Visible light communications (VLC) is a promising and uncharted new technology for the next generation of wireless communication systems. This paper proposes a novel generalized light emitting diode (LED) index modulation method for multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) based VLC systems. The proposed scheme avoids the typical spectrum efficiency losses incurred by time and frequency domain shaping in OFDM signals. This is achieved by exploiting spatial multiplexing along with LED index modulation. Accordingly, real and imaginary components of the complex time domain OFDM signals are separated first, then resulting bipolar signals are transmitted over a VLC channel by encoding sign information in LED indexes. As a benchmark, we demonstrate the performance analysis of our proposed system for both analytical and physical channel models. Furthermore, two novel receiver designs are proposed. Each one is suitable for frequency-flat or selective channel scenarios. It has been shown via extensive computer simulations that the proposed scheme achieves considerably better bit error ratio (BER) vs. signal-tonoise-ratio (SNR) performance than the existing VLC-MIMO-OFDM systems that use the same number of transmit and receive units (LEDs and photo diodes (PDs)). Compared with the singleinput single-output (SISO) DC biased optical OFDM (DCO-OFDM) system, both spectral efficiency and DC bias can be doubled and removed respectively simply by exploiting a MIMO configuration.

Spatial modulation (SM) has proven to be a promising multiple-input-multiple-output (MIMO) technique which provides high energy efficiency and reduces system complexity. In SM, only one transmitter is active at any given time while the rest of them remain silent. The index of the active transmitter carries information. This spatial information is in addition to the data carried by the constellation symbols in the signal domain. Therefore, SM increases the transmission rate of the communication system compared to single-input-single-output and space-time block coding (STBC)-MIMO. For signal domain data encoding, orthogonal frequency division multiplexing (OFDM) has been widely adopted. The key benefits in multi-carrier intensity-modulation and direct-detection (IM/DD) systems are: i) the capability to achieve high spectral efficiency and ii) the ability to effectively mitigate direct-current (DC) wander effects and the impact of ambient light. However, current off-theshelf light emitting diodes (LEDs) which are used as transmit entities are primarily bandwidth limited. Thus, there are benefits of combining SM and OFDM to enhance transmission speeds while maintaining low complexity. In this paper, the two most common OFDM-based SM types, namely frequency domain SM (FD-SM) and time domain SM (TD-SM), are investigated for optical wireless communications (OWC). Moreover, proof-ofconcept experimental results are presented to showcase practical feasibility of both techniques. The obtained results are also compared with Monte Carlo simulations. The results show that TD-SM with an optimal maximum-a-posteriori-probability (MAP) detector significantly outperforms FD-SM. It can be inferred from the results that TD-SM is a strong candidate among OFDMbased optical SM systems for future optical IM/DD wireless communication systems.

No abstract

The future of the manufacturing industry highly depends on digital systems that transform existing production and monitoring systems into autonomous systems fulfilling stringent requirements in terms of availability, reliability, security, low latency, and positioning with high accuracy. In order to meet such requirements, private 5G networks are considered a key enabling technology. In this paper, we introduce the 5G-CLARITY system that integrates 5G new radio (5GNR), Wi-Fi and light fidelity (LiFi) access networks, and develops novel management enablers to operate 5G-Advanced private networks. We describe three core features of 5G-CLARITY including a multi-connectivity framework, a high precision positioning server and a management system to orchestrate private network slices. These features are evaluated by means of packet level simulations and an experimental testbed demonstrating the ability of 5G-CLARITY to police access network traffic, to achieve cm-level positioning accuracy, and to provision private network slices in less than one minute.