Empirical Evaluation of NB-IoT and CAT-M Coverage for Underground Water System

Narrow-band Internet of Things (NB-IoT) and LTE CAT-M are part of low-power wide-area network (LPWAN) access technologies that provide long-range and energy-efficient network access to IoT devices. In this study, we conducted empirical measurements on NB-IoT and LTE CAT-M networks inside a street manhole. Street manholes are integral to smart city structures, where sensor implementation is essential. Our study demonstrates how to derive the network parameters from system information (SI) messages. More precisely, as we measured three commercial operators, we show the parameters and their influence on enhanced coverage level (ECL) repetitions. We consider signal strength and quality measurements at different locations inside the manhole. Our results indicate that when designing sensor networks for urban infrastructure monitoring, NB-IoT and LTE CAT-M should have different coverage margins in the implementation. Robust and low-cost NB-IoT construction leads to considering up to 2.4 dB higher coverage margins than LTE CAT-M. In this work, we analyze various relevant environmental conditions when evaluating and understanding underground signal propagation.