Abstract
While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed as a wireless substitute for reliable process monitoring in industrial environments, most deployments use a single/static physical layer (PHY) configuration. Instead of limiting all links to the throughput and reliability of a single Modulation and Coding Scheme (MCS), you can dynamically re-configure the PHY of link endpoints according to the context. However, such modulation diversity causes links to coincide in time/frequency space, resulting in poor reliability if left unchecked. Nonetheless, to some level, intentional spatial overlap improves resource efficiency while partially preserving the benefits of modulation diversity. Hence, we measured the mutual interference robustness of certain Smart Utility Network (SUN) Orthogonal Frequency Division Multiplexing (OFDM) configurations, as a first step towards combining spatial re-use and modulation diversity. This paper discusses the packet reception performance of those PHY configurations in terms of Signal to Interference Ratio (SIR) and time-overlap percentage between interference and targeted parts of useful transmissions. In summary, we found SUN-OFDM O3 MCS1 and O4 MCS2 performed best. Consequently, one should consider them when developing TSCH scheduling mechanisms in the search for resource efficient ubiquitous connectivity through modulation diversity and spatial re-use.
Highlights
As the influx of technology into traditional industries advances the rise of Industry 4.0, this new industrial revolution requires process monitoring on an unprecedented scale
Signal to Interference Ratio (SIR) ≥ 0 dB; for O4 MCS2 useful transmissions under influence of O3 MCS1/MCS2 interference, PRRUTX ≥ 0.98 in 100% of cases where SIR ≥ 0 dB; for O4 MCS2 interfering with O3 MCS1/MCS2, PRRIF ≥ 0.57 in 68.8% of cases where SIR ≤ 0 dB; for O3 MCS1 interfering with O4 MCS2/MCS3, PRRIF ≥ 0.69 in 81.3% of cases where SIR ≤ 0 dB; for every UTX/interferer physical layer (PHY) combination, PRRUTX ≥ 0.97 in 96.1% of cases where SIR ≥ 6 dB
O3 MCS1 seems especially resilient to O4 MCS2 and MCS3 interference and the same is true for O4 MCS2 w.r.t
Summary
As the influx of technology into traditional industries advances the rise of Industry 4.0, this new industrial revolution requires process monitoring on an unprecedented scale. The industrial processes to monitor are often already in place and poorly suited for wired monitoring technologies due to limitations concerning cost, footprint, etc. Many are increasingly looking into wireless alternatives. Some industrial environments are so prohibitive, even state-of-the-art wireless networks can’t achieve ubiquitous connectivity. Isolated industrial sites with large metal constructions come to mind. In such challenging environments, it is common to observe highly localized changes in wireless link quality due to time-varying effects
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