This paper reports on the first real-time implementation of reliable optical wireless communications in an field programmable gate array and laboratory trials using the high-bandwidth physical layer defined in IEEE Std 802.15.13-2023. Orthogonal frequency-division multiplexing with adaptive bitloading is implemented in real-time to adapt the link to time-varying channel conditions. Clipping is used to increase the transmission range. Optical front-ends are made of multiple, off-the-shelf high-power light-emitting diodes and large-area photodiodes which enable ranges of several meters for short-range mobile applications. High reliability is observed in a point-to-point scenario. Packet error rates of 3 • 10−7and a peak throughput of 599.2 Mbit/s are measured. Error-free real-time operation is demonstrated for a series of 108packets at distances up to 3.5 m.

An increasing number of industrial Internet-ofthings applications requires wireless transmission of control and data packets. A combination of optical wireless communication (also denoted as LiFi), for deterministic wireless access, and powerline communication, as a cost-effective backbone, is considered promising to enable easy installation of small wireless cells. This paper reports on work in progress from an initial measurement campaign to characterize the cascaded LiFi-over-powerline link in physical layer. The combined channel and noise have been studied in a practical setup for the first time. The frequency response was measured up to 100 MHz under various channel conditions to capture multi-path and attenuation effects across different cable lengths and free-space distances. Also, interference and noise were evaluated up to 300 MHz, revealing contributions from both the PLC and LiFi segments.

Light Fidelity (LiFi) networks transmit information via light waves and are an interesting alternative to Radio Frequency networks: as light can be confined easily, LiFi provides better performance and makes eavesdropping attacks much more difficult. A core application of LiFi networks is self-contained and local networks among a group of autonomous devices, e.g., in industrial or medical environments. Cryptographic protocols are used to secure these networks, however the key exchange sometimes relies solely on the confineability of light signals and sends key material in plain over the network. This is clearly not desirable from a security perspective and newer standards recommend key exchange protocols to establish shared keys. A crucial part in any authenticated key exchange protocol is how to bootstrap trust, e.g., by assuming a PKI, pre-installed keys or an out-of-band-channel. Well established solutions exist, but they are not ideal for the type of self-contained networks targeted by LiFi communication. In this work we investigate how the physical properties of a LiFi channel can be used to replace these mechanisms, resulting in a more convenient and also more efficient solution for key exchange. To this end we propose a new type of secret-less key exchange (SEKA) that does not rely on any pre-shared secrets, and instead runs in two phases: a short bootstrap phase where we make stronger assumptions on the physical security, ruling out active attacks. This can be realized by putting all devices in a closed room, taking advantage of the light's confineability feature. The bootstrap phase is followed by a more classical key-exchange phase, where the actual key material gets exchanged in the presence of active attacks - relying on the shared states from the bootstrap phase. We formally define this new type of key-exchange protocol which offers authenticated key exchange with post-compromise security without relying on pre-shared secrets. We then show that a simpler and more efficient version of the signed Diffie-Hellmann protocol, now relying on MACs instead of signatures for the mutual authentication, can be proven secure in our model. Finally, a proof-of-concept implementation of the SEKA protocol is evaluated in a testbed demonstrating the efficiency gains of our approach.

We assess the impact of synchronization errors in distributed multiple-input multiple-output (D-MIMO) LiFi systems when using Ethernet as fronthaul. To this end, we perform a sensitivity analysis of a distributed multiple-input single-output (D-MISO) LiFi system model by running link level simulations of a joint transmission scheme in a worst-case scenario. Specifically, we investigate the impact of timing errors between distributed transmitters (TXs) on the frame synchronization rate and the block error rate (BLER) for the two IEEE Std 802.15.13 physical layers (PHYs), It is found that timing errors should not exceed the inverse system bandwidth in order to enable reliable communication. This allows a quantification of the synchronization accuracy requirements of distributed TXs in a D-MIMO realization of IEEE 802.15.13 networks using Ethernet as fronthaul. We also show that the required synchronization accuracy is achieved by using the IEEE 1588 Precision Time Protocol (PTP) together with synchronous Ethernet (SyncE).

In this paper, we evaluate the effectiveness of compressed-sensing-based channel estimation in LiFi orthogonal frequency-division multiplex (OFDM) systems with multiple-input multiple-output (MIMO). The sparseness of LiFi channels suggests that it is beneficial to utilize compressed sensing which has been investigated also for radio communications. In this paper, we formulate the mathematical problem of compressed-sensing for feedback generation in OFDM-based LiFi systems. We use well-known algorithms for both, sparse pilot design and sparse recovery and apply them to LiFi OFDM channels. We evaluate the effectiveness of these algorithms by measuring the achievable mean squared error (MSE) and vary the total numbers of subcarriers as well as the number of pilot subcarriers.

We presentHy-Fi, a system that aggregates light fidelity (LiFi) and radio frequency (RF)-based communication on the 802.11 (WiFi) physical layer by utilizing the MIMO capabilities in IEEE 802.11-compliant commodity WiFi chips.Hy-Fiis based on two key ideas. First, we use inexpensive commodity hardware to facilitate direct transmission of WiFi waveforms over the optical wireless channel, as this is proposed in the IEEE P802.11bb task group. Second, we use the MIMO signal processing from WiFi to aggregate LiFi and radio signals directly at the physical layer.Hy-Fiwas implemented as a prototype and evaluated in a small testbed. Experimental results reveal that our approach offers excellent robustness against signal fading, blockage and external interference in both, the optical and radio channels making it suitable for applications with very strict requirements to the packet delay and loss ratio. Moreover, the two channels, LiFi and RF, can be aggregated to double the link capacity in the best case. Finally, we demonstrate howHy-Ficould be used as wireless access technology in next-generation indoor enterprise networks providing both high capacity and seamless mobility.

In this paper, suitable estimation sequences and algorithms for the simultaneous channel estimation in an optical wireless communication system are assessed. We focus on a multi-user-MISO setup and an on-off-keying based pulsed-modulation physical layer. The performance of the tested configurations is evaluated using simulations under the constraints of imperfect time synchronization between the transmitters and band-pass distortions. Furthermore, a new family of binary channel estimation sequences, named Variable Sampling Factor (VSF) sequences, is proposed with the goal of enabling simultaneous estimation even between terminals using different sample clock rates. Despite a high variance of channel gains in the used model, the best presented algorithm is able to detect 6 out of 8 transmitters on average.

Multiple standardization activities have been started for optical wireless communications. In this paper, we summarize the ongoing work in the IEEE P802.15.13 task group. The goal is to make optical wireless communication usable for specialty applications, e.g., in industrial wireless networks. The current draft standard defines a medium access control (MAC) sublayer, supporting deterministic channel access for low latency/jitter through dynamic time division multiple access (TDMA), distributed multiple-input multiple-output (MIMO) operation for increased robustness, as well as two physical layers for high spectral efficiency and long reach, respectively. Currently, the specification is being finalized for publication. It is prepared for future updates to add support for the group of time-sensitive networking (TSN) standards. In this paper, we provide an overview over the upcoming standard.

The ongoing shop floor digitalization confronts manufacturers with challenges in computer networks. Wi-Fi became a standard for enabling mobile applications in factories but suffers from operating in the shared industrial, scientific and medical (ISM) radio band, which makes Wi-Fi networks prone to interference from wireless networks that operate in parallel. Consequently, Wi-Fi is a less reliable wireless network technology for smart factories. LiFi and 5G are alternatives that do not rely on ISM bands. With a combination of 5G and LiFi we reach flexibility, reliability, wide coverage, and high throughput for fixed and mobile devices in factories. In this paper, we demonstrate the use of LiFi as a non-3GPP access technology for the 5G core network and describe our initial testing of the N3IWF implementation. Besides, this paper describes a multistage demonstrator set-up, which allows to conduct initial validation tests in a distributed testbed environment. This approach enables the direct migration of developed system components into a real factory environment considering the rough environment of manufacturing halls.

We present Hy-Fi, a system which combines light fidelity (LiFi) and radio based on the WiFi physical layer waveform by using the MIMO features available in IEEE 802.11-compliant commodity chip sets. Hy-Fi is based on two key ideas. First, we use inexpensive COTS hardware to facilitate direct transmission of WiFi waveforms over the optical wireless channel, as this is proposed in the IEEE P802.11bb task group. Second, we use the MIMO signal processing to aggregate LiFi and radio signals at the physical layer. The system was implemented as a prototype and evaluated in a small testbed. Experimental results show that our approach offers robustness against signal blockage (Shadowing) and external interference in both, the optical and RF channels. Moreover, the two media (LiFi and WiFi) can be aggregated to double the capacity in the best case.