Received September 18, 2021, accepted October 8, 2021, date of publication October 13, 2021, date of current version October 26, 2021.
Digital Object Identifier 10.1109/ACCESS.2021.3119757
Cluster-Based Communication Protocol and
Architecture for a Wastewater Purification
System Intended for Irrigation
JAIME LLORET 1 , (Senior Member, IEEE), LAURA GARCÍA 1,2 , JOSE M. JIMENEZ 1 ,
SANDRA SENDRA 1 , (Member, IEEE), AND PASCAL LORENZ 2 , (Senior Member, IEEE)
1 Instituto de Investigación para la Gestión Integrada de zonas Costeras, Universitat Politècnica de València, Gandia, 46730 Valencia, Spain
2 Network and Telecommunication Research Group, University of Haute Alsace, 68008 Colmar, France
Corresponding author: Jaime Lloret ()
This work has been funded by the European Union through the ERANETMED (Euromediterranean Cooperation through European
Research Area Net (ERANET) joint activities and beyond) project ERANETMED3-227 SMARTWATIR, by the ‘‘Ministerio de
Ciencia e Innovación’’ through the Project PID2020-114467RR-C33 and by ‘‘Ministerio de Agricultura, Pesca y Alimentación’’
through the ‘‘proyectos de innovación de interés general por grupos operativos de la Asociación Europea para la Innovación en
materia de productividad y sostenibilidad agrícolas (AEI-Agri)’’ project GO TECNOGAR. This work has also been partially funded
by the Universitat Politècnica de València through the post-doctoral PAID-10-20 program.
ABSTRACT The remote location of agricultural fields leads to the difficulty of deploying Precision
Agriculture (PA) systems as there is no Internet access in those areas. Therefore, the use of long-range
wireless technologies such as LoRa can provide connectivity to rural areas and allow monitoring PA systems
remotely. In this paper, a heterogeneous architecture and protocol that allows communication with both
WiFi and LoRa, including multiple hops in LoRa are presented. The design is based on a tree topology
comprised of electronic devices deployed on different areas of interest for PA systems such as the canals of
irrigation water, the fields, and the urban areas that generate wastewater. A set of practical tests with different
configurations have been performed to determine the correct operation of the proposed protocol. The results
show that the consumed bandwidth for both 433 MHz and 868 MHz frequency bands remained within the
limits for the most restrictive LoRa configurations. Therefore, different deployment needs can be addressed
with the implementation of this proposal. Furthermore, the use of packet transmission delays of 500 ms at
the CH node results in high successful packet delivery rates.
INDEX TERMS Algorithm, LoRa, precision agriculture, protocol, water quality.
I. INTRODUCTION the PA solutions cannot perform any actions in real-time
Precision agriculture (PA) systems aid in reducing water or quasi-real-time. Therefore, there is the need to provide
consumption and improving the quality and quantity of the connection to remote areas in order to deploy PA systems with
production. Most fields are located in rural areas with no all their functionalities.
Internet access resulting in difficulties in deploying PA solu- Long-rage technologies such as LoRa allows providing
tions. Ad-hoc networks allow forwarding the information to a connectivity to remote areas. The Things Network was
sink node by transmitting the data from one node to another. able to perform a LoRaWAN transmission that reached
However, deploying numerous sensing nodes is expensive 766 km utilizing a transmission power of 25mW in two
and may not serve the needs of the farmer. The use of drones occasions [3]. Although the maximum theoretical distance
to gather the data from sensors deployed on the fields can would not exceed 6 km for the configurations required to
be another solution for these remote fields [1]. However, achieve higher data rates in the 868 MHz frequency band [4].
this solution only allows to access the data at the time the Furthermore, the LoRaWAN protocol only considers a star
drone flies over the field. Another option is to use robots that topology, which presents a limit to the distance between node
move through the fields to collect the data from the sensor and gateway. Therefore, it may be necessary to add more hops
nodes [2]. However, with the use of vehicles as gateways, to the LoRa network. In this regard, studies on multi-hop
and mesh LoRa networks and protocols have been performed
The associate editor coordinating the review of this manuscript and by some researchers [5]. The scenario of LoRa nodes for
approving it for publication was Miguel López-Benítez . a water quality monitoring system intended for irrigation,
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
142374 VOLUME 9, 2021
,J. Lloret et al.: Cluster-Based Communication Protocol and Architecture for Wastewater Purification System
including an architecture with several hops, has been studied II. RELATED WORK
in previous works [6]. Where clusters of nodes are deployed In this section, we present previous works on protocols
on the water canals to monitor the state of the water and designed to be applied on WSN that are employed on agricul-
avoid false positives and false negatives by comparing the tural monitoring systems or to reduce of the consumed energy
data of all the nodes in the cluster. However, there can be for their functioning.
a scalability problem due to possible collisions among the Large-scale wireless networks benefit from technologies
messages forwarded by each node in a shared coverage area. such as LoRa for long-distance communication. However,
As it may be necessary to deploy several sensors on the fields, when distances larger than 2 km are necessary, there are new
combining LoRa with a smaller range wireless technology solutions not contemplated in the LoRaWAN protocol such
may be a good solution. as ad-hoc or mesh topologies. Therefore, new protocols have
There is a variety of short-range and medium-range wire- been designed to provide ad-hoc and mesh functionalities.
less technologies such as WiFi, ZigBee, or Bluetooth Low Huh and Kim presented in [8] a modification of the LoRa pro-
Energy (BLE). WiFi is the most accessible technology due to tocol for mesh networks. Furthermore, the proposed protocol
the wide variety of devices and prices which makes it a good utilizes time-division multiple-access to avoid collisions and
option for affordable solutions. Furthermore, its extensive the mesh network is limited to three hops. The protocol
documentation allows farmers and non-technicians to easily was tested on a fire pipe freeze monitoring system, a smart
operate the devices. Wi-Fi has been thoroughly studied for street light system, and a toxic gas monitoring system with
agricultural applications considering different types of vege- successful results. Lundell et al. proposed in [5] a routing
tation and different positions of emitter and receiver and, it is protocol intended for LoRa mesh networks. The protocol was
the most utilized wireless technology in PA IoT systems [4]. developed using the tunneling principle, where the packet is
ZigBee would also be a good solution but its usage in PA is forwarded if the node does not have Internet connection. Tests
yet to grow. Nodes such as the Heltec LoRa WiFi v2 [7] allow were performed utilizing Pycom LoPy 1.0 microcontrollers.
the utilization of both wireless technologies at the same time The results showed the feasibility of the proposed proto-
at an affordable price. The use of nodes with transceivers of col. A multi-hop LoRa network protocol based on concurrent
multiple technologies allows to provide more functionalities transmission was designed by Liao et al. [9]. In order to
to the system and to address the peculiarities of each scenario. avoid collisions, the authors utilized random timing offsets.
In this paper, a new communication protocol and archi- The results of the proof-of-concept experiments showed an
tecture for PA systems located in remote areas is presented. approximated 100% of packet delivery rate for topologies
This protocol has low overhead and is encapsulated over UDP with both high and low density. Furthermore, the frequency-
and LoRa. The architecture contemplates WiFi clusters that domain energy spreading effect led to a high possibility
obtain the data from the fields and the water channels and of packet collision survival including scenarios with small
transmits it over a multi-hop LoRa wireless network to the power offset.
gateway by utilizing a WiFi-LoRa bridge. The alerts caused The introduction of ad-hoc and mesh functionalities can
by water salinity, water pollution, malfunctioning elements of be applied to many scenarios. Gotthard and Jankech [10]
the nodes, low battery or down nodes are contemplated. Real utilized a supervised LoRa mesh network that utilized RSSI
tests on different locations have been executed to determine to determine the location of cars in a car park. The network
the performance of the protocol and determine the maximum was comprised of 1000 low-cost tags that reported the RSSI
distance that can be reached with the proposed architecture. to the central server. Furthermore, the authors proposed a slot
The novelty of our proposal is twofold: allocation scheme to avoid collisions. The results showed an
• Firstly, it contemplates multiple wireless communication error of 8 meters in car location and a lifetime of 5 years.
technologies, being LoRa and WiFi, and allows the devices In [11], Abrardo and Pozzebon presented a multi-hop LoRa
to communicate with each other to perform monitoring and network for underground medieval aqueduct monitoring in
anomaly detection activities. order to minimize the energy dissipation. This environment
• Secondly, the topology for LoRa communications is a required data monitoring every one hour or less transmission,
direct connection between the LoRa device and the gateway. low power consumption, and coverage of several kilometers.
In this proposal, multiple LoRa hops are introduced to reach Tests were performed utilizing Arduino nodes and Libelium
further distances. LoRa modules. The results showed a reduction of 50% in
This combination of multiple wireless technologies with power dissipation obtained from optimizing the wake-up
multiple LoRa hops to reach further distances has not been time. Lee and Ke designed in [12] a LoRa mesh network
explored in the existing works. to provide LoRa coverage to the campus area. Tests were
The rest of the paper is organized as follows. Section II performed utilizing Semtech SX1278 modules. The results
discusses the related work. The description of our pro- showed packet delivery ratios of 58.7% for the star topology
posal is depicted in Section III. The results are presented in and 88.49% for the proposed mesh topology with three hops.
Section IV. Section V compares the proposed system with Kulkarni et al. performed in [13] several experiments of LoRa
other previous published works. Finally, the conclusion and networks in a campus environment. The tests evaluated dif-
future work is presented in Section VI. ferent configurations of coding rates, bandwidth, spreading
VOLUME 9, 2021 142375
, J. Lloret et al.: Cluster-Based Communication Protocol and Architecture for Wastewater Purification System
factor to determine the transmission performance and link In this paper, a cluster-based multi-hop communication
quality. The results showed smaller transmission times with protocol for precision agriculture systems is presented.
high modulation coding schemes (MCS) and higher trans- Our work presents a new cluster-based algorithm and
mission times with the lower MCS settings. Lower MCS cre- communication protocol for the detection and purification
ates more collisions as well. Therefore, the authors conclude of waters that other authors have not previously defined.
that higher MCS settings should be utilized when possible. As opposed to other solutions, our work allows connectiv-
Lastly, Bertoldo et al. [14] presented a propagation study for ity with two wireless technologies and implements multiple
LoRa ad-hoc networks in urban environments. Tests were LoRa hops to reach longer distances.
performed utilizing the Adafruit Feather 32u4 LoRa board
with point-to-point and star topologies. For the point-to-point III. SYSTEM DESCRIPTION
topology, packet losses remained below 4%. However, for the In this section, we are going to describe the architecture, the
star topology, the packet losses ranged from 6% to 36%, with communication protocol, and the data analysis algorithm for
an average of 17%. a wastewater purification system intended for irrigation.
However, networks with high number of LoRa nodes trans-
mitting on the same channel at the same time are susceptible A. ARCHITECTURE
to collisions. In order to solve this problem, Branch and Cri- In this subsection, we detail the proposed architecture for our
centi [15] proposed a broadcast scheduling scheme for LoRa wastewater purification system for irrigation purposes.
relay networks. The proposal is intended for activities such The disposition of the area and the distribution of each type
as mine, tunnel, or pipe monitoring. It considers transmission of zone we have identified are presented in Fig. 1. As shown,
delays to determine when to transmit the message. Successful we identify several urban areas, a canal area, and fields.
tests were performed using Arduino boards and, Dragino and These areas communicate using wireless technologies. The
Modtronix LoRa shields, reaching distances of one kilometer wastewater disposed of by the population inhabiting the urban
per hop. Voigt et al. performed in [16] a study on the interfer- areas is transported to a purification station before being
ences caused between LoRa networks. The authors consider released to the irrigation canals. However, the quality of the
the use of multiple base stations and directional antennae. resulting water may not be optimal and non-treated waters
Simulations with the LoRaSim simulator were performed to and different contaminants may worsen the quality of the
test both solutions. The results showed that although both water before reaching its destined field. Thus, an in-situ water
proposals improve the performance of the scenarios with purification system is needed to ensure the quality and the
interferences, the best performance was obtained with mul- healthiness of the production. In Fig. 1, Urban Area 0 has an
tiple base stations. Ethernet/Fast-Ethernet connection to the data center. We have
Finally, these types of networks often face energy con- chosen wired communication because the performance of the
strictions. Therefore, several solutions have been considered data transmission is better, and the urbanized area allows
to optimize the energy consumed by the LoRa ad-hoc net- easy access of the infrastructure of the service provider. The
work. In [17], Heeger et al. analyze adaptive data rate (ADR) Canal area designates the zones where the irrigation canals
techniques for ad-hoc LoRa networks with energy constric- are located. Auxiliary canals connecting to the principal one
tions. ADR was extended with the use of frequency shift
keying (FSK) and they propose a process for error recov-
ery. Simulations were performed with the incremental search
algorithm, the binary search algorithm, and a greedy search
that utilized SNR and RSSI. The results showed that the
greedy search algorithm was the best solution although it
presents implementation challenges. The binary search was
good for a high data rate, but it had difficulties with high
Spreading Factor (SF) settings. Lastly, the incremental search
performed better than the binary search with high settings but
not for FSK configurations. Klimiashvili et al. [18] analyzed
the energy consumption and delay of LoRa and WiFi Ad
Hoc networks with the NS3 simulator. In this paper, authors
present a mathematical model for the delay and energy con-
sumption. The results showed that LoRa presented higher
delay due to the low throughput and the duty cycle. Further-
more, WiFi presented less energy consumption than LoRa for
distances below 300 meters when they are covered in one hop.
On the other hand, LoRa presented higher efficiency for large
distances. FIGURE 1. Deployment of node areas.
142376 VOLUME 9, 2021
Digital Object Identifier 10.1109/ACCESS.2021.3119757
Cluster-Based Communication Protocol and
Architecture for a Wastewater Purification
System Intended for Irrigation
JAIME LLORET 1 , (Senior Member, IEEE), LAURA GARCÍA 1,2 , JOSE M. JIMENEZ 1 ,
SANDRA SENDRA 1 , (Member, IEEE), AND PASCAL LORENZ 2 , (Senior Member, IEEE)
1 Instituto de Investigación para la Gestión Integrada de zonas Costeras, Universitat Politècnica de València, Gandia, 46730 Valencia, Spain
2 Network and Telecommunication Research Group, University of Haute Alsace, 68008 Colmar, France
Corresponding author: Jaime Lloret ()
This work has been funded by the European Union through the ERANETMED (Euromediterranean Cooperation through European
Research Area Net (ERANET) joint activities and beyond) project ERANETMED3-227 SMARTWATIR, by the ‘‘Ministerio de
Ciencia e Innovación’’ through the Project PID2020-114467RR-C33 and by ‘‘Ministerio de Agricultura, Pesca y Alimentación’’
through the ‘‘proyectos de innovación de interés general por grupos operativos de la Asociación Europea para la Innovación en
materia de productividad y sostenibilidad agrícolas (AEI-Agri)’’ project GO TECNOGAR. This work has also been partially funded
by the Universitat Politècnica de València through the post-doctoral PAID-10-20 program.
ABSTRACT The remote location of agricultural fields leads to the difficulty of deploying Precision
Agriculture (PA) systems as there is no Internet access in those areas. Therefore, the use of long-range
wireless technologies such as LoRa can provide connectivity to rural areas and allow monitoring PA systems
remotely. In this paper, a heterogeneous architecture and protocol that allows communication with both
WiFi and LoRa, including multiple hops in LoRa are presented. The design is based on a tree topology
comprised of electronic devices deployed on different areas of interest for PA systems such as the canals of
irrigation water, the fields, and the urban areas that generate wastewater. A set of practical tests with different
configurations have been performed to determine the correct operation of the proposed protocol. The results
show that the consumed bandwidth for both 433 MHz and 868 MHz frequency bands remained within the
limits for the most restrictive LoRa configurations. Therefore, different deployment needs can be addressed
with the implementation of this proposal. Furthermore, the use of packet transmission delays of 500 ms at
the CH node results in high successful packet delivery rates.
INDEX TERMS Algorithm, LoRa, precision agriculture, protocol, water quality.
I. INTRODUCTION the PA solutions cannot perform any actions in real-time
Precision agriculture (PA) systems aid in reducing water or quasi-real-time. Therefore, there is the need to provide
consumption and improving the quality and quantity of the connection to remote areas in order to deploy PA systems with
production. Most fields are located in rural areas with no all their functionalities.
Internet access resulting in difficulties in deploying PA solu- Long-rage technologies such as LoRa allows providing
tions. Ad-hoc networks allow forwarding the information to a connectivity to remote areas. The Things Network was
sink node by transmitting the data from one node to another. able to perform a LoRaWAN transmission that reached
However, deploying numerous sensing nodes is expensive 766 km utilizing a transmission power of 25mW in two
and may not serve the needs of the farmer. The use of drones occasions [3]. Although the maximum theoretical distance
to gather the data from sensors deployed on the fields can would not exceed 6 km for the configurations required to
be another solution for these remote fields [1]. However, achieve higher data rates in the 868 MHz frequency band [4].
this solution only allows to access the data at the time the Furthermore, the LoRaWAN protocol only considers a star
drone flies over the field. Another option is to use robots that topology, which presents a limit to the distance between node
move through the fields to collect the data from the sensor and gateway. Therefore, it may be necessary to add more hops
nodes [2]. However, with the use of vehicles as gateways, to the LoRa network. In this regard, studies on multi-hop
and mesh LoRa networks and protocols have been performed
The associate editor coordinating the review of this manuscript and by some researchers [5]. The scenario of LoRa nodes for
approving it for publication was Miguel López-Benítez . a water quality monitoring system intended for irrigation,
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
142374 VOLUME 9, 2021
,J. Lloret et al.: Cluster-Based Communication Protocol and Architecture for Wastewater Purification System
including an architecture with several hops, has been studied II. RELATED WORK
in previous works [6]. Where clusters of nodes are deployed In this section, we present previous works on protocols
on the water canals to monitor the state of the water and designed to be applied on WSN that are employed on agricul-
avoid false positives and false negatives by comparing the tural monitoring systems or to reduce of the consumed energy
data of all the nodes in the cluster. However, there can be for their functioning.
a scalability problem due to possible collisions among the Large-scale wireless networks benefit from technologies
messages forwarded by each node in a shared coverage area. such as LoRa for long-distance communication. However,
As it may be necessary to deploy several sensors on the fields, when distances larger than 2 km are necessary, there are new
combining LoRa with a smaller range wireless technology solutions not contemplated in the LoRaWAN protocol such
may be a good solution. as ad-hoc or mesh topologies. Therefore, new protocols have
There is a variety of short-range and medium-range wire- been designed to provide ad-hoc and mesh functionalities.
less technologies such as WiFi, ZigBee, or Bluetooth Low Huh and Kim presented in [8] a modification of the LoRa pro-
Energy (BLE). WiFi is the most accessible technology due to tocol for mesh networks. Furthermore, the proposed protocol
the wide variety of devices and prices which makes it a good utilizes time-division multiple-access to avoid collisions and
option for affordable solutions. Furthermore, its extensive the mesh network is limited to three hops. The protocol
documentation allows farmers and non-technicians to easily was tested on a fire pipe freeze monitoring system, a smart
operate the devices. Wi-Fi has been thoroughly studied for street light system, and a toxic gas monitoring system with
agricultural applications considering different types of vege- successful results. Lundell et al. proposed in [5] a routing
tation and different positions of emitter and receiver and, it is protocol intended for LoRa mesh networks. The protocol was
the most utilized wireless technology in PA IoT systems [4]. developed using the tunneling principle, where the packet is
ZigBee would also be a good solution but its usage in PA is forwarded if the node does not have Internet connection. Tests
yet to grow. Nodes such as the Heltec LoRa WiFi v2 [7] allow were performed utilizing Pycom LoPy 1.0 microcontrollers.
the utilization of both wireless technologies at the same time The results showed the feasibility of the proposed proto-
at an affordable price. The use of nodes with transceivers of col. A multi-hop LoRa network protocol based on concurrent
multiple technologies allows to provide more functionalities transmission was designed by Liao et al. [9]. In order to
to the system and to address the peculiarities of each scenario. avoid collisions, the authors utilized random timing offsets.
In this paper, a new communication protocol and archi- The results of the proof-of-concept experiments showed an
tecture for PA systems located in remote areas is presented. approximated 100% of packet delivery rate for topologies
This protocol has low overhead and is encapsulated over UDP with both high and low density. Furthermore, the frequency-
and LoRa. The architecture contemplates WiFi clusters that domain energy spreading effect led to a high possibility
obtain the data from the fields and the water channels and of packet collision survival including scenarios with small
transmits it over a multi-hop LoRa wireless network to the power offset.
gateway by utilizing a WiFi-LoRa bridge. The alerts caused The introduction of ad-hoc and mesh functionalities can
by water salinity, water pollution, malfunctioning elements of be applied to many scenarios. Gotthard and Jankech [10]
the nodes, low battery or down nodes are contemplated. Real utilized a supervised LoRa mesh network that utilized RSSI
tests on different locations have been executed to determine to determine the location of cars in a car park. The network
the performance of the protocol and determine the maximum was comprised of 1000 low-cost tags that reported the RSSI
distance that can be reached with the proposed architecture. to the central server. Furthermore, the authors proposed a slot
The novelty of our proposal is twofold: allocation scheme to avoid collisions. The results showed an
• Firstly, it contemplates multiple wireless communication error of 8 meters in car location and a lifetime of 5 years.
technologies, being LoRa and WiFi, and allows the devices In [11], Abrardo and Pozzebon presented a multi-hop LoRa
to communicate with each other to perform monitoring and network for underground medieval aqueduct monitoring in
anomaly detection activities. order to minimize the energy dissipation. This environment
• Secondly, the topology for LoRa communications is a required data monitoring every one hour or less transmission,
direct connection between the LoRa device and the gateway. low power consumption, and coverage of several kilometers.
In this proposal, multiple LoRa hops are introduced to reach Tests were performed utilizing Arduino nodes and Libelium
further distances. LoRa modules. The results showed a reduction of 50% in
This combination of multiple wireless technologies with power dissipation obtained from optimizing the wake-up
multiple LoRa hops to reach further distances has not been time. Lee and Ke designed in [12] a LoRa mesh network
explored in the existing works. to provide LoRa coverage to the campus area. Tests were
The rest of the paper is organized as follows. Section II performed utilizing Semtech SX1278 modules. The results
discusses the related work. The description of our pro- showed packet delivery ratios of 58.7% for the star topology
posal is depicted in Section III. The results are presented in and 88.49% for the proposed mesh topology with three hops.
Section IV. Section V compares the proposed system with Kulkarni et al. performed in [13] several experiments of LoRa
other previous published works. Finally, the conclusion and networks in a campus environment. The tests evaluated dif-
future work is presented in Section VI. ferent configurations of coding rates, bandwidth, spreading
VOLUME 9, 2021 142375
, J. Lloret et al.: Cluster-Based Communication Protocol and Architecture for Wastewater Purification System
factor to determine the transmission performance and link In this paper, a cluster-based multi-hop communication
quality. The results showed smaller transmission times with protocol for precision agriculture systems is presented.
high modulation coding schemes (MCS) and higher trans- Our work presents a new cluster-based algorithm and
mission times with the lower MCS settings. Lower MCS cre- communication protocol for the detection and purification
ates more collisions as well. Therefore, the authors conclude of waters that other authors have not previously defined.
that higher MCS settings should be utilized when possible. As opposed to other solutions, our work allows connectiv-
Lastly, Bertoldo et al. [14] presented a propagation study for ity with two wireless technologies and implements multiple
LoRa ad-hoc networks in urban environments. Tests were LoRa hops to reach longer distances.
performed utilizing the Adafruit Feather 32u4 LoRa board
with point-to-point and star topologies. For the point-to-point III. SYSTEM DESCRIPTION
topology, packet losses remained below 4%. However, for the In this section, we are going to describe the architecture, the
star topology, the packet losses ranged from 6% to 36%, with communication protocol, and the data analysis algorithm for
an average of 17%. a wastewater purification system intended for irrigation.
However, networks with high number of LoRa nodes trans-
mitting on the same channel at the same time are susceptible A. ARCHITECTURE
to collisions. In order to solve this problem, Branch and Cri- In this subsection, we detail the proposed architecture for our
centi [15] proposed a broadcast scheduling scheme for LoRa wastewater purification system for irrigation purposes.
relay networks. The proposal is intended for activities such The disposition of the area and the distribution of each type
as mine, tunnel, or pipe monitoring. It considers transmission of zone we have identified are presented in Fig. 1. As shown,
delays to determine when to transmit the message. Successful we identify several urban areas, a canal area, and fields.
tests were performed using Arduino boards and, Dragino and These areas communicate using wireless technologies. The
Modtronix LoRa shields, reaching distances of one kilometer wastewater disposed of by the population inhabiting the urban
per hop. Voigt et al. performed in [16] a study on the interfer- areas is transported to a purification station before being
ences caused between LoRa networks. The authors consider released to the irrigation canals. However, the quality of the
the use of multiple base stations and directional antennae. resulting water may not be optimal and non-treated waters
Simulations with the LoRaSim simulator were performed to and different contaminants may worsen the quality of the
test both solutions. The results showed that although both water before reaching its destined field. Thus, an in-situ water
proposals improve the performance of the scenarios with purification system is needed to ensure the quality and the
interferences, the best performance was obtained with mul- healthiness of the production. In Fig. 1, Urban Area 0 has an
tiple base stations. Ethernet/Fast-Ethernet connection to the data center. We have
Finally, these types of networks often face energy con- chosen wired communication because the performance of the
strictions. Therefore, several solutions have been considered data transmission is better, and the urbanized area allows
to optimize the energy consumed by the LoRa ad-hoc net- easy access of the infrastructure of the service provider. The
work. In [17], Heeger et al. analyze adaptive data rate (ADR) Canal area designates the zones where the irrigation canals
techniques for ad-hoc LoRa networks with energy constric- are located. Auxiliary canals connecting to the principal one
tions. ADR was extended with the use of frequency shift
keying (FSK) and they propose a process for error recov-
ery. Simulations were performed with the incremental search
algorithm, the binary search algorithm, and a greedy search
that utilized SNR and RSSI. The results showed that the
greedy search algorithm was the best solution although it
presents implementation challenges. The binary search was
good for a high data rate, but it had difficulties with high
Spreading Factor (SF) settings. Lastly, the incremental search
performed better than the binary search with high settings but
not for FSK configurations. Klimiashvili et al. [18] analyzed
the energy consumption and delay of LoRa and WiFi Ad
Hoc networks with the NS3 simulator. In this paper, authors
present a mathematical model for the delay and energy con-
sumption. The results showed that LoRa presented higher
delay due to the low throughput and the duty cycle. Further-
more, WiFi presented less energy consumption than LoRa for
distances below 300 meters when they are covered in one hop.
On the other hand, LoRa presented higher efficiency for large
distances. FIGURE 1. Deployment of node areas.
142376 VOLUME 9, 2021
