Browsing by Author "Yesilkaya, A."

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Placeholder
    ArticlePublicationMetadata only
    Optical MIMO-OFDM with generalized LED index modulation
    (IEEE, 2017-08) Yesilkaya, A.; Basar, E.; Miramirkhani, Farshad; Panayirci, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
    Visible light communications (VLC) is a promising and uncharted new technology for the next generation of wireless communication systems. This paper proposes a novel generalized light emitting diode (LED) index modulation method for multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM)-based VLC systems. The proposed scheme avoids the typical spectrum efficiency losses incurred by time- and frequency-domain shaping in OFDM signals. This is achieved by exploiting spatial multiplexing along with LED index modulation. Accordingly, real and imaginary components of the complex time-domain OFDM signals are separated first, then resulting bipolar signals are transmitted over a VLC channel by encoding sign information in LED indexes. As a benchmark, we demonstrate the performance analysis of our proposed system for both analytical and physical channel models. Furthermore, two novel receiver designs are proposed. Each one is suitable for frequency-flat or selective channel scenarios. It has been shown via extensive computer simulations that the proposed scheme achieves considerably better bit error ratio versus signal-to-noise-ratio performance than the existing VLC-MIMO-OFDM systems that use the same number of transmit and receive units [LEDs and photo diodes (PDs)]. Compared with the single-input single-output (SISO) DC biased optical (DCO)-OFDM system, both spectral efficiency and DC bias can be doubled and removed respectively simply by exploiting a MIMO configuration.
  • Placeholder
    Conference paperPublicationMetadata only
    Performance of MIMO enhanced unipolar OFDM with realistic indoor visible light channel models
    (IEEE, 2016) Yesilkaya, A.; Miramirkhani, Farshad; Basar, E.; Panayirci, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
    Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems, realistic indoor optical channel modeling becomes an important issue to be handled. In this paper, first we obtain new realistic indoor VL channel characterizations and models, in a multipleinput multiple-output (MIMO) transmission scenario, using nonsequential ray tracing approach for the channel impulse responses (CIRs). Practical issues such as number of light emitting diode (LED) chips per luminary, spacing between LED chips, objects inside the room and cabling topology are also investigated. On the other hand, since indoor optical channels exhibit frequency selectivity, multi-carrier communication systems, particularly orthogonal frequency division multiplexing (OFDM) is used to handle the resulting inter-symbol interference in VLC systems. Hence, we propose a new MIMO-OFDM based VLC system, called MIMO enhanced unipolar OFDM (MIMOeU-OFDM) by combining MIMO transmission techniques with the recently proposed eU-OFDM scheme. The bit error rate (BER) performance of the proposed system is investigated in the presence of the 2 × 2 and 4 × 4 realistic MIMO VLC channels and its BER performance is compared with the reference optical MIMO-OFDM systems.
  • Placeholder
    Conference paperPublicationMetadata only
    Performance of MIMO enhanced unipolar OFDM with realistic indoor visible light channel models
    (IEEE, 2016) Yesilkaya, A.; Miramirkhani, Farshad; Basar, E.; Panayirci, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
    Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems, realistic indoor optical channel modeling becomes an important issue to be handled. In this paper, first we obtain new realistic indoor VL channel characterizations and models, in a multiple-input multiple-output (MIMO) transmission scenario, using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical issues such as number of light emitting diode (LED) chips per luminary, spacing between LED chips, objects inside the room and cabling topology are also investigated. On the other hand, since indoor optical channels exhibit frequency selectivity, multi-carrier communication systems, particularly orthogonal frequency division multiplexing (OFDM) is used to handle the resulting inter-symbol interference in VLC systems. Hence, we propose a new MIMO-OFDM based VLC system, called MIMO enhanced unipolar OFDM (MIMO-eU-OFDM) by combining MIMO transmission techniques with the recently proposed eU-OFDM scheme. The bit error rate (BER) performance of the proposed system is investigated in the presence of the 2 × 2 and 4 × 4 realistic MIMO VLC channels and its BER performance is compared with the reference optical MIMO-OFDM systems.