Li-Fi stands for Light-Fidelity, is a creating department of Optical Wireless Communication (OWC) that gives more noteworthy information transmission using obvious light as a medium rather than conventional radio frequency electromagnetic radiation with the ability to employ surplus users since it uses a wide range of spectrum bandwidth. Recently the implementation of wireless sensors has been increased in the design of high-performance buildings. On the other side, the main challenge in using Wireless Sensor Systems (WSNs) is that the sensor nodes have restricted power in their essential power capacity unit, this power may be rapidly exhausted in case the sensor node remains operational for extended periods of time also data transmission is a significant challenge in WSNs. Non-Orthogonal Multiple Access (NOMA) is a novel encoding technique proposed for next-generation wireless communications. NOMA may send many symbols utilizing the same time, frequency and coding resource but dividing them in the power domain and differentiating them based on the various power levels of distinct symbols, which are subsequently demultiplexed at the receiver using an interference cancellation approach. Since the main requirement of WSNs are high connection, low latency, energy savings, and ultra-high data rates, we give an overview of Li-Fi technology and a study of its performance over WSNs aided by the NOMA technique in this survey article.