OTFS modulation in multi-LEDs indoor VLC setup

Sujata Sinha

I have been working on designing and simulating Orthogonal Space-Time Frequency (OTFS) modulation for Visible Light Communications in an indoor local area network environment. OTFS is 2D signalling technique which effectively tackles the high mobility issues in time varying wireless communications. The setup uses low-cost Light Emitting Diodes (LEDs) and Photodetectors (PD) for transmitters and receivers instead of hardware used in RF communication. The spectrum used is the visible light spectrum (wavelength: 400 - 700 nm) which is available in abundance at no cost, without the need for licensing, no radiation issues and provides inherent security in closed room application. Also, using white light, it can simultaneously be used for data transmission and lightening. In the study to analyse the performance of OTFS in indoor VLC setup using multi-LEDs and multi-PDs (similar to MIMO in RF), we have proposed 4 block transmission schemes using dual-LEDs and quadLED setup, namely, 1) Non-DC biased OTFS (NDC-OTFS), 2) Dual-LED complex modulation OTFS (DCM-OTFS), 3) Quad-LED complex modulation OTFS (QCM-OTFS), and, 4) Spatial modulation dualLED complex modulation OTFS (SM-DCM-OTFS). These schemes have been analysed and compared with their respective OFDM schemes present in the literature. We evaluated their bit error performance and spatial distribution. All the schemes stated above have shown superior performance compared to their OFDM counterparts. The proposed schemes eliminate the use of Hermitian symmetry and DC-bias for transmitting real and non-negative signals suitable to be transmitted through LEDs and thereby, increasing the rates of transmission. This work potentially motivates further research on other possible MIMO VLC architectures using OTFS. Also, this research can help implementation of Network Intelligence systems in wireless networks and networks for smart cities by increasing their cost efficiency and providing security in closed room setup. This work has been accepted for publication in: 1) Sujata Sinha and A. Chockalingam, “OTFS modulation in dual-LED indoor visible light communication systems,”IEEE VTC2021-Fall, September 2021. 2) Sujata Sinha and A. Chockalingam, “Quad-LED OTFS modulation in indoor visible light communication systems,” IEEE GLOBECOM’2021, December 2021