Functional safety has become a crucial part of industrial automation. With industry environments being connected more than ever, achieving required functional safety depends on establishing safety-critical communication. Numerous application layer safety protocols have been developed to ensure compliance with functional safety standards for wired communications. However, with all the benefits wireless communications entails, wireless communication is pushing for an important place in the future of industrial automation. It is important that safety protocols also follow this transition and are able to operate as intended using a wireless channel. By default, openSAFETY frames are exchanged using UDP broadcast, whereas TCP provides additional reliability features. Thus, the aim of this paper is to analyze if safety-critical communication using a wireless channel can benefit from the additional reliability features provided by TCP. To answer this, we experimentally analyze the performance of openSAFETY protocol providing functional safety over the IEEE 802.11 standard for three different test cases. We analyze the performance in terms of median end-to-end delay and time spent by a safety node in a safe state for both protocol stacks. Results show that UDP provides lower median end-to-end delay, whereas TCP is able to achieve less time spent in a safe state under bounded delay constraint.

Interoperability is one of the important characteristics of the cyber-physical system (CPS) based automation system. Engineers connecting field devices and control applications in an automation system regularly encounter interoperability problems. ISO/IEC/IEEE 21451 is a series of standard, which provide the building blocks to enable interoperability among field devices and control applications. transducer electronic datasheets (TEDS) are provided as a standard transducer description format by ISO/IEC/IEEE 21450. This format provisions the syntactic interoperability among heterogeneous field devices. However, open platform communication unified architecture (OPCUA) is a key enabling technology to achieve semantic and network interoperability. Therefore, the aim of this paper is to provide an integration approach for ISO/IEC/IEEE 21450 TEDS and devices in the OPCUA semantic model. We propose an ISO/IEC/IEEE 21450 based device integration concept with service oriented architecture.

This article takes an analytical approach to investigate the temporal dynamics of interference in wireless networks. We propose a framework to calculate the autocorrelation of interference in Poisson networks and derive closed-form expressions for the case of Nakagami fading. The framework takes three correlation sources into account: the location of interferers, the wireless channel, and the data traffic. We introduce the interference coherence time-in analogy to the well-established channel coherence time-and show how its basic qualitative behavior depends on the source of correlation. The insights gained can be useful in the design of medium access control and retransmission protocols.

Our research investigates the concept of interference prediction as an unprecedented approach for interference management and medium access in wireless networks. This paper is a first step in this direction: it proposes and evaluates a simple interference prediction technique that is based on low-complexity learning. Nodes predict the interference situation they expect to experience in the near future and select the most favorable time slot to start the transmission of a multislot message. The performance gain is evaluated in a small-scale fading environment in terms of link outage and delay against random slot selection. Simulation results show that interference prediction is a promising building block for wireless systems. Additional studies are needed to explore advanced techniques and assess their feasibility.

This work explores the benefits in terms of energy efficiency that can be provided by device-to- device (D2D) communications in cellular systems. Analyzing a large cellular network using stochastic geometry, considering Nakagami fading and realistic system parameters, we explore the reduction that can be achieved in network power consumption, and the impact this reduction has on the performance of cellular users. When the network is not fully loaded, switching some cellular users into D2D mode results in a significant reduction of the network power consumption while the overall network throughput is maintained. Furthermore, it is observed that the impact of the reduction in the inter-cell interference arising from switching cellular users to D2D mode surpasses that from the new non- orthogonal transmissions. This translates into a slight improvement in the users' rates. Both analytical and simulation results are provided.

Device-to-device (D2D) communications is a promising candidate for increasing the throughput of cellular systems towards 5G. Its current consideration for inclusion in LTE-A is attracting a lot of research interest, including work on mode selection, bandwidth allocation, and power control. Some consider the uplink for D2D operation while others focus on operation over the downlink. It is still unclear, however, which link is preferable for D2D operation. This paper addresses this issue focusing on the outage performance of D2D receivers. We use stochastic geometry tools for our analysis, considering realistic system parameters and Nakagami fading. We find that the interference from the cellular system on the downlink, which is correlated over consecutive time slots, favors underlay D2D operation, resulting in a lower outage probability for the D2D transmissions.