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18APPLICATION OF LORA WIRELESS TECHNOLOGY IN IOT NETWORKS
Jafarov N.,
cand.techn.sci.ass. prof. Azerbaijan Technical University
Azerbaijan Republic, Baku Nasiyev M.
Doctoral Degree, Faculty of Information and telecommunication technologies
Azerbaijan Technical University, Baku, Azerbaijan DOI: 10.5281/zenodo.7523831
ABSTRACT
In this article, we discuss main application areas of LoRa wireless technology. In our opinion, this technology has a number of features that make it very interesting for solving a certain range of problems. We will consider the history of the emergence of technology, how it is positioned, the typical architecture of LoRaWAN networks. Next, we turn to a detailed consideration of the physical features of its implementation.
Keywords: Long range; LoRa; IoT networks; microcontroller; internet of things; quality of service; sensor.
Introduction
LoRa is a wireless communication technology with high network capacity and low power consumption of end devices. According to IoT Analytics for the second half of 2020, it is the most common low-power wide area network (LPWAN) technology. LoRa technology is designed for machine-to-machine (M2M) communication and is a combination of a special LoRa modulation method and the LoRaWAN open communication protocol. This IoT communication technology is designed to serve up to 1
million devices on a single network, giving them up to 10 years of autonomy on a single AA battery [1,2].
LoRaWAN defines ten channels, eight of which have different data rates from 250bps to 5.5kbps, one LoRa channel with a high data rate of 11kbps, and one FSK channel with a rate of 50kbps. The maximum output power allowed by ETSI (European Telecommunications Standards Institute) in Europe is +14 dBm, except for the G3 band, which is allowed +27 dBm [1].
Table. 1.
LoRa specifications vary slightly depending on the region of application. And focused on reliable signal ___transmission and low power consumption-__
Europe North America China Korea Japan India
Frequency band 867869MHz 902-928MHz 470- 510MHz 920-925MHz 920-925MHz 865-867MHz
Channels 10 64 +8 +8
Channel BW Up 125/500kHz 125/500kHz
Channel BW Dn 125kHz 500kHz
TX Power Up (+14dBm) 20dBm typ (+30dBm allowed) In definition by In definition by In definition by In definition by
TX Power Dn (+14dBm) (+27dBm) Technical Committee Technical Committee Technical Committee Technical Committee
SF UP 7-12 7-10
Data rate 250bps-50kbps 980bps-21.9kpbs
Link Budget Up 155dB 154dB
Link Budget Dn 155dB 157dB
I. Network architecture
The LoRa technology is based on the modulation method of the same name, which was patented by Semtech. This method is based on the principle of spread spectrum and linear frequency modulation. In the process of transmission, data is encoded in broadband pulses with decreasing or increasing frequency over a certain time range. This solution makes it possible to make the receiver resistant to frequency deviations from the nominal value, which
reduces the requirements for the quality of the generator and allows the use of simple quartz resonators. Through the use of spread spectrum technology, the LoRa receiver can demodulate a signal that has a 20 dB noise level. The high sensitivity of the receivers (-148 dBm) makes it possible to use this technology over long distances, providing low power consumption and high communication stability [3].
LoRaWAN is an open communication protocol that defines the system architecture. This protocol
provides for a star topology. LoRaWAN was developed with the aim of organizing communication between low-cost devices that can operate on batteries (or other energy storage devices). To ensure an acceptable ratio of transmission rate to power consumption, the protocol provides for various classes of nodes. The LoRaWAN protocol defines a specific set of data rates, but the physical layer implementation of the OSI model will depend on the chosen chip.
In a LoRaWAN network, a node does not communicate with a specific gateway, but transmits data to several gateways. Each gateway forwards the received packet from the end node via transport (cellular network, Wi-Fi, Ethernet or other) to the cloud server. The server manages the network, drops redundant packets, performs security checks, plans the best route for the acknowledgment message, and controls the data rate. Using this architecture allows you to get rid of the handover procedure when moving mobile sensors within the network. The nodes in the network operate in an asynchronous mode and transmit data as they accumulate upon interruption. The Aloha method is used to access network resources. Refusal to constantly synchronize devices (as in mesh- or cellular networks) also saves battery power. In a network with
a "star" topology, it is difficult to organize a large network capacity at the same time as large coverage area [4]. To implement this possibility, LoRaWAN uses adaptive data rate and uses multi-channel multimodem transceivers in gateways so that messages can be transmitted simultaneously over several channels. Critical factors for throughput are the number of simultaneous channels, data rate (time on air), payload length, and how often nodes transmit. Since LoRa uses spread spectrum modulation, the signals are almost orthogonal to each other when different spreading factors are used. As the spreading factor changes, the effective data rate also changes. The gateway takes advantage of this property by being able to receive several different data rates on the same channel at the same time. If a node has a good connection and is close to the gateway, it can use a higher data rate, while its time on the air becomes shorter, which opens a "window" for transmission from other nodes [5]. The network can be built based on the required capacity, for example, you can increase the power in the network, install more gateways, but reduce the number of gateways that clients will listen to and increase the channel bandwidth by 6-8 times.
Fig. 1. Unlike a large number of existing networks that use a mesh architecture, where network nodes transmit information from one to another to expand coverage, LoRa network uses a star topology. This allows you to reduce the power consumption of devices (due to the lack of the need to forward packets from other devices),
and simplify the network architecture [2,3].
The problem of possible collisions during simultaneous data transmission by several points is solved by the central server of the LoRaWAN network, which sends control commands to the nodes (end-node) of the network through gateways. It also allocates time slots for transmission and reception individually for each end point (end-node). Addressing occurs by 32-bit address, unique for each node (end-node) [5]. The central server of the LoRaWAN network makes decisions on the need to change the data transfer rate by points (end-node), the transmitter power, the choice of the transmission channel, its start and duration, controls the battery charge of the end nodes (end-node). It can
fully control the entire network and manages each subscriber device individually.
Each LoRaWAN data packet sent by the end node (end-node) contains a unique application identifier belonging to the application on the service provider's server. This identifier is used by the central server of the LoRaWAN network for further routing of the packet and its processing application on the server (App Server) of the service provider [6]. In practice, as a rule, the services of provider are supplied by the manufacturer of end devices (end-node), which supports a service for processing data. In this service,
packets from the LoRaWAN network server are routed to work with this data to end users.
II. Device classes
The classes establish the necessary balance between downlink delays and battery life [6,7]. Below are most common types of classes used in Lora technology:
1. Bidirectional End Devices (Class A): Class A end devices allow bi-directional communication, in which the uplink transmission of each end device is punctuated by two short downlink receive windows. The transmission slot is scheduled by the end device based on its own communication needs, but may move slightly in time based on ALOHA access. Class A operations have the lowest power. Downstream transmission from the server is only possible after the next scheduled upstream broadcast.
2. Bidirectional Endpoints (Class B): In addition to the random down windows, there are additional time-scheduled receive windows. A device to communicate at the right time receives a special, time-synchronized, gateway beacon and listens to the air at the scheduled time.
3. Bidirectional end devices (class C): End devices listen to the air all the time, receive windows are closed only during transmission.
IoT requires strong security. To fulfill these requirements, two levels of security are used: the network level and the application level. Network security guarantees the identity of a node on the network, while the application security layer ensures that the network operator does not have access to end user application data [6].
I
h-l
t? OJ
i m
CMain powered actuators:
Devices which can afford to listen continuously No latency for downlink communication Downlink
B Battery Powered actuators:
Energy efficient with latency controlled downlink Slotted communication synchronized with a beacon
Battery powered sensors:
A Most energy efficient
Must be supported by all devices Downlink available only after sensor TX
Downlink Network Communication Latency
Fig. 3. End devices serving different applications may have different requirements. Device classes are used to
optimize application profiles.
III. Application areas of LoRa
The LoRa system can be well suited to the smart city ecosystem as the city is a clear geographical area. Although the choice of a specific implementation often depends on the topology, building density and the solvency of the population. The hallmark of smart city solutions is that end applications do not require constant broadband connectivity and high airtime. This level of need aligns well with the capabilities of LoRa. As part of a smart city, LoRa solutions can collect data on climate and air quality, for example, to decide whether roads need to be treated with chemicals. Another scenario could be monitoring the fullness of garbage cans. Soil moisture sensors can be used to timely start watering plants in parks. In addition to LoRa sensors, it can be used to activate street lighting, in the system of information messages about the time of arrival of vehicles. LoRa allows you to deploy those solutions that local authorities consider necessary, and due to the technological flexibility of LoRaWAN, the connection can be implemented anywhere where there is access to a data transmission network [4,7].
The development of the IoT device market has led to the fact that in addition to direct tracking of information about the position of an object, which was
implemented using cellular and satellite networks, it became possible to collect data on the state of the object (temperature, speed, data on specific objects in the cargo). A major breakthrough in the quality of such monitoring is the widespread use of LPWAN networks. Important thing in the process of asset tracing is the continuity of tracking, even when moving across borders. In this regard, the technology must be global and easily deployed in different locations and states. At the same time, the logistics industry does not require a large amount of transmitted data. Thus, the use of LoRa is a suitable solution because it allows you to deploy an energy-efficient trackers. In addition, due to the large capacity, LoRa can be effectively used in large warehouse complexes that process tens of thousands of shipments per day [7].
At the initial stage, smart buildings included disparate Internet of Things devices and implemented mainly energy saving solutions. With the development of IoT technologies, serious asset management has become possible. This includes monitoring of all life support systems, predictive maintenance of equipment, monitoring the state of the environment in the workplace. By 2020, many organizations are starting to realize that a smart building is not only a cost-saving
advantage, but even a means to attract and retain staff. Millennials, accustomed to automation everywhere, prefer those organizations that organize a convenient and attractive work environment in their choice of work, and in this regard, smart buildings become part of our lives. Applications that provide seamless workplace sharing, individual microclimate and ecology, and clean environment require more active implementation of the Internet of things. A study by IoT analytics company Berg Insight reports that at the end of 2018, the market for smart building solutions amounted to 151 million pieces of equipment. It is expected that the average annual growth (CAGR) until 2022 will be 33%. And the number of installed devices will reach 483 million. In 2018, the number of devices connected via cellular networks did not exceed 4.5 million and is projected to not exceed 19.4 million in 2022. The IoT Analytics company says that smart buildings are ranked 3rd (12%) after smart cities (23%) and industrial solutions (17%) in terms of the number of implemented IoT solutions in the world [8].
CONCLUSION
LoRa networks, by operating in an unlicensed band, can offer greater flexibility and lower cost of deployment and ownership compared to cellular networks. In this article, we tried to look under the hood of LoRa technology, namely, the type of modulation used in it and its main parameters, data encoding methods. In general, everything makes this technology unique and competitive.
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