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Using advanced LPWAN technology in water supply networks to reduce water loss: Why? And what does this have to do with IoT?

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Abbildung 2: Aufbau eines LPWAN-Netzes (angelehnt an [9])

Years of experience and the realization that there are more ways to reduce water loss in a water supply through modern technology have led to this blog post. An LPWAN system is a new and promising technology that allows data to be collected and sent where conventional methods fail.

The term LPWAN stands for Low Power Wide Area Network. Low power refers to the characteristic of low power consumption. Wide Area Network is a well-known term for networks that are designed for long distances and are intended to cover a large area. A WAN can be built using two types of networks. These are both wired and wireless communications. Wireless communication is a basic feature of LPWAN, which supports various radio technologies. 

The deployment in the water supply network has so far been led either through the path of wired communication channels, or through cellular carriers and their wireless solutions. The trend towards wireless solutions has grown rapidly over the last 10 years, from our experience in automation technology, and has firmly embraced the IoT (Internet of Things). Many of these wireless solutions are dependent on cellular providers, high costs, and high energy consumption, even though only a small amount of data needs to be transmitted (e.g., meter reading and average of a flow in a meter well). According to the technical literature, these findings gave rise to the LPWAN.

Because even small amounts of data, such as a meter reading or level, can be collected by a variety of devices. LPWAN devices are often equipped with only one battery and can send their data to a receiver over several years and several kilometers away. Because of its long range and low power consumption, LPWAN can be considered suitable for many applications where other technologies prove inadequate. As a rule, this is always the case when it comes to the connection of simple sensor technology in places without easily available power supply - while at the same time large introduction distances to be bridged. 

In this blog post we would like to clarify the question why and under which external conditions LPWAN technologies can be used as well as the comparison to conventional data transmission technology. Furthermore, the general characteristics of an LPWAN will be explained and some advantages and disadvantages will be pointed out. The goal is to show the readers a modern technical solution that can be applied in an uncomplicated and almost maintenance-free way. 

 

How does digitization work in water supply

Digitization in water supply is, in the first step, the recording and processing of data of individual measured values necessary for monitoring a water supply network. Data is recorded via sensors on the respective structures of the waterworks and processed into digital form via controllers or programmable logic controllers (PLCs). This data is transmitted by means of communication components equipped with a telecommunication module. This data is accepted by a defined end point and is usually written to a database. The data is retrieved from the database by a process control system (PCS) or "Supervisory Control and Data Acquisition" (SCADA) system. The processed data is displayed to the end user in the DCS/SCADA in graphical, tabular and many other display options. From these displays, the end user can identify faults or anomalies, but also check or document the normal progress of his water supply network.

 

LPWAN features

Battery operation

An LPWAN module is powered by one or more batteries. At the same time, these should not be charged during operation. The lifetime of the LPWAN technology used device with one AA battery should be about 10 years. If the lifetime of the battery reaches its end, it will be replaced by a new one. In order to reach the defined 10 years, an energy-efficient operation with already power-saving sources is to be used. In doing so, these should not only extend the battery life, but also reduce costs as there will be fewer battery replacements. In order to shorten the operating time of the transmission modules, the duration for establishing communication as well as the communication transmission should be kept short. This requires a defined communication channel that wakes up the transmission module only for the transmission itself and transmits only needed data.

For use in a water supply all recorded or acquired sensor data must be transmitted. For data to be sent to actuators, the use of an LPWAN is not recommended and conventional transmission methods should be used instead, since actuators are usually dependent on other power sources.

 

Range

The size of a covered area is an important attribute in terms of cost. The number of modules used, as well as the communication participants, if only sensors are read, play an important role. The range should be selected in such a way that a failure of a module is prevented, the number of network participants remains manageable and the power used is portable in relation to the energy consumption.

The latencies and transmission speeds of the communication participants in a water supply are negligible, since water is rather inert in its movement. Thus, it does not matter in what time, how many participants, transmit their data. This has the advantage that a large range would not have a negative effect in the aforementioned deployment scenario.

 

Frequencies

LPWANs operate in different frequency ranges. Free frequencies in Europe are 433 MHz (unidirectional) and 868 MHz (bidirectional). However, frequency ranges are also used that lie outside the above-mentioned frequencies, such as 2.4 GHz or 5 GHz. A low frequency range increases a possible range of the radio network to be covered, respectively fewer modules are needed for coverage.

Furthermore, these low frequencies are more power-efficient, which can save costs. [4][5]­

 

Signal Strength

The signal strength is significant for the penetration of interfering elements. Interference elements are interference factors that can be located between communication partners. Their material properties thereby have different attenuations, which in turn form the interference factor:

Table 1: Attenuation of radio waves (adapted from [5])

 

Material

Damping

 

Examples general

Examples water supply

Wood

low

Furniture, ceilings, partitions

Pumping stations (wooden buildings)

gypsum

low

Partition walls without metal grid

Waterworks

Glass

low

Window pane

Windows to chambers in the elevated tank

Water

middle

Man, wet materials,

Aquarium

Measuring wells,Elevated tank in

Buildings

Wallstones

middle

Walls, ceilings

Basement, metering shafts,

Elevated tank,Deep wells, etc.

Concrete

high

massive Walls, steel reinforced

Concrete walls

Cellars, metering shafts, elevated tanks,

Deep well, etc.

Plaster

high

Partition walls with metal mesh

Cellars, waterworks, pumping stations

Metal

very high

Elevator shaft, fire doors, reinforced concrete

constructions

Elevated tanks in buildings with metal structure/

Metal jacket

The resulting negative effects in radio transmission can be noticeable as follows:

Table 2: Negative effects due to interference factors (adapted from [5])

 

Negative effect

Failure

Absorption

Signal is swallowed

Reflexion

Signal is reflected back

Refraction

Signal is redirected in another direction

Scattering

Signal duplication

 

 

Properties of a wireless network

It is recommended to use this wireless technology especially for IoT applications. In addition to its energy efficiency, it offers high building coverage and is designed for a large number of participants. The transmission data in a water supply network is usually very low. The low frequencies of LPWAN standards increase the ranges of individual LPWAN modules. Increasing the range simultaneously decreases the transmission speed. Low frequencies were chosen in LPWAN because it works against the weak points of already widespread systems, such as WLAN or mobile communications. Accordingly, the frequencies used in LPWAN technology are also separate from other technologies that are strongly represented in the consumer sector by WLAN or mobile communications (e.g. 2.4 GHz).  

                                                                      

 

Structure of an LPWAN network

The basic structure of an LPWAN network is represented by a star or mesh topology. To increase coverage, these two topologies are more often used together. In addition, the resulting range increases the number of subscribers in the covered areas. Individual base stations (audako Edge Gateways) can communicate with several sensor systems, also known as nodes. The nodes should be small in size. In addition, the costs for the sensor or actuator should be kept low. In particular, since base stations only receive data from nodes and send it to an end point, the number of transmission participants to the Internet is reduced, thus saving costs at the same time. The audako edge gateways thus provide the connection between the Internet and the nodes. In the scenario discussed here, this would be the audako cloud platform. This platform is where the data is stored, processed and made visually available to the user. If this is considered in summary, LPWANs try to distinguish themselves from WLAN and mobile communications by the following attributes:

 

 

- Low energy consumption

- Large coverage

- Small size of nodes

- Inexpensive sensors/actuators

- Network coverage in hard-to-reach localities

 

To meet the characteristics of an LPWAN, the network in the figure above has several requirements:

 

- Small amount of data, low overhead

- Low hardware requirement, easy implementation

- Suitability for mesh networks

- Secure transmission of data

- Devices should be addressable or reachable (e.g., for updates, reboots)

In order to work with small data packets in communication and thus to act in an energy-saving manner, the use of special protocols is necessary. In IoT networks, two protocols Message Queuing Telemetry Transport (MQTT) and Constrained Application Protocol (CoAP) have become established for this purpose.

 

 

CoAP - Constrained Application Protocol

As an IoT protocol, CoAP has emerged for devices that are resource-constrained. The connection is oriented to that of a Hypertext Transfer Protocol (HTTP) and Representational state transfer ful (RESTful) principle. To keep overhead low, it runs on the request/response principle, but also provides the publish/subscribe mechanism. CoAP uses the User Datagram Protocol (UPD) and protects its data using Datagram Transport Layer Security (DTLS). The basic idea is to keep the overhead small, thereby sending small packets and thus transmitting with fewer resources.

 

MQTT - Message Queuing Telemetry Transport

MQTT was developed for machine-to-machine (M2M) communications as well as the IoT. The MQTT protocol uses the Transmission Control Protocol (TCP) and can be protected via Transport Layer Security (TLS). MQTT employs the publish/subscribe mechanism, using a broker for communication management. The broker receives data from devices/nodes and forwards it to specific recipients. Only the broker (IP address) must be known for the data to be forwarded to the Internet. All other nodes are organized in a URL by the broker. The nodes defined in the broker are listened to and assigned on the basis of the URL list. However, actions can also be transferred to the nodes from the broker via a parameterization. The idea is to decouple the communication nodes, which can also communicate with each other below the broker via the broker. If a broker fails, the complete communication behind it also fails. The biggest advantage of this protocol, the decoupling, seems to be at the same time the biggest disadvantage.

 

 

Comparison of LPWAN with conventional transmission methods

The strengths of LPWAN are very advantageous for the purpose in a water supply network. Except for the nodes in a water supply network, such as an elevated tank or a deep well, the use of LPWAN can only be welcomed, because the nodes are usually always equipped with their own power supply. In addition, there are often actuators here that also need to be controlled remotely, which is why the aforementioned conventional transmission methods are more suitable for said nodes. However, if the metering shafts, intermediate tanks, pressure control shafts or water meters of house connections are considered, which do not have a separate or own power connection on site, the use of battery-powered transmission modules is only recommended. The characteristics described in advance indicate a pure advantage by using them in the scenario under consideration. 

 

 

The following sources were used for this post:

[1] DVGW: Digitalisierung in der Wasserversorgung:https://www.dvgw.de/themen/wasser/organisation-und-management/digitalisierung-in-der-wasserversorgung.

[2] ITWissen: Weitverkehrsnetz, 13.09.2020:https://www.itwissen.info/WAN-wide-area-network-Weitverkehrsnetz.html.

[3] TechTarget: LPWAN (Low-Power Wide Area Network), https://www.computerweekly.com/de/definition/LPWAN-Low-Power-Wide-Area-Network.

[4] B.S. Chaudhari und M. Zennaro: LPWAN Technologies for IoT and M2M Applications, Chennai Indien: Academic Press, 2020.

[5] Elektronik Kompendium: Funktechnik (Grundlagen),https://www.elektronik-kompendium.de/sites/kom/0810301.htm.

[6] Smartmakers: LoRaWAN-Reichweite, Teil 1: Die wichtigsten Faktoren für eine gute LoRaWAN-Funkreichweite, 10.03.2019:https://smartmakers.io/lorawan-reichweite-teil-1-die-wichtigsten-faktoren-fuer-eine-gute-lorawan-funkreichweite/.

[7] M. Liepert, m3 management consulting: LoRaWAN: Die drahtlose Kommunikation der Internet of Things?, 23.10.2018:https://www.m3maco.com/blog-item/lorawan-die-drahtlose-kommunikation-der-internet-of-things.

[8] R. Decker und A. Saß: Digitalisierung und Energiewirtschaft: Technologischer Wandel und wirtschaftliche Auswirkungen, Wiesbaden Deutschland: Springer Gabler, 2020.

[9] M. Linnemann, A. Sommer, and R. Leufkes: Deployment potentials of LoRaWAN in the energy industry: practical book on technology, application, and regulatory constraints, Wiesbaden Germany: Springer Vieweg, 2019.

[10] M. May: CAFM-Handbuch: Digitalisierung im Facility Management erfolgreich einsetzten, Wiesbaden Germany: Springer Vieweg, 2018, 4th edition.