Browsing by Author "Wijesinghe, S. S"

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    Multiuser Access in LiFi using OFDMA
    (IEEE, 2018-10-27) Wijesinghe, S. S; Thilakumara, R. P
    Light Fidelity (LiFi) is an emerging optical technology for wireless data access in short range communication to complement WiFi, a well-established radio frequency (RF) wireless indoor communication standard. Electromagnetic Pollution, relatively low data bandwidths, multipath interference of the indoor propagation to degrade performance, vulnerability to eavesdropping and susceptibility to security threats are major factors that favors LiFi in place of WiFi. However LiFi being an optical technology imposes great difficulty in implementing multiuser access in the Uplink from the user to router. Using Wavelength Division Multiplexing (WDM) for multiuser access drastically increases the cost and complexity of transceivers. This work presents a novel technique of multiuser access using Orthogonal Frequency Division Multiplexing (OFDM) with single carrier per user, implemented by envelope modulation of optical subcarriers for spatially separated users providing compatibility in uplink and downlink of LiFi standard based on OFDM.
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    PAPR Reduction and Multiuser Access using OFDMA for LiFi
    (IEEE, 2020-01-10) Wijesinghe, S. S; Thilakumara, R. P
    Light Fidelity (LiFi) is a novel optical communication technology used in indoor short range wireless communication, competing Radio Frequency (RF) WiFi technology. This technology increases the transmission capacity in indoor propagation while eliminating unwanted Electromagnetic pollution, multipath interference and security threats in RF technology.While OFDMA in LiFi guarantees a more reliable and flexible communication, the peak to average power ratio (PAPR) could impose practical difficulty in designing LiFi OFDM receivers when more subcarriers are added to form the composite OFDM signal due to the need of a larger dynamic range for the receiver. This work presents a novel PWM (Pulse Width Modulated) OFDM approach for Free Space Optical Communication (FSOC) systems that resolves the PAPR problem while providing multiuser access in the uplink from spatially separated users. The energy of the OFDM signal is translated from vertical to horizontal representation using PWM to reduce PAPR problem. This technique can also removes additive noise in propagation by limiting the signal amplitude at the receiver to increase the robustness to noise. This novel method has the potential for very high data rates in short range wireless optical links while providing multiuser wireless access from spatially separate locations.