Hadamard Matrix Design for a Low-Cost Indoor Positioning System in Visible Light Communication

Abstract

A positioning system based on visible light communication (VLC) utilizes illuminating indoor lights to identify the location of objects. The complexity and the cost of VLC are largely affected by limited bandwidths on optical emitters and detectors. In this paper, we present an optical signaling and multiplexing technique, which employs Hadamard matrices to implement a multiple-input multiple-output (MIMO) system. Fundamental conditions to create nonnegative optical signals and brightness control are defined in conjunction with multiplexing different sources and receiving messages. By using two design methods n-1 and M constructions, Hadamard matrices can be used to implement MIMO VLC without considering bandwidth limits for emitters or receivers. Eventually, the presented model and the method generalize multiplexing techniques with orthogonality from a view of orthogonal matrices. Experiments show that the proposed positioning system has 0.02-m standard errors of identification due to the noise component in a slow optical receiver.

Keywords

• Visible light communication (VLC)
• indoor positioning
• indoor localization
• light emitting diode (LED)
• photodetector
• Hadamard matrix