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Ambient Backscatter Communication
Published in Parag Chatterjee, Robin Singh Bhadoria, Yadunath Pathak, 5G and Beyond, 2022
Tushar S. Muratkar, Ankit Bhurane, Ashwin Kothari, Robin Singh Bhadoria
Traditional BackCom is known for its low-power, low-cost and short-range communication. Increase in range is possible but at the cost of high power consumption. However, [63] designed a Lo-Ra BackCom system that can effectively communicate over a distance of 475 m. The Lo-Ra is based on chirp-spread spectrum (CSS) modulation, in which a ‘0’ bit is denoted as a continuous chirp that undergoes linear increase with, and a ‘1’ bit is a chirp that undergoes cyclical shifting in time.
Smart networks of autonomous in-situ soil sensors
Published in European Journal of Environmental and Civil Engineering, 2023
Xavier Chavanne, Jean-Pierre Frangi
LoRa modulation, a Chirp Spread Spectrum technique within a fixed bandwidth (125 kHz per channel usually), is mainly adjusted by a spreading factor (SF). SF fixes the amount of chirps LoRa uses to express a bit of data. In practice SF varies from SF7, or a high data transfer rate with index (theoretically 5.5 kb/s), to SF12, or a data rate index (theoretically 300 b/s). SF7 has the lowest time of emission -” time on air” - and consumption, but at the risk of important losses, whereas the reverse for SF12. Thus LoRa with SF trades between data transfer rate and transmission strength, which controls the number of lost points. Transmitter power is limited at 25 mW (or 14 dBm), at least in Europe. Coding Rate - CR - for error correction is fixed at it default value 4/5. The index is adjusted manually, or automatically owing to the activation of a LoRa function called Adaptative Data Rate (ADR). Through downlinks network servers adjust of the sensor transceiver in function of the strength of received signal.
LoRaWAN Networks for Smart Applications in Rural Settings
Published in IETE Technical Review, 2023
Luis M. Bartolín-Arnau, David Todoli-Ferrandis, Víctor Sempere-Payá, Javier Silvestre-Blanes, Salvador Santonja-Climent
LoRa modulation is based on CSS (Chirp Spread Spectrum), using linear frequency modulation chirp pulses with high bandwidth to encode information. Chirp pulses are sinusoidal signals with varying frequency over time, determining symbols that represent the information. The number of bits that can be encoded in each symbol is given by the spreading factor (SF), with a relation of 2SF. The range of SF values admitted is between 7 and 12 [17]. The duration (in seconds) of a symbol, knowing the SF and the bandwidth (BW) can be calculated as: Derived from (1), increasing the SF value means lowering the bit rate and therefore, increasing the Time on Air (ToA) of a packet. BW also influences this, inversely as the SF (incrementing BW reduces ToA), but due to limitations in there the regional parameters of the LoRaWAN network infrastructure used [18], this parameter is always set to 125kHz. This also reflects in the power consumption of the device, as it needs to enable the radio interface for longer periods to send the data. On the other hand, the coverage range increases for higher SFs values as this increased ToA results in greater robustness against noise [19]. LoRa modulation has another important characteristic that makes it fitting for the proposed application, and it is its immunity against the Doppler Effect. The small frequency shift caused by this effect, when transmitter and receiver move at different speeds (the GW is fixed, and the sensors will be moving), hardly affects the baseband signal in the time domain.
Using innovative smart water management technologies to monitor water provision to refugees
Published in Water International, 2020
Ryan W. Schweitzer, Ben Harvey, Murray Burt
In 2018 UNHCR conducted a desk review of available water level monitoring technologies. This review identified six different technologies that could be used for smart water management (SWM): electro-resistive, float-based resistivity, piezometric, ultrasonic, radar, and wave-radar probe. Eight water monitoring devices from six different companies (TankMatix, HummBox, Libelium, Tekelek, DecentLabs and KFA) were field tested. These devices used data communication technologies that included GSM cellular technology (3G and 4G) as well as low power wide area network, specifically Long Range Wide Area Network (LoRaWAN), which is based on chirp spread spectrum modulation (LoRa Alliance, 2015). Previous studies have showed the advantages of LoRaWAN over other ‘internet of things’ technologies (Mekki et al., 2017). Table 1 has a list of the devices that were tested in the pilot.