Modern society demands cheap, more efficient, and safer public transport. These enhancements, especially an increase in efficiency and safety, are accompanied by huge amounts of data traffic that need to be handled by wireless communication systems. Hence, wireless communications inside and outside trains are key technologies to achieve these efficiency and safety goals for railway operators in a cost-efficient manner. This paper briefly describes nowadays used wireless technologies in the railway domain and points out possible directions for future wireless systems. Channel measurements and models for wireless propagation are surveyed and their suitability in railway environments is investigated. Identified gaps are pointed out and solutions to fill those gaps for wireless communication links in railway environments are proposed.

Industry 4.0 and Industrial Internet refer to the expected revolution in production, utility management and, in general, fully automated, interconnected and digitally managed industrial ecosystems. One of the key enablers for Industry 4.0 lies on reliable and timely exchange of information and large scale deployment of wireless communications in industry facilities. Wireless will bring solutions to overcome the main drawbacks of the current wired systems: lack of mobility, deployment costs, cable damage dependency and scalability. However, the strict requirements in reliability and latency of use cases such as Factory Automation (FA) and Process Automation (PA) are still a major challenge and a barrier for massive deployment of currently available wireless standards. This paper proposes a PHY/MAC wireless communication solution for FA and PA based on Non-Orthogonal Multiple Access (NOMA) in combination with the 802.11n standard. The communication system proposed aims at delivering two different sets of services. The first service class is composed of Critical Services (CS) with strict restrictions in reliability and latency. The same communication system should convey also a second group of services, referred as Best Effort (BE) with more relaxed boundary conditions. The proposal theoretical background, a detailed transmission-reception architecture, the physical layer performance and the MAC level system reliability are presented in this paper. The solution provides significantly better reliability and higher flexibility than TDMA systems, jointly with a predictable control-cycle latency.

The Time-Sensitive networks paradigm envisions the integration of Operation Technology and Information Technology in the same network. One of the requirements for building Time-Sensitive networks is sharing a global time along the network. This requirement is especially critical in wireless systems, where there are few robust methods to perform accurate time transfer. In this paper, the problem of time transfer over realistic wireless channels is studied and a time distribution scheme is proposed. The time distribution scheme has three components: Precision Time Protocol, a novel timestamping method (enhanced timestamps) and an algorithm to implement the enhanced timestamps. The performance of the proposed scheme has been evaluated in MATLAB using the IEEE 802.11n standard under several standard Wireless Local Area Network channel models. The results show that the system can reach subnanosecond time transfer accuracy under Non-Line-of-Sight and time-variant conditions, but its performance greatly depends on the Signal-to-Noise-Ratio and on the channel variation rate.

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Industrial communications have very challenging requirements, especially in Factory Automation (FA) scenarios. Some of these requirements are: packet deadline bounds, high reliability, low transmission jitter, and communication determinism. Wireless communications solutions offer significant advantages over wired solutions: lower costs, faster and seamless deployment, higher flexibility and scalability, and free movement of the systems communicated wirelessly. However, standard wireless technologies do not provide enough performance to satisfy all of the industrial communications requirements in most cases and, therefore, wired solutions cannot be directly replaced by wireless solutions. In this work, we present SHARP (Synchronous and Hybrid Architecture for Real-time Performance in IWSAN), a novel hybrid architecture specially designed for industrial automation, where Ultra-Reliable Low-Latency Communications (URLLC) are required. This paper is mainly focused on the wireless segment of SHARP, a wireless architecture that includes a physical layer based on 802.11g along with a Time Division Multiple Access (TDMA) Medium Access Control (MAC) layer to ensure communication determinism, while maintaining backward compatibility with 802.11. Wireless SHARP segment behavior and its performance are evaluated through OMNeT++ simulations.

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Time Sensitive Networking (TSN) is becoming the standard Ethernet-based technology for converged networks of Industry 4.0 due to its capacity to support deterministic latency requirements. However, it cannot provide the required flexibility to support mobile industrial applications required for the factories of the future. This could be enabled through the integration of wireless technologies in factories, and in particular of 5G and Beyond networks since they have been designed to support ultrareliable and low-latency communications. This has triggered significant interest to integrate 5G and TSN networks, and first frameworks for such integration have been defined. However, the work is at early stages and the solutions to effectively integrate the two networks so that 5G can support TSN QoS levels are yet to be designed. This paper discusses current research and standardization work on 5G-TSN integration, and quantifies for a closed loop control application the 5GS bridge delay. The paper uses an example based on 5G-ACIA [1] to discuss open technical and research challenges to effectively integrate 5G and TSN.