Impact of Multipath Reflections on the Performance of Indoor Visible Light Positioning Systems (1505.07534v1)

Abstract: Visible light communication (VLC) using light-emitting-diodes (LEDs) has been a popular research area recently. VLC can provide a practical solution for indoor positioning. In this paper, the impact of multipath reflections on indoor VLC positioning is investigated, considering a complex indoor environment with walls, floor and ceiling. For the proposed positioning system, an LED bulb is the transmitter and a photo-diode (PD) is the receiver to detect received signal strength (RSS) information. Combined deterministic and modified Monte Carlo (CDMMC) method is applied to compute the impulse response of the optical channel. Since power attenuation is applied to calculate the distance between the transmitter and receiver, the received power from each reflection order is analyzed. Finally, the positioning errors are estimated for all the locations over the room and compared with the previous works where no reflections considered. Three calibration approaches are proposed to decrease the effect of multipath reflections.

• The paper demonstrates that multipath reflections significantly degrade VLC positioning accuracy, especially in peripheral indoor regions.
• The paper employs a hybrid CDMMC simulation method combining deterministic and Modified Monte Carlo techniques to model indoor light reflections.
• The paper proposes calibration methods, including TDM signal access, nonlinear estimation, and dense LED layouts, to mitigate reflection-induced errors.

Impact of Multipath Reflections on the Performance of Indoor Visible Light Positioning Systems

The paper "Impact of Multipath Reflections on the Performance of Indoor Visible Light Positioning Systems" explores the technical challenges and solutions related to positioning systems utilizing visible light communication (VLC). The paper focuses on understanding how multipath reflections, a prevalent issue in indoor environments, affect the accuracy of visible light positioning systems using LEDs as transmitters.

VLC is presented as a promising technology for enabling indoor positioning, especially in situations where traditional GPS signals are ineffective due to signal attenuation by physical structures. In the proposed VLC-based system, LEDs are used to transmit positioning information, which is then detected by a photo-diode (PD) that analyzes received signal strength (RSS) to determine the location. The research implements a Combined Deterministic and Modified Monte Carlo (CDMMC) method to simulate impulse responses of the optical channel, offering insights into how signals reflect off walls, ceilings, and floors, thereby causing distortion and impacting positioning accuracy.

Important Technical Methodologies

1. CDMMC Method: The paper uses a hybrid approach combining deterministic and Modified Monte Carlo techniques. Each method contributes uniquely by computing first-order reflections with high precision and employing Monte Carlo simulations for subsequent reflections to improve computational speed.
2. Time Division Multiplexing (TDM) for Signal Access: TDM is employed to prevent interference between signals from different LED transmitters by synchronizing their transmission times.
3. Distance Calculation: The distance between transmitter and receiver is calculated using derived power attenuation formulas, facilitating the estimation of horizontal receiver coordinates through a least square estimation algorithm.

Key Findings and Implications

The results indicate that multipath reflections notably impair positioning accuracy, particularly in the outer regions of the room where reflection components significantly contribute to received signal strength. Quantitative analysis reveals considerable discrepancies between positioning errors when reflections are excluded versus included. The paper calculates positioning errors across various room sections and effectively demonstrates the degradation of system performance due to multipath effects.

Calibration Approaches

To mitigate these inaccuracies, several calibration methodologies are introduced:

• Nonlinear Estimation: A refined positioning algorithm is proposed using nonlinear approaches instead of linear estimation, aiming to minimize Euclidean distance discrepancies.
• Signal Selection and Dense LED Layouts: By selectively using the strongest signals and reducing the spatial distance between LED bulbs, the system enhances positioning precision, reducing the impact of multipath reflections.

Future Directions

The findings from this investigation point towards promising avenues for research and improvement in VLC positioning systems. Future studies could explore optimizing LED arrangements and signal modulation to further reduce reflection interference. Emphasis on the development of adaptive algorithms that can autonomously switch calibration strategies based on environmental data and refine impulse response calculations could present a substantial leap forward in the fidelity of VLC-based positioning technologies.

Overall, this research contributes significantly to understanding and overcoming the challenges posed by multipath reflections in VLC systems, paving the way for more reliable indoor positioning solutions, which are crucial for numerous applications in smart environments and IoT frameworks.