The internet of things (IoT) has a significant economic and environmental impact owing to the billions or trillions of interconnected devices that use various types of sensors to communicate through the internet. It is well recognized that each sensor requires a small amount of energy to function; but, with billions of sensors, energy consumption can be significant. Therefore, it is crucial to focus on developing energy-efficient IoT technology and sustainable solutions. The contribution of this article is to support the implementation of eco-friendly IoT solutions by presenting a thorough examination of energy-efficient practices and strategies for IoT to assist in the advancement of sustainable and energy-efficient IoT technologies in the future. Four framework principles for achieving this are discussed, including (i) energy-efficient machine-to-machine (M2M) communications, (ii) energy-efficient and eco-sustainable wireless sensor networks (WSN), (iii) energy-efficient radio-frequency identification (RFID), and (iv) energy-efficient microcontroller units and integrated circuits (IC). This review aims to contribute to the next-generation implementation of eco-sustainable and energy-efficient IoT technologies.

Underground mine emergencies destroy communication infrastructure when situational awareness is most critical. Current systems rely on centralized network infrastructure, which fails during emergencies when miners are trapped and require rescue coordination. This paper proposes an energy-harvesting LoRa mesh network that addresses self-powered operation, interference management, and adaptive physical layer optimization under severe underground propagation conditions. A dual-antenna architecture separates RF energy harvesting (860 MHz) from LoRa communication (915 MHz), enabling continuous operation with supercapacitor storage. The core contribution is a decentralized scheduler that derives optimal timing offsets by modeling concurrent transmissions as a Poisson collision process, exploiting LoRa’s capture effect while maintaining network coherence. A SINR-aware physical layer adapts spreading factor, bandwidth, and coding rate with hysteresis, controls recomputing timing parameters after each change. Experimental validation in Missouri S&T’s operational mine demonstrates far-field wireless power transfer (WPT) reaching 35 m. Simulations across 2000 independent trials show a 2.2× throughput improvement over ALOHA (49% vs. 22% delivery ratio at 10 nodes/hop), 64% collision reduction, and 67% energy efficiency gains, demonstrating resilient emergency communications for underground environments.

A novel 1.8 GHz far field wireless power transfer (WPT) testbed was designed to achieve a long-distance energy harvesting in underground mines. Prior experimental studies indicate that underground mines suffer from severe radio frequency (RF) signal attenuation of 50 dB loss. Due to this severe signal attenuation characteristic, the currently deployed radio frequency energy harvesting (RF-EH) testbed cannot be deployed in underground mines. In this study, we designed and performed an empirical study with a military grade class A radio frequency wireless power transfer (RF-WPT) testbed experimenting with various digital modulation schemes. The various digital modulation schemes experimented included: BPSK, DBPSK, QPSK, OQPSK, Pi4DQPSK, 8PSK, D8PSK,16PSK, QAM16, QAM 64, QAM 256, QAM 1024, 2ASK, 2FSK, 4FSK, 8FSK, 16FSK, and OFDM. With the proposed testbed, we successfully performed long distance WPT in an underground mine at 20 meters by harvesting 4.2 volts DC with a Powercast P21XXCSR-EVB RF-EH receiver. We are specifically interested in understanding the optimal digital modulation scheme from the perspective of WPT efficiency in real world deployment scenario. Based on the outcome of this study, the optimal modulation scheme/s for WPT and wireless information transfer (WIT) in a simultaneous wireless information and power transfer (SWIPT) ecosystem is established. Amongst the various digital modulation schemes experimented with, 2ASK, 2FSK, 4FSK, 8FSK, 16 FSK and Pi4DQPSK exhibited high performance based on the maximum power transfer distance. Therefore, we recommend them as good candidates for WPT digital modulation schemes. The research also compared the impact of using Yagi and omnidirectional antennas. It was observed that there is a 5 meters performance loss between these antennas. Additionally, we mimicked a multipath wireless channel by introducing an N directional 15 dB coupler at the transmitter side, it was observed that underground mines lack multipath effect and hence, antenna diversity and MIMO technology will perform poorly in such environment.

Underground mines are susceptible to occasional roof falls and cave-ins, temporarily destroying the existing wireless communications and telemetry infrastr

Accurate path-loss models are essential for planning reliable wireless networks in underground mines, yet existing characterization studies rely on specialized channel sounders and vector network analyzers costing tens of thousands of dollars, placing them beyond the reach of most mine operators. This paper demonstrates that LoRa transceivers costing approximately US $15 per node can serve as a self-contained path-loss measurement instrument, logging the received signal strength indicator (RSSI) and signal-to-noise ratio (SNR) directly to a CSV file over a standard USB serial connection. A measurement campaign conducted at the Missouri S&T Experimental Mine on 31 March 2026 collected 4801 packets across four distinct underground canonical primitives: straight tunnel, T-junction, vertical shaft, and post-bend NLoS gallery at distances of 5 to 60 m using Waveshare Pico-LoRa-SX1262 boards operating at 915 MHz. The results reveal a pronounced two-zone propagation structure, including a line-of-sight (LoS) zone with a negative path-loss exponent of −0.34, confirming tunnel waveguide gain up to 25 m, followed by a steep NLoS zone with an exponent of 13.0 after a 24.0 dB bend diffraction loss. Environment-specific measurements quantify a 5.5 dB junction excess loss and a 29.5 dB shaft excess loss relative to a straight-tunnel reference. Spreading factor sensitivity tests across SF7, SF9, and SF12 confirm that RSSI measurements are consistent to within 2 dB across all SFs, validating the measurement methodology. The resulting four-zone path-loss model provides mine network planners with parameters sufficient for LoRa link budget design and relay node placement without any specialized RF instrumentation.

With the rise in smart devices communicating on internet, there is a huge demand in the delivery of internet bandwidth to fulfil subscribers’ aspirations. It is therefore important for internet network providers to understand the subscribers’ behavioural pattern in terms of internet bandwidth usage so as to meet up with the continuous rise in its demand. This research introduces the schematics of an android application effectively communicating with a remote database; Firebase cloud service. The classification of the subscribers’ internet traffic bandwidth consumption enables the android application to generate dataset of bandwidth utilization patterns of volunteered subscribers’ device which are grouped into 4 classes; A, B, C and D representing very high, high, medium and low data usage respectively. The collection of internet bandwidth usage of subscribers was recorded at intervals of every hour into the remote database in Firebase cloud.