In industrial environments, over several decades, Automated Guided Vehicles (AGVs) and Autonomous Mobile Robots (AMRs) have served to improve efficiencies of intralogistics and material handling tasks. However, for system integrators, the choice and effective deployment of improved, suitable and reliable communication and control technologies for these unmanned vehicles remains a very challenging task. Specifics of communication for AGVs and AMRs imposes stringent performance requirements on latency and reliability of communication links which many existing wireless technologies struggle to satisfy. In this paper, a review of latest AGVs and AMRs research results in the past decade is presented. The review encompasses results from different past and present research domains of AGVs. In addition, performance requirements of communication networks in terms of their latencies and reliabilities when they are deployed for AGVs and AMRs coordination, control and fleet management in smart manufacturing environments are discussed. Integration challenges and limitations of present state-of-the-art AGV and AMR technologies when those technologies are used for facilitating AGV-based smart manufacturing and factory of the future applications are also thoroughly discussed. The paper also present a thorough discussion of areas in need of further research regarding the application of 5G networks for AGVs and AMRs fleet management in smart manufacturing environments. In addition, novel integration ideas by which tactile Internet, 5G network slicing and virtual reality applications can be used to facilitate AGV and AMR based factory of the future (FoF) and smart manufacturing applications were motivated.INDEX TERMS Intelligent factory, factory of the future, 5G, smart manufacturing, industry 4.0, autonomous industrial equipment, AGV, AMR, tactile Internet, virtual reality, lean manufacturing.

Abstract-We propose a bidirectional radio-over-fiber link consisting of an optical downlink transmission employing the optical frequency multiplication principle, a remote local oscillator (LO) generation, a remote down-conversion of the radio-frequency uplink signals, and an optical uplink transmission employing intensity modulation-direct detection. Experiments demonstrate the optical up-conversion of 64-level quadrature amplitude modulated radio signals to 17.8 GHz after transmission over 4.4 km of multimode fiber, 12.5 and 25 km of single-mode fiber in the downlink; the uplink performance is evaluated in terms of down-conversion loss employing the optically generated LO.Index Terms-Broad-band wireless access, optical fiber communications, radio-over-fiber (RoF) systems.

We report on a record spectral efficient terahertz communication system using a coherent radio-over-fiber (CRoF) approach. High spectral efficient back-to-back and wireless THz transmission around 325 GHz is experimentally demonstrated using a 64-QAM-OFDM modulation format and a 10 GHz wide wireless channel resulting in a data rate of 59 Gbit/s.

Picocellular network designs at lower frequencies up to 6 GHz are compared to implementations at 60 GHz. System design aspects are discussed, including the implementation of MIMO. Very high bit rates of >10 Gb/s are achieved in mm-wave OFDM RoF systems. IntroductionThe ever increasing demand for high data rate transmission combined with the desire to connect end devices wirelessly led to intense research activities on new network architectures and technologies for in-building, small cell communication networks or picocellular networks. The goal is to connect up to hundreds of remote antenna units, which are simple in design, with a centralized head-end unit via fiber-optic transport systems, resulting in a flexible yet simple overall network design and therefore low-cost implementation. Radio-over-Fiber (RoF) is an attractive technology for these networks as it allows for centralization of signal processing and network management as well as radio signal generation. The radio signal then just needs to be transported to the remote antennas and radiated. Due to the high frequencies, optical fiber is widely considered as a transport medium due to its very low loss over long distances and over wide frequency ranges. Further, optical fiber is very light, flexible, bendable, and allows for consideration of wavelength-division multiplex (WDM) techniques. In this paper, two types of picocellular network architectures are discussed: lower-frequency networks for technologies like WiFi where the frequency range typically does not exceed 6 GHz. Fiber and remote antenna unit design issues will be reviewed. Further, the implementation of MIMO in such networks will be discussed and transmission results will be reviewed. A second part of the paper focuses on 60 GHz transmission systems, where the unique issues on signal modulation and upconversion and the potential of fiber chromatic dispersion to distort the signal lead to different considerations for network architecture design. Optical and electrical upconversion schemes will be compared and also aspects of single-carrier vs. multicarrier (OFDM) transport networks will be reviewed. Transmission results for >10 Gb/s in 60 GHz RoF designs are presented.

Radio-over-Fiber technologies enable efficient provisioning of broadband wireless services both in access and in in-building networks, in particular when combined with flexible optical routing and dispersion-robust RoF transport techniques, such as optical frequency multiplying.