Linear Precoding Designs for MIMO VLC Using Multi-Color LEDs under Multiple Lighting Constraints

Abstract

Multiple-input multiple-output (MIMO) technology as an efficient approach to improve the transmission rate in visible light communication (VLC) has been well studied in recent years. In this paper, we focus on the MIMO VLC system using multi-color LEDs in the typical indoor scenario. Besides the correlation of the MIMO channel, the multi-color crosstalk interference and quadrangle chromaticity region are also considered to increase the practicality of this system. With the constraints of power, amplitude and chromaticity, an iterative algorithm to minimize mean-squared-error (MSE) is proposed to jointly design the precoder and equalizer. Our proposed algorithm provides an effective method to get the optimal precoder by updating optimization variables iteratively. As the equalizer matrix is fixed at each iteration, the main non-convex precoding design problem is transformed into a convex optimization problem and then solved. With the utilization of multi-color LEDs, our proposed precoding method would be promising to promote the practical applications of high-speed indoor optical wireless communication. Simulation results show that our proposed method owns better performance than conventional chromaticity-fixed schemes and zero-forcing precoding designs.

Multi-User Precoder Designs for RGB Visible Light Communication Systems

“…The second one is that forcing spatial zeros becomes more difficult as the number of users in a limited area increases. Finally, the inequalities in (23) and (25) account for a worst-case in which the user's symbols add constructively in the per-LED constraint, and this assumption becomes more pessimistic and challenging as the number of users increases. Therefore, increasing the number of users will constrain the value |w l,d | for each specific user.…”

“…RGB-based systems modify the intensity of the different color LEDs according to the information-bearing signal, for instance, using color Shift Keying (CSK) modulation [17] as in [16,[18][19][20][21][22][23][24]. Other RGB system designs allow the RGB system design to adapt to any target color [25][26][27][28][29][30]. Among previous works, the works in [23,24,26,27] deal with MU scenarios.…”

“…MU precoding has been shown to be a much more efficient approach than TDMA [9] for PWLED-based VLC systems and allows at the same time to keep an independent polar multi-level pulse amplitude modulation (M-PAM) for each user, which may simplify the detection process. In [25], an iterative Mean Square Error (MSE) minimization algorithm is proposed for designing a MIMO precoder and equalizer for single-user scenarios using multi-color LEDs. However, the approach in [25] does not ensure the maximization of the rate or the minimization of the bit error rate, particularly in MU scenarios.…”

“…In [25], an iterative Mean Square Error (MSE) minimization algorithm is proposed for designing a MIMO precoder and equalizer for single-user scenarios using multi-color LEDs. However, the approach in [25] does not ensure the maximization of the rate or the minimization of the bit error rate, particularly in MU scenarios.…”

Advanced LED Solid-State Lighting Optics

“…Related to the multiple-input multiple-output technology as an efficient approach to improve the transmission rate in visible light communication, the paper by Xiao et al [3] focuses on the MIMO VLC system using multi-color LEDs in the typical indoor scenario. Taking the advantages of solid-state lighting, the utilization of multi-color LEDs with the proposed precoding method can promote the practical applications of high-speed indoor optical wireless communication in contrast to the conventional method of chromaticity-fixed schemes and zero-forcing precoding designs.…”