Exploiting Polarization and Color to Enable MIMO Backscattering with Light

Multiple-input multiple-output (MIMO) methods play a pivotal role in increasing the capacity of wireless communication systems, but they have not been analyzed systematically in the nascent area of passive communication with visible light (passive-VLC). The main challenge in passive-VLC is its low data rate. This limitation is caused by the slow switching speed of the most popular modulator used in the state-of-the-art: liquid crystal cells (LCs). Several studies use sophisticated modulation schemes with multiple LCs to increase the data rate. However, these efforts have only led to logarithmic improvements. A transmitter with a single LC can provide 1 kbps, and a transmitter with 64 LCs delivers 8 kbps: resulting in an efficiency of 125 bps per LC cell. Ideally, the capacity should increase linearly with the number of LCs.