Time Multiplexed Optical-OFDMA for Uplink Transmission in LiFi-based IoT Networks

The transfer of data from multiple internet of things (IoT) devices requires the use of a robust and efficient multiple access (MA) solution. This paper considers the orthogonal frequency division MA (OFDMA) technique for the light-fidelity (LiFi)-based IoT uplink using infrared to transmit data from multiple mobile users to a fixed access point. The conventional schemes based on orthogonal frequency allocate distinct subcarriers to each user sharing the same time slot. We consider a new approach by allocating distinct time slots to a group of OFDMA users. Taking into account realistic opto-electronic components, we study the performance of the conventional and proposed optical-OFDMA schemes. We show that asymmetrically clipped optical-OFDMA signaling scheme outperforms direct current biased signaling in terms of electrical power efficiency. Focusing on the asymmetrically clipped signaling, We demonstrate the robustness of our proposed time multiplexed optical-OFDMA scheme against MA interference caused by signal clipping. We also show the advantages of our scheme in reducing computational complexity by a factor of 2 compared to the conventional optical-OFDMA schemes.