Abstract
Industrial Internet-of-Things (IIoT) applications require reliable and efficient wireless communication. Assuming dense wireless sensor networks (WSNs) operating in a harsh environment, a concept of a time-division multiple access (TDMA)-based WSN enriched with electronically steerable parasitic array radiator (ESPAR) antennas is proposed and examined in this work. The utilized antenna provides one omnidirectional and 12 directional radiation patterns that can be electronically switched by the sensor node. We introduce a relay discovery algorithm, which selects those sensor nodes with an ESPAR antenna capable to act as relay. The selection of the relay nodes is based on a certain link quality threshold that algorithm uses as input. The outcome is a reduction in the number of layers or hops with a guaranteed Quality of Service (QoS). To emphasize the physical aspect of the wireless propagation, we introduce the measured antenna radiation patterns and consider two different path-loss propagation models representing blockage-free and blockage-prone industrial environments. A number of network simulations were performed and signal-to-noise ratio (SNR) as a link quality measure was examined with respect to the network density and different measured radiation pattern settings. The main outcomes show a tradeoff between SNR per link and the percentage of nodes that can serve as relays. As a result, we propose network design guidelines that take under consideration the QoS range with respect to SNR together with an optimal number of antenna radiation patterns that should be selected as a tradeoff between latency, energy consumption, and reliability in a network.
Highlights
T HE INDUSTRY 4.0 paradigm relies on ubiquitous connectivity between devices to maximize the information about automation processes in order to optimize them [1], [2]
We examined the problem of link quality impairment on typical industrial sites due to harsh propagation conditions and assess link quality improvements with switched-beam electronically steerable parasitic array radiator (ESPAR) antennas and a layered structure of the network introducing relaying nodes
In our time-division multiple access (TDMA) network comprised of sensor nodes and one WNP, we introduce a switched beam ESPAR antenna, which is a circular array, and by proper combination of the switches state can generate a directional radiation pattern that can be rotated from 0◦ to 360◦
Summary
T HE INDUSTRY 4.0 paradigm relies on ubiquitous connectivity between devices to maximize the information about automation processes in order to optimize them [1], [2]. The directional antennas that provide one fixed radiation pattern may not allow for an optimal operation in the case of dynamically changing environment conditions and nonstatic network topology For this reason, different concepts of reconfigurable antennas have been proposed [27], [28]. Applications of the switched-beam antenna concept for MAC layer algorithms improvement are known from the literature [29]–[32], but apart from presenting limited insight into the physical layer, those approaches rely on simplified ideal antenna radiation patterns and do not consider realistic parameters, such as beamwidth, sidelobe level, backward radiation, or angular switching resolution These aspects are critical for reliable assessment and appropriate design of both, the network topology and the future protocols. The discovered network structure can be used in combination with various routing algorithms as the one in [37]
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