1 Introduction
Pollutant | Short term limit | Long term limit |
---|---|---|
PM10 | 50 μg/m3 (1 day) | 40 μg/m3 (calendar year) Should not be exceeded on more than 35 days/year |
PM2.5 | 25 μg/m3 (calendar year) | |
O3 | 180 μg/m3 (1 hour) | |
120 μg/m3 (daily 8 hour mean) | ||
Should not be exceeded on more than 25 days per year averaged over 3 years | ||
NO2 | 200 μg/m3 (1 hour) | 40 μg/m3 (calendar year) |
Should not be exceeded on more than 18 hours/year | ||
SO2 | 350 μg/m3 (1 hour) | |
Should not be exceeded on more than 24 hours/year | ||
125 μg/m3 (1 day) | ||
CO | 10 mg/m3 (daily 8 hour mean) |
1.1 Current status of air pollution monitoring
1.2 What Wireless Sensor Networks (WSN) can provide
2 Low Power Wide Area Network (LPWAN) technologies
2.1 LoRa
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Class A: Uplink (from end node to the gateway/server) messages can be sent any time. Downlink windows are defined after uplink message.
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Class B: Extension of Class A with additional scheduled windows for downlink messages.
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Class C: End nodes listen always except when transmitting.
2.2 Sigfox
2.3 Narrow Band-Internet of Things (NB-IoT)
2.4 Comparison
Attributes/Technology | LoRa (SX1276)1 | Sigfox (S2-LPQRE)2 | NB-IoT (SARA-N2)2 |
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Frequency | Unlicensed ISM bands (433-, 868-, 915-MHz) | Unlicensed ISM bands (868 MHz, 902–920 MHz) | Licensed LTE frequency (700-, 800, -900 … MHz) |
Range | Up to several km, depending on parameters | Up to several km | Up to several km |
RX sensitivity | −148 dBm | −130 dBm | −135 dBm |
Data rate | 37.5 kbps | 600 bps | DL: 27.2 kbps/UL: 62.5 kbps |
Maximum payload | 255 bytes | 12 bytes | 1600 bytes |
Power consumption | TX: 29 mA (13 dBm) RX: 12 mA | TX: 20.6 mA (14 dBm) RX: 8.6 mA | TX: 100 mA (13 dBm) RX: 46 mA |
Price per transceiver (1000 pcs) | ∼3,66€ | ∼1,26€ | ∼10€ (for first available transceiver) |
Network Topology | Star topology, end devices do not have specific gateway | Star topology, end devices do not have specific gateway | Cellular network, end devices have specific gateway |
3 Experimental evaluations using LoRa
3.1 Measurement results
3.2 Comparison with Okumura–Hata path loss model
3.3 Potential utilization for air pollution monitoring
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Legislative and technological restrictions are limiting the minimum period at which the measured data can be provided.
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Depending on the sensor principle and the ambient conditions, a frequent remote sensor calibration could be necessary, which increases the required data rate.
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The data processing and evaluation can either be done at the node or at a central processing station, where the latter would significantly increase the transmissions per day.
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Additionally to the pollutant sensor data, date, timestamp and position could also be transmitted.
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If nodes are equipped with additional environmental sensors, such as temperature, humidity or other pollutants, the data rate is increasing.
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The link quality affects the number of transmission as lost or wrongly received packets might be resent.