WOS3

Timing Synchronization for Smartphone-Based Optical Camera Communication
Frank von Schoettler (SEW-Eurodrive, Germany); Eike Lyczkowski (SEW-EURODRIVE, Germany); Zhidong Hua (Research & Development, Germany); Patrick Matalla (IPQ at Karlsruhe Institute of Technology, Germany); Sebastian Randel (Karlsruhe Institute of Technology, Germany)
The advent of industry 4.0 sets high and divers requirements for wireless communications. Visible light communication (VLC) is a technology that is able to address a set of those requirements. Within the area of VLC, we focus on optical camera communication (OCC) with a light emitting diode (LED) as sender and a complementary metal-oxidesemiconductor (CMOS) image sensor as receiver. The rolling shutter mechanism of the CMOS image sensor allows the system to achieve higher symbol rate than the frame rate. However, the sampling frequency of the rolling shutter is an unknown parameter that varies between smartphone models and therefore needs to be estimated if the system is required to work with a wide range of CMOS cameras. In this work, a non-data aided (NDA) digital timing synchronization algorithm employing a rolling shutter image sensor was analyzed using a spectral approach for application in an OCC system. The algorithm viability and wide applicability was demonstrated using the cameras of six different smartphone models.

Age-Of-Information Dependent Random Access in NOMA-Aided Multiple-Relay Slotted ALOHA
Gabriel G M Jesus (University of Oulu, Finland); João Luiz Rebelatto (Federal University of Technology – Parana, Brazil); Richard Demo Souza (Federal University of Santa Catarina, Brazil); Onel L. A. López (University of Oulu, Finland)
We propose and evaluate the performance of a NonOrthogonal Multiple Access (NOMA) dual-hop multiple relay (MR) network from an information freshness perspective using the Age of Information (AoI) metric. More specifically, we consider an age dependent (AD) policy, named as AD-NOMAMR, in which users only transmit, with a given probability, after they reach a certain age threshold. The packets sent by the users are potentially received by the relays, and then forwarded to a common sink in a NOMA fashion by randomly selecting one of the available power levels, and multiple packets are received if all selected levels are unique. We derive analytical expressions for the average AoI of AD-NOMA-MR. Through numerical and simulation results, we show that the proposed policy can improve the average AoI up to 76.6% when compared to a previously proposed AD Orthogonal Multiple Access MR policy.

Half-Duplex User Equipment Relaying Policies for Uplink Improvement in Beyond 5G Networks
Ioannis Avgouleas and Per Skillermark (Ericsson Research, Sweden); Gabor Fodor (Ericsson Research & Royal Institute of Technology (KTH), Sweden); Johan Söder (Ericsson, Sweden)
We consider a 5G cellular system, in which cellular user equipments (UEs) are willing to assist a cell-edge UE with a weak uplink (UL). We aim to improve the UL coverage as well as the end-to-end spectral and energy efficiency when the assisting UEs follow a group or multihop half-duplex relaying policy. Specifically, we study the UL performance under different distance-dependent fading conditions to understand when it is beneficial to use UE relaying. This question is motivated by recent advances in the Third Generation Partnership Project that suggests exploring the technology potential of physical layer groupcast and unicast over the sidelink for improving the UL coverage. Somewhat surprisingly, half-duplex UE relaying policies that exploit sidelink groupcast or unicast have not been thoroughly compared in the literature. System evaluations indicate that spectral efficiency can be improved over six times (compared to the case without relaying) with only two relaying UEs, while great energy efficiency gains are also achieved, provided that the time used for reception and transmission over the half-duplex relays is properly allocated. We also find that when relaying is beneficial, group and multihop relaying have their distinct advantages depending on the path loss exponent and the geometry of the system.

Real-Time MEMS-Assisted Beam Steering for Visible Light Communication System
Juan A Apolo (UPV Universitat Politècnica de València, Spain); Othman Isam Younus (Northumbria University, United Kingdom (Great Britain)); Beatriz Ortega (ITEAM Research Institute, Spain); Vicenc Almenar (Universidad Politecnica De Valencia, Spain); Zabih Ghassemlooy (Northumbria University, United Kingdom (Great Britain))
This paper presents a proof-of-concept of a luminaire-free visible light communications (VLC) link with real-time tracking based on a single micro-electro-mechanical systems (MEMS) mirror. The optical signal is applied to a polymer optical fiber (POF) and the collimated light is launched to the free space channel. The experimental setup includes a camera-based motion detection system and a MEMS mirror. The detection of the object is accomplished through the implementation of a background subtraction algorithm that utilizes Gaussian mixture models, followed by blob analysis and the application of geometrical transformations. Besides, the proposed system offers immunity against the receiver movement since it utilizes a single MEMS mirror to redirect the beam light and maintain a line-of-sight between the transmitter and receiver. The system is evaluated based on the bit error rate (BER) performance for different modulation bandwidths and detector gains. The results demonstrate the capability of the system to achieve speeds up to 10 Mbps using a non-return-tozero on-off keying (NRZ-OOK) modulation format.

Real Time Assessment of DML and EML with 25G-Class APD for Higher Speed PONs
Georges Gaillard (Orange & IMT Atlantique, France); Fabienne Saliou (Orange, France); Jeremy Potet (Orange Labs, Lannion & Institut Foton, Rennes 1 University, France); Philippe Chanclou (Orange Labs, France); Elena Durán-Valdeiglesias (Almae Technologies, France); Luiz Anet Neto (Imt-atlantique, France); Michel Morvan (Telecom Bretagne, France); Bruno Fracasso (Télécom Bretagne, France)
This paper aims at assessing two types of optical transmitters as potential candidates to realize transmissions at 50 Gbit/s in the context of Higher Speed Passive Optical Networks (HS-PON). A Receiver Optical Sub-Assembly (ROSA) with a high bandwidth (25 GHz) Avalanche Photodiode with a Transimpedance Amplifier (APD-TIA) is proposed to achieve high optical budget required for this application. Thus, we demonstrate, real time transmission for HS-PON at 25 and 50 Gbit/s, performed with a Directly Modulated Laser (DML) composed of a Distributed Feedback laser (DFB), or an External Modulation Laser (EML) composed of a DFB, integrated with an Electro-Absorption Modulator (EAM) and optionally aSemiconductor Optical Amplifier (SOA). The transmission is realized with reduced complexity of equalization (pre-emphasis 3-taps in emission+ Finite Impulse Response (FIR) filter 6-taps at the reception). A sensitivity of -29.4 dBm is obtained with a DML and 25 km of fiber at 25 Gbit/s and -22.7 dBm at 50 Gbit/s. The EML-SOA achieved a sensitivity of -27.8 and -24.4 dBm at 25 and 50 Gbit/s respectively. The results obtained open a perspective on the feasibility of HS-PON with DML at the emitter side, as a low-cost alternative to EML.