Browsing Araştırma Çıktıları / WOS by Author "Haas, Harald"
Now showing items 1-6 of 6
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Generalized LED Index Modulation Optical OFDM for MIMO Visible Light Communications Systems
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Publisher and Date:(IEEE, 2016)In this paper we propose a generalized light emitting diode (LED) index modulation scheme for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) visible light communications (VLC) systems. The proposed scheme generalizes the LED index modulation concept by using the spatial multiplexing principle to transmit complex OFDM signals through VLC channels by separating these signals into their real-imaginary and positive-negative parts. The maximum a posteriori (MAP) ...
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A Novel Transmit Array Structure for Optical Spatial Modulation
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Publisher and Date:(IEEE, 2019)The performance of multiple input single output (MISO) and multiple input multiple output (MIMO) systems is limited by spatial channel correlation. This limitation becomes particularly severe in light lidelity (LiFi) systems, which use intensity modulation/direct detection (IM/DD) for data transmission, because light emitting diodes (LEDs) can only emit incoherent light. This paper proposes a novel transmitter structure that provides spatially separated channels and enables optical MISO/MIMO spatial ...
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Optical MIMO-OFDM With Generalized LED Index Modulation
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2017)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 ...
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Physical-Layer Security in Visible Light Communications
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Publisher and Date:(IEEE, 2020)Optical wireless communications (OWC) and its potential to solve physical layer security (PLS) issues are becoming important research areas in 6G communications systems. In this paper, an overview of PLS in visible light communications (VLC), is presented. Then, two new PLS techniques based on generalized space shift keying (GSSK) modulation with spatial constellation design (SCD) and non-orthogonal multiple access (NOMA) cooperative relaying are introduced. In the first technique, the PLS of the ...
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Physical-Layer Security With Optical Generalized Space Shift Keying
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Publisher and Date:(Ieee-Inst Electrıcal Electronıcs Engıneers Inc, 2020)Spatial modulation (SM) is a promising technique that reduces inter-channel interference while providing high power efficiency and detection simplicity. In order to ensure the secrecy of SM, precoding and friendly jamming are widely adopted in the literature. However, neither of those methods can take advantage of SM. In this paper, a novel spatial constellation design (SCD) technique is proposed to enhance the physical layer security (PLS) of optical generalized space shift keying (GSSK), which ...
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Power Control-Based Multi-User Li-Fi Using A Compound Eye Transmitter
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Publisher and Date:(IEEE, 2015)In visible light communications (VLC) the transmitted signal is non-negative and real valued and these characteristics constrain the signal space and provide new challenges for waveform design in a multi-user system. In Light Fidelity (Li-Fi) a VLC technology and similar to radio frequency (RF) systems precoder designs can be used to serve multiple users. However a signal shaping algorithm is required to address the non-negativity of the transmitted signal in Li-Fi. In this study a power allocation ...
