Optimizing power allocation for LED-based distributed-MIMO OWC systems

The Internet is not only accessed by computers and smartphones. With the rise to the Internet-of-Things (IoT), a very wide variety of smart objects can be connected to the network. Today, there are already billions of wearables, sensors, televisions, medical and industrial machines, and other devices transmitting and receiving information through the network. To achieve better management of interference among nearby RF access points, and to densify the system, research in radio frequency (RF) technologies has moved towards to the use of shorter wavelengths, thereby achieving very small cells. Extending the choice of higher carrier frequencies further, optical wireless communications has also attracted more and more attention. To accelerate mass market adoption, LiFi system designers have considered the use of inexpensive light-emitting diodes (LED)s. However, some challenges must be overcome for designing high-speed data transmission systems using them, such as their low-pass effect. Besides that, LEDs are anyhow limited in power. To exploit its best performance and provide reliable signal transmission for a long time, their power limitation must be respected. The simultaneous transmission of multiple signals through multiple emitters and multiple receivers using multiple-input multiple-output (MIMO) schemes help to improve performance against the low-pass channel by exploring the MIMO multiplex gain. Using orthogonal-frequency-division-multiplexing (OFDM), multiple independent subcarriers are simultaneously transmitted over the low-pass frequency response of every LED. OFDM allows the use of power loading strategies for finding the best power-spectrum density for throughput improvement . This paper gives an overview on recent results and an outlook towards improved power allocation algorithms for LED-based D-MIMO OWC systems