Adaptive Sending Duration Algorithm and Memory Decoding of Non-linear LED Response

Due to the limitation of radio frequency (RF) spectrum, it is increasingly more difficult to support billions of wireless devices in the age of Internet-of-Things. Consequently, many recent wireless indoor communication systems have been developed using free space optical (FSO) communication technologies that exploit a large spectrum of light to transmit data. However, FSO technologies, especially when using On-Off Keying modulation, the Light-Emitting-Diode (LED) transmitters produce an inherent non-linear distortion in the output. Effectively, the LED acts a low-bandwidth channel between the inputs and outputs. In this paper, we develop (1) a mathematical model for the distortion, (2) a pre-distortion algorithm called Adaptive Sending Duration Algorithm (ASDA) that modifies the input duration in order to compensate for the distortion at the output, and (3) a post-distortion algorithm which is a memory decoding method that exploits the distortion model to reduce the error rates. Both theoretical analyses and simulation results show that the proposed algorithms outperform the conventional methods such as linear equalization techniques.

Major Advisor: Thinh Nguyen
Minor Advisor: Liang Huang
Committee: Bella Bose
Committee: Alan Wang
GCR: Leonard Coop