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High‐speed discrete multitone serial data transmission over multi‐mode fibre at gross data rates up to 224 Gbit/s achieved with directly modulated oxide‐confined vertical cavity surface emitting lasers at 850 and 910 nm are presented.

Communication for the Internet of Things (IoT) currently is predominantly narrowband and cannot always guarantee low latency and high reliability. Future IoT applications such as flexible manufacturing, augmented reality and self-driving vehicles rely on sophisticated real-time processing in the cloud to which mobile IoT devices are connected. High-capacity links that meet the requirements of the upcoming 6G systems cannot easily be provided by the current radio-based communication infrastructure. Light communication, which is also denoted as LiFi, offers huge amounts of spectrum, extra security and low-latency transmission free of interference even in dense reuse settings. We present the current state-of-the-art of LiFi systems and introduce new features needed for future IoT applications. We discuss results from a distributed multiple-input multiple-output topology with a fronthaul using plastic optical fiber. We evaluate seamless mobility between the light access points and also handovers to 5G, besides low power transmission and integrated positioning. Future LiFi development, implementation and efforts towards standardization are addressed in the EU ELIoT project which is presented here.

In this paper, we report for the first time on a new channel modelling technique for multi-link LiFi scenarios. By considering simplified numerical calculation, it models the links between multiple optical frontends and multiple mobile devices much faster than previous approaches. For the first two diffuse reflections, we replace ray-tracing method by frequency domain channel modelling technique. For the other higher order diffuse reflections, we use a well-established model based on the integrating sphere. For validation of our new approach, we performed distributed 4x2 MIMO channel measurements. Comparison of simulation and measurement yields a relative mean square error below 5 percent for the signals with a free line-of-sight. Our new technique enables efficient modeling of mobile scenarios and analyzing statistical properties of the LiFi channels.

In this paper, results are presented from a long-term outdoor field trial using a rate-adaptive, LED-based optical wireless link over 100 m rooftop-to-rooftop distance. The optical link is installed in parallel to a 60 GHz link, enabling a direct comparison of both technologies for the same conditions by logging signal-to-noise ratios, data rates, and weather conditions. A model for the optical link has been developed for performance prediction based on weather data. Besides studying particular weather events, an analysis was conducted for the whole statistics. Results indicate that availability of the optical link was higher than 99.99%, despite severe weather conditions due to fog, rain, and snow. Although both links offer several hundred megabit per second, the optical link has a higher data rate 99.8% of the time while the 60 GHz link has a more consistent performance. Correlation is weak in bad weather conditions, e.g., if the SNR is low for the 60 GHz link due to heavy rain, the SNR in the optical link is high as the fog is light at the same time. Further measurements verify low latencies in the millisecond to sub-millisecond range for the optical link. Results indicate that the optical link is a promising low-cost solution for fixed access applications such as the replacement of fiber on the last 100 m to the end user, also denoted as wireless-to-the-home, and as a backhaul for Wi-Fi and small mobile radio cells.

International audience; We present a concept for networked optical wireless communications, also denoted as LiFi, to meet the requirements of industrial wireless applications. These are primarily mobility support with moderate data rates per device, reliable real-time communication, and integrated positioning. We describe a distributed multiuser multiple-input multiple-output architecture, serving mobile devices via an optical wireless infrastructure. The system consists of a central unit, being connected to a number of distributed optical frontends covering a larger area. Our main contribution is a medium access control protocol based on space division multiple access. Evaluation results demonstrate the advantages of joint transmission from adjacent optical frontends and the dynamic switching between spatial diversity and multiplexing. The relevance of spatial multiplexing becomes obvious through channel measurements in an indoor scenario. Moreover, we highlight a low-power physical layer based on on-off-keying for battery-powered mobile devices. Our architecture can easily integrate positioning by simultaneously measuring the time-of-flight between multiple optical frontends and the mobile device. We highlight the use of plastic optical fiber as an analog fronthaul technology and discuss the integration with other networks. The main functions described in this paper will be supported by the upcoming IEEE Std 802.15.13.

Networked optical wireless communication, also denoted as LiFi, is expected to play an important role in so-called smart hospitals. In this paper, we present the first experimental study of LiFi in an operating room at Motol University Hospital in Prague, Czech Republic. First, we perform one-to-one measurements using an optical transmitter (Tx) and receiver (Rx) and observe that channels with a free LOS provide sufficient signal strength for mobile communication inside the operating room. Then we combine the individual LOS links into a multiple-input multiple-output (MIMO) link using four distributed transmitters representing a wireless infrastructure, and six distributed receivers representing medical devices. In this configuration, at least two strong singular values of the MIMO channel matrix are observed which allow spatial multiplexing. By appropriately clustering the transmitters and selecting the users, mobile devices can be served in parallel. For data transmission, several multiplexing schemes such as time-division multiple access (TDMA) with one and two best links, TDMA with spatial reuse, space-division multiple access (SDMA) with two best links with and without zero forcing (ZF) are considered. Results show that SDMA with ZF increases the data rate by 2.7 times compared to baseline TDMA, resulting in a total data rate of 600 Mbit/s.

International audience; LiFi has been considered as a promising candidate for future wireless indoor networks. The IEEE P802.15.13 and P802.11bb standardization groups agreed upon channel models generated using the non-sequential ray tracing approach of OpticStudio. In this paper, in order to validate the channel modelling approach, at first 2 × 2 multiple-input multiple-output (MIMO) channel measurements are carried out over 200 MHz bandwidth using a channel sounder. The experimental scenario is also modeled in 3D by applying ray tracing. The obtained results indicate good agreement between simulations and measured channel impulse responses, from which parameters such as path loss and delay spread are derived. After validating the channel modeling approach, we investigate the singular values and the effect of user mobility onto the performance in a 4 × 4 distributed multiuser MIMO scenario.

Precise position information is considered as the main enabler for the implementation of smart manufacturing systems in Industry 4.0. In this article, a time-of-flight based indoor positioning system for LiFi is presented based on the ITU - T recommendation G.9991. Our objective is to realize positioning by reusing already existing functions of the LiFi communication protocol which has been adopted by several vendors. Our positioning algorithm is based on a coarse timing measurement using the frame synchronization preamble, similar to the ranging, and a fine timing measurement using the channel estimation preamble. This approach works in various environments and it requires neither knowledge about the beam characteristics of transmitters and receivers nor the use of fingerprinting. The new algorithm is validated through both, simulations and experiments. Results in an $\text{1}\;{\rm{m}} \times \text{1}\;{\rm{m}} \times \text{2}\;{\rm{m}}$ area indicate that G.9991-based positioning can reach an average distance error of a few centimeters in three dimension. Considering the common use of lighting in indoor environments and the availability of a mature optical wireless communication system using G.9991, the proposed LiFi positioning is a promising new feature that can be added to the existing protocols and enhance the capabilities of smart lighting systems further for the benefit of Industry 4.0.

Energy consumption is one of the critical issues in optical wireless communications transmitter design and a limiting factor to miniaturization and deployment in mobile devices. In order to reduce energy requirements, we assess a physical layer based on high-bandwidth on-off keying modulation. The use of on-off keying allows for highly efficient transmitter frontend designs that avoid operation of amplifier stages in a resistive mode, which has the potential of reducing their energy usage by an order of magnitude. Link-level simulations show that this physical layer can deal with typical frontend limitations and can operate in challenging non-line-of-sight channels. For these reasons, we believe that the solution evaluated here can deliver a significant contribution to optical wireless communications technology in a wide range of use cases.

In this paper, we investigate 2 x 2 MIMO light communication channels using non-sequential ray tracing simulations, and measurements over 200 MHz bandwidth using a MIMO channel sounder. Results indicate good agreement between simulations and measurements validating the accuracy of ray-tracing.

International audience; We propose a new system concept for LiFi in industrial wireless applications. A distributed multiuser multiple-input multiple-output (MU-MIMO) architecture is used, enabling seamless mobility, reliable low-latency communications, and integration with positioning and 5G.

International audience; We present LiFi channel measurements in a neurosurgery room of Motol University Hospital in Prague. Individual channels are combined into a virtual multiuser MIMO link. We report achievable data rates for different LiFi transmission schemes.

The concept of frequency interleaving (FI) for digital-to-analog converters (DACs) has recently experienced renewed interest, in order to overcome the DACs' bandwidth limitations. In this concept, the output signals of multiple DACs are interleaved in the frequency domain in order to generate a combined output signal that exceeds both the sampling rate and the bandwidth of a single DAC. In this paper, a mathematical framework for FI-DACs with a large number of DACs is presented and the inherent interdependencies between sampling rate, the number of samples, LO frequencies, symbol rate and analog frequency responses are highlighted. A mathematical expression for the distribution of data samples among the DACs is presented, taking into account bandwidth limitations of the analog components as well as guard bands to mitigate cross talk. In order to balance the FI-DAC's parameters a mathematical optimization approach is introduced and illustrated with examples. Both simulation and experimental results validate the FI-DAC concept, and an outlook on implementation issues completes this paper.

International audience; Previous researches on optical wireless communication (OWC) focused mainly on increasing the data rate for mobile broadband delivery. However, for new applications such as industrial wireless, reliability and robustness against interference play a crucial role. This paper focuses on the design , characterization, and real-world testing of novel solutions for OWC taking industrial requirements into account. Recent experimental works have demonstrated the feasibility of reliable OWC in a manufacturing environment. Here we propose to implement networked OWC which is also known as Li-Fi by means of a distributed MIMO approach enabling ultra-reliable low-latency communication (URLLC) which is an important use case for 5G and beyond mobile networks. For distributing the MIMO signals, plastic optic fiber (POF) is a promising low-cost solution offering high data rates, easy deployment and inherent robustness against electromagnetic interference. As POF may become a main component for Li-Fi using distributed MIMO, commercially available POF solutions are studied and their usability for this new application to distribute signal between central unit and multiple frontends is discussed.

As the use of optical wireless communication (OWC) in industrial production environments is gaining interest, it is necessary to consider the application's challenging requirements with respect to reliability and low latency. In this paper, we first analyze the factors limiting coverage and reliability in OWC. We discuss increased drive signal powers with an optional nonlinear post-equalizer, which improves the signal-to-noise ratio by an additional 3.5 dB. Further, spanning a multiple-input multiple-output (MIMO) channel and exploiting antenna diversity is shown to significantly increase the reliability of the OWC physical layer. The insights obtained from a series of experiments lead to a real-time demonstration of OWC with intrinsically high coverage and reliability. These first real-time results of OWC in an industrial production environment are discussed and physical layer data rates of up to 150 Mb/s with an average latency of $ 1 ms are shown.

CHARISMA aims to tackle low-latency and end-to-end security for converged fixed/wireless 5G networks in order to meet the complex demands of emerging business paradigms, such as Smart Cities, eHealth and Industry 4.0. In this paper, we present the key drivers and requirements towards a hierarchical, distributed-intelligence 5G architecture, supporting low latency, security and open access as features intrinsic to its design. We also investigate the business perspective of the proposed 5G solution and the changes that can be foreseen for the telecom ecosystem. Copyright © 2016 John Wiley & Sons, Ltd.

Smart phones, tablets, and the rise of the Internet of Things are driving an insatiable demand for wireless capacity. This demand requires networking and Internet infrastructures to evolve to meet the needs of current and future multimedia applications. Wireless HetNets will play an important role toward the goal of using a diverse spectrum to provide high quality-of-service, especially in indoor environments where most data are consumed. An additional tier in the wireless HetNets concept is envisioned using indoor gigabit small-cells to offer additional wireless capacity where it is needed the most. The use of light as a new mobile access medium is considered promising. In this article, we describe the general characteristics of WiFi and VLC (or LiFi) and demonstrate a practical framework for both technologies to coexist. We explore the existing research activity in this area and articulate current and future research challenges based on our experience in building a proof-of-concept prototype VLC HetNet.

We assess the performance of two distinct functional splits based on latency/latency variation and mapping efficiency, both individually and in unison. By considering hardware-offloading possibilities for a low-layer split (especially a pre-resource mapper split) using an option-6 software-based local thermal equilibrium split as an example, we show how data rate, Ethernet frame size and, in general, traffic generation characteristics will be very important aspects in the design of the future Ethernet mapping function. Then, an integrated Ethernet fronthaul with legacy and new/evolved split functionality operating at 100 Gb/s link rate is presented with the state-of-the art sub-100-ns latency variation for a timing-protocol flow. This is achieved through the application of a gap-filling aggregator, used for the first time in such a mobile fronthaul application.

Digital-to-analog converters (DACs) for high-speed optical communication systems based on CMOS technology have bandwidths lower than nowadays electro-optic components. A promising concept to circumvent this bottleneck is the frequency-interleaved DAC (FI-DAC) concept. In this paper, experimental results for the application of a 180 GS/s FI-DAC with 40 GHz analog bandwidth based on two DACs in a high-speed optical link are discussed and compared with simulation results. Thereby, phase and power mismatches, spectral overlap, clipping and the required DAC resolution are investigated. Signal-to-noise ratio (SNR) estimations based on a discrete multi-tone (DMT) signal show the influence of the individual analog components on the signal quality.

Current approaches to the fronthaul for centralized- or Cloud-Radio Access Networks (C-RANs) need to be revised to meet the requirements of next-generation mobile networks. There are two major challenges: first, fronthaul signals need to be transported over public fixed access networks, such as passive optical networks (PONs), typically sharing them with other services; second, higher data rates must be catered for due to larger radio bandwidths and greater use of multi-antenna techniques, such as massive MIMO. Using Ethernet as a new transport protocol for the fronthaul allows statistical multiplexing and enables convergence between fixed and mobile services. This new approach more easily benefits from common developments being made for service level agreements, functional virtualization and software-defined networking. Higher data rates will be supported by the move to new, and possibly flexible, functional split points inside the radio access network (RAN) protocol stack of the processing located in the central and distributed units, as is being investigated by a number of bodies. However, there are technical challenges with regard to latency and packet delay variation. This article summarizes the benefits of an Ethernet-based fronthaul for the next generation of mobile networks, its main challenges and how these may be overcome.

We discuss next-generation fronthaul solutions for 5G and legacy radio access networks. Architectures, findings and experimental results from recent lab and field trial activities are reported.

The use of Ethernet in the fronthaul permits convergence and exploitation of statistical multiplexing gains of the new interfaces, but minimum latency and latency variation requirements may become challenging. The techniques proposed to meet these challenges are summarized.

We describe low end-to-end latencies of 6.69 ms in the 5G CHARISMA network, that has been optimised for both device and system technologies speed, as well as with its virtualised, hierarchical and distributed, edge- centric architecture, that processes data as near as possible to their source and destination. Such an ultra-high speed 5G network can be utilised in intelligent transport system (ITS) applications, and we describe a public transport bus-based use case that takes advantage of the CHARISMA capabilities.

In this paper we investigate two promising approaches to reduce the optical bandwidth utilization in the mobile fronthaul of next-generation cloud radio access networks. We analyze and compare the performance of an analog radio-over-fiber and a new digital fronthaul in a chromatic dispersion-limited scenario. The former uses several analog channels, generated by up- and down-converting of baseband signals, and the latter utilizes simple OOK NRZ for the transmission to the remote radio head. Both principles are applied to a custom millimeter-wave system, consisting of several analog channels with baseband bandwidths as expected for 5G. The performance of both concepts at transmission rates of up to 100 Gb/s and 100 km of fiber is evaluated. We will show that both approaches are suitable for transmission distances typical for fronthaul and discuss their advantages and disadvantages. Furthermore, an optimized bandwidth concept for the analog radio-over-fiber system is presented, which enables transmission distances on the scale of metro networks.

Around the world, municipalities have been making substantial investments into broadband access infrastructure to accelerate the build-out of an urban phenomenon that has become known as a smart or connected city. At the 2016 Optical Fiber Communications Conference, a team contest, the Connected OFCity Challenge, was held to discuss the technological innovations and to examine dependencies and intricacies of a connected city project. The participants, four teams of experts coming from a cross-section of the industry, presented and defended their visions of future applications and innovative architecture and technologies to realize the interconnection. This paper provides a synthesis of the four competitive proposals offered for the contest and their ensuing discussions.

5G networks aim to tackle the complex demands of emerging business paradigms, such as Smart Cities, eHealth and Industry 4.0. In this paper, a hierarchical, distributed - intelligence 5G architecture is described, offering low latency, security, and open access as features intrinsic to its design. SDN and NFV principles are employed to create a networking solution applicable to a large number of high - specification 5G use case scenarios .

In this paper we derive information theoretic results for asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) in an intensity modulated direct detection (IM/DD) optical communication system subject to a range of constraints. ACO-OFDM is a form of OFDM designed for IM/DD systems. It is an effective solution to intersymbol interference (ISI) caused by a dispersive channel and also requires less optical power than conventional optical modulation formats. Although the classical Shannon capacity formula cannot be applied directly to an IM/DD system, we show that when ACO-OFDM is used in an IM/DD system, it can be adapted to calculate the information rate of the data-carrying odd frequency subcarriers. As a result conventional water filling techniques can be used for a frequency selective channel. These results are applied to indoor wireless systems using realistic parameters for the transmitter, receiver and channel. The maximum rate at which data can be transmitted depends on the channel, the electrical bandwidth and the transmitted optical power. Even when there is no line of sight (LOS) path, when the electrical bandwidth is limited to 50 MHz and the average optical power is limited to 0.4 W, data rates of approximately 80 Mbit/s can theoretically be achieved.

Coordinated multipoint or cooperative MIMO is one of the promising concepts to improve cell edge user data rate and spectral efficiency beyond what is possible with MIMOOFDM in the first versions of LTE or WiMAX. Interference can be exploited or mitigated by cooperation between sectors or different sites. Significant gains can be shown for both the uplink and downlink. A range of technical challenges were identified and partially addressed, such as backhaul traffic, synchronization and feedback design. This article also shows the principal feasibility of COMP in two field testbeds with multiple sites and different backhaul solutions between the sites. These activities have been carried out by a powerful consortium consisting of universities, chip manufacturers, equipment vendors, and network operators.

It is proposed that using Ethernet in the fronthaul, between base station baseband unit (BBU) pools and remote radio heads (RRHs), can bring a number of advantages, from use of lower-cost equipment, shared use of infrastructure with fixed access networks, to obtaining statistical multiplexing and optimised performance through probe-based monitoring and software-defined networking. However, a number of challenges exist: ultra-high-bit-rate requirements from the transport of increased bandwidth radio streams for multiple antennas in future mobile networks, and low latency and jitter to meet delay requirements and the demands of joint processing. A new fronthaul functional division is proposed which can alleviate the most demanding bit-rate requirements by transport of baseband signals instead of sampled radio waveforms, and enable statistical multiplexing gains. Delay and synchronisation issues remain to be solved.

Base station cooperation is envisioned as a key technology for future cellular networks, as it has the potential to eliminate intercell interference and to enhance spectral efficiency. To date, there is still lack of understanding of how imperfect carrier and sampling frequency synchronization between transmitters and receivers limit the potential gains and what the actual system requirements are. In this paper, OFDM signal model is established for multiuser multicellular networks, describing the joint effect of multiple carrier and sampling frequency offsets. It is shown that the impact of sampling offsets is much smaller than the impact of carrier frequency offsets. The model is extended to the downlink of base-coordinated networks and closed-form expressions are derived for the mean power of users’ self-signal, interuser, and intercarrier interference, whereas it is shown that interuser interference is the main source of degradation. The SIR is inverse to the base stations’ carrier frequency variance and to the square of time since the last precoder update, whereas it grows with the number of base stations and drops with the number of users. Through user selection, the derived SIR upper bound can be approached. Finally, system design recommendations for meeting synchronization requirements are provided.

Over-the-air transmission experiments with a realtime MIMO test-bed are reported. We describe in principle a hardware architecture for spatial multiplexing at high data rates, discuss in detail the implementation on a hybrid FPGA/DSP platform and show measured bit error rates from indoor transmission experiments. Per-antenna rate control and joint transmission are enabled as well using an ideal feed-back link. A functional test of these new techniques is described while detailed transmission experiments are still ongoing.

New software-defined open network concepts are proposed in this paper to enable an efficient implementation of front- and backhaul solutions for future 5G mobile networks. Main requirements for 5G front- and backhaul are derived and then related to the open network architecture enabling multiple operators to share the same physical infrastructure. The value of software-defined networking (SDN) is particularly outlined therefore. For the use of SDN in the fronthaul, CPRI over Ethernet (CoE) is proposed as a new transport protocol. In the backhaul, distributed security can be implemented using SDN where direct links are confined inside the access domain, as opposed to the current centralized security solution including also the transport domain. In this way, low latency can be realized e.g. for machine-type communications. As the benefits for fixed-mobile convergence are evident, SDN should be enabled increasingly in the access domain.

Coordination of base stations is a promising technique for reducing inter-cell interference in next-generation cellular systems. For the downlink of such systems, the authors study the degradation of zero-forcing precoded transmissions caused by imperfect channel estimation and channel variation over time. They derive exact expressions for the mean power of the desired signal received by an arbitrary user and of the interference caused by the mismatched precoder. By using these expressions, they show that for attaining a given signal-to-interference power ratio (SIR) these systems are limited by a maximum feedback delay of updated channel state information. Finally, they present a procedure to calculate the maximum tolerable feedback delay and to determine the separation between the non-precoded pilot symbols for guaranteeing a desired SIR.

For a downlink scenario with two base stations and one receiving mobile, where the base stations are connected by a noiseless finite-capacity backbone, we determine the optimal cooperation and coding strategy. The performance is not influenced by the degree of channel state information at the mobile, but it increases with increasing channel state information at the base stations. If the link capacities exceed finite thresholds, the system achieves full-cooperation performance. The optimal cooperation protocol is a simple one-shot strategy.

Base station cooperation is considered as a promising approach to increase the quality of service (QoS) in uplink. Base stations are connected via high-capacity backhaul links, which makes it possible to perform joint detection through information sharing among several base stations. Joint detection broadens the feasible signal to interference ratio (SIR) region, in which any SIR assignment for all users can be concurrently supported. Thus it provides a higher system throughput. We characterized the Pareto-optimal boundary of the feasible SIR region of power control with base station cooperation by utilizing the property of concave interference function. We suggest a distributed power control algorithm that exploits the broader feasible SIR region and optimizes the SIR assignment. Depending on the feasibility of the network to support cooperation, we analyze 3 degrees of cooperation: no cooperation, limited cooperation, and full cooperation.

We evaluate the interference limited spectral efficiency of a small cellular network using measurements with 3 sites at an ISD of 750 m. Each 3-sector site is equipped with cross-polarized panel antennas. We provide an efficient method to estimate the MIMO capacity from the measured data. We then compare the capacities of SISO and 2x2 MIMO with and without interference. At a fixed SNR of 10 dB, our cross-polarized interference free 2x2 setup achieves 5.7 bps/Hz which compares well to findings from Manhattan. For the best serving BS, the median 2x2 capacity including the received power and a reuse factor of 9 is 1.7 bps/Hz. This value increases to 3 bps/Hz when using frequency reuse 3 and 4.7 bps/Hz with full reuse.

A recently realized concept of a reconfigurable hardware test-bed suitable for real-time mobile communication with multiple antennas is presented in this paper. We discuss the reasons and prerequisites for real-time capable MIMO transmission systems which may allow channel adaptive transmission to increase link stability and data throughput. We describe a concept of an efficient implementation of MIMO signal processing using FPGAs and DSPs. We focus on some basic linear and nonlinear MIMO detection and precoding algorithms and their optimization for a DSP target, and a few principal steps for computational performance enhancement are outlined. An experimental verification of several real-time MIMO transmission schemes at high data rates in a typical office scenario is presented and results on the achieved BER and throughput performance are given. The different transmission schemes used either channel state information at both sides of the link or at one side only (transmitter or receiver). Spectral efficiencies of more than 20 bits/s/Hz and a throughput of more than 150 Mbps were shown with a single-carrier transmission. The experimental results clearly show the feasibility of real-time high data rate MIMO techniques with state-of-the-art hardware and that more sophisticated baseband signal processing will be an essential part of future communication systems. A discussion on implementation challenges towards future wireless communication systems supporting higher data rates (1 Gbps and beyond) or high mobility concludes the paper.

In OFDM-based space division multiple access (SDMA) systems, multiple users are served by a multiantenna base station simultaneously on the same frequency resources. In the uplink, each user's signal may be distorted by an independent carrier frequency offset (CFO), which impairs the orthogonality of the subcarrier signals and, if not properly compensated, results in performance degradations. We analyze the influence of multiusers' CFOs on the signal transmission in the OFDM-SDMA uplink and derive suitable bounds for the achievable signal-to-interference conditions. By modifying the signal model suitably, we develop a simple scheme for partial compensation of the CFO distortions. It allows to maintain the subcarrier-wise channel equalization and thus is well suited to be applied for a real-time system implementation. However, as CFOs impair the cyclic structure of the OFDM symbols, our scheme is not able to compensate for the entire distortion. The remaining interference is treated as additional noise, which limits the supported size of the CFOs.

Using Ethernet in the fronthaul can deliver the statistical multiplexing gains offered by the new functional splits proposed for the radio access network, but latency and delay variations are challenges that must be overcome.

We demonstrate an LED-based optical wireless link for fixed wireless access applications, at data rates of 1.5 Gbit/s over 50 m. Transmission between indoor equipment and outdoor access point is possible through metal-coated insulation glass., Comment: 3 pages, 2 figures, Optical Fiber Communication Conference 2021

International audience; The transfer of health monitoring data from multiple patients using wireless body-area networks requires the use of robust, and energy and bandwidth efficient multipleaccess schemes. This paper considers the frequency-division multiple access for the wireless uplink to a fixed access point when using infrared signals to collect medical data from several patients inside an emergency waiting room. The conventional optical orthogonal scheme applies Hermitian symmetry to obtain real-valued signals, which implies increased computational complexity. We consider a new approach transmitting only the real part of a complex-valued signal, where no such constraint is imposed. Based on the proposed scheme, and taking into account the limited dynamic range of an infrared light-emitting diode, we study the performance of direct current biased and asymmetrically clipped schemes, and show their advantage in terms of energy efficiency and computational complexity, as compared with the conventional schemes. For instance, we show that by using asymmetric clipping, around 35 mW less transmit power is needed to achieve a bit error rate of 10 −3 in the considered scenario. We also demonstrate the robustness of the proposed scheme against multiple access interference.