Joint communication and indoor positioning based on visible light in the presence of dimming

This paper proposes a joint communication and indoor positioning (JCP) system based on visible light communication (VLC) designed for indoor environments. The framework supports 2D and 3D positioning using received signal strength (RSS) from pilot transmissions, enhanced by the radical axis theorem to improve accuracy under measurement uncertainties. Communication is achieved using spatial modulation (SM) with M-ary pulse amplitude modulation (PAM), where data is conveyed through the modulation symbol and the active light-emitting diode (LED) index, improving spectral efficiency while maintaining low complexity. A pilot-aided least squares (LS) estimator is employed for joint channel and dimming coefficient estimation, enabling symbol detection in multipath environments characterized by both line-of-sight (LOS) and diffuse non-line-of-sight (NLOS) components, modeled using Rician fading. The proposed system incorporates a dimming control mechanism to meet lighting requirements while maintaining reliable communication and positioning performance. Simulation results obtained under the adopted system settings and Rician fading channel assumptions demonstrate sub-centimeter localization accuracy at high SNRs and bit error rates (BERs) below 10⁻⁶ for low-order PAM schemes. The results reveal a location-dependent tradeoff between positioning and communication performance. Positioning accuracy is maximized near the geometric center of the LED layout, while communication reliability is higher at off-center locations due to the asymmetric channel geometry producing a better-conditioned channel matrix for spatial modulation detection. These simulation-based findings demonstrate the potential of the proposed framework as a candidate solution for future 6G indoor networks requiring integrated localization and communication.