the other similar purpose devices. This capability makes it possible for LED technology to be used as a means of data transmission in addition to being a means of illumination. Studies are being conducted to use LEDs effectively as an optic transmission transmitter antenna and application of modulation techniques used in electromagnetic systems to VLC technology for purposes of achieving resistance against white noise reflections refractions and echoes. in literature the model of receiving data by means of adaptive filters and its processing has been used in very limited number of studies and in these studies generally LMS algorithms were used. in this dissertation an empty room in rectangular prism shape in pre-determined dimensions was used with LED panels in numbers and positions previously determined which sent data whereby the impulse response displayed by the channel until the data sent that reached the photo detector was analyzed according to different FOV angles in computer environment and later on the data was sent to the receiver through these channels that have differing impulse response based on specific FOV degrees. The data that is processed at the receiver was passed through adaptive filters to evaluate byte error rate performances in the computer environment. LMS and RLS algorithms were used in the adaptive filter. The simulation results have been displayed in graphics of bit error rate change based on SNR and it has been observed that the adaptive filter on which RLS algorithm is used provided better results than the adaptive filter on which LMS algorithm was used. bstract.
Modeling and Equalization of Indoor Visible Light Channnels
(IEEE, 2016) Mamus, Atilla; Panayırcı, Erdal; Yeşilkaya, Anıl; Panayırcı, Erdal
In this paper a computationally efficient method is proposed for modeling the indoor visible light communications (VLC) channels using a non-sequential ray tracing technique. We created three dimensional realistic simulation environment to depict indoor scenarios specifying the geometry of the indoor environment the objects inside the reflection characteristics of the surface materials as well as the characteristics of the transmitter and receiver. We then compute the received optical power and the delay of direct/indirect rays which are used to obtain the channel impulse response (CIR). Finally LMS (least mean squares) and RLS (recursive least squares) iterative channel equalization techniques which are wildly employed in traditional electrical wireless communications are tested at the receiver of the VLC system. Their convergence rates as well as impacts on the BER performances are investigated by determining the optimal control parameters of these algorithms. It is concluded that for the equalizer operating with its optimal parameters the BER performances of the VLC systems are very sensitivie to the field of view (FOV) values.