Efficient Signal Processing in OFDM-based Indoor Optical Wireless Links

Abstract

We propose a rate-adaptive optical wireless transmission system based on orthogonal frequency division multiplexing for indoor communications. The investigations rely on realistic parameters of the key system components and focus on throughput maximization. We will show that a dynamically adaptive system can greatly enhance performance when compared to static operation, and how a loading algorithm, which optimally performs in powerlimited systems, needs to be adjusted if the specific terms of the optical wireless channel are to be rigorously obeyed. Our investigations include scenarios in which the non-negativity constraint on the optical source driving signal is strictly met and in which a certain amount of symmetric clipping is tolerated. In the latter case, the system can be regarded as power-limited and conventional loading algorithms are hence the most suitable. We will show that the transmission rate can be significantly improved even further by accepting a minor increase in the error rate as a result of controlled clipping, and we will compare our results with the upper system capacity limit.