Introduction to LoRa
Many IoT devices are generally cost and power-restricted for the Internet of Things (IoT). There are many applications for which these devices only need a low data rate with a long range. Cellular technologies, Wi-Fi, or Bluetooth do not adequately serve these applications. This is where the role of LoRa (Long Range) technology comes into the picture. Low-power, long-range devices are known as LoRa. Earlier, cellular networks such as 2G and GPRS were utilized to deliver data from faraway places for Machine to Machine (M2M) communication. These networks consumed less power than 3G or LTE. However, network operators such as AT&T (US) declared the demise of 2G and GPRS at the start of 2017. LTE-M (LTE-MTC [Machine Type Communication]) and Narrowband-Internet of Things (NB-IoT) were the options provided by the 3GPP for M2M connectivity at that time. These, on the other hand, were not projected to be available until early to mid-2018. A protocol was needed that suits low-power, long-range, bi-directional communication devices. As a result, the LoRa network has become more widely deployed. Unlike cellular networks, LoRa does not require expensive spectrum licensing costs. They use an unlicensed frequency spectrum to send and receive data. M2M and IoT networks are the primary application areas of LoRa. This technology makes it possible for public or multi-tenant networks to connect many applications that are running on the same network. There are several LoRa installations available worldwide, both free and for a fee.
Semtech had patented and owned the core technologies associated with LoRa. The LoRa Alliance, which is a non-profit organization, was founded in early 2015 to meet a commercial need while also standardizing and promoting LoRaWAN, which is based on LoRa. This partnership is critical for ensuring interoperability across several national networks.
What is LoRaWAN and How Does it Work?
The LoRaWAN is a Low Power, Wide Area Networking protocol for wirelessly connecting battery-powered 'things' to the internet in regional, national, or global networks. It addresses key Internet of Things (IoT) requirements like bi-directional communication, end-to-end security, mobility, and localization services. A star-of-stars topology is used to implement LoRaWAN network architecture, with gateways relaying data between end devices and a central network server. The gateways connect to the network server via standard IP connections and function as a transparent bridge, transforming RF transmissions to IP packets and vice versa. The wireless communication takes advantage of the LoRa physical layer's Long-Range capabilities, allowing for a single-hop connection between the end device and one or more gateways. All modes may communicate in both directions, and multicast addressing groups can be used to make optimal use of the spectrum for operations like Firmware Over-The-Air (FOTA) updates or other mass distribution messages. LoRaWAN is becoming more popular in different application areas such as industries and smart cities because it is an inexpensive long-range, bi-directional communication protocol with very low power consumption such that the devices may function for ten years on a single battery. LoRaWAN utilizes the unlicensed ISM (Industrial, Scientific, and Medical) radio frequencies for network installations.
Architecture of LoRaWAN
Star-of-Stars topology is used to deploy the LoRaWAN networks. As shown in Fig. 1, the major components of the LoRaWAN network are end devices (or LPWAN sensors), gateway, network server, and application server.
1. End devices (or LPWAN sensors): A sensor, actuator, or both can be used as a LoRaWAN end device. They are usually battery-powered. The end devices communicate wirelessly with the LoRaWAN network via gateways that use LoRa RF modulation. Sensors or actuators deliver LoRa modulated wireless signals to gateways and/or receive wireless messages from gateways.
2. Gateways: The gateways are registered to a LoRaWAN network server through configuration settings. When a gateway gets a LoRa message from an end device, it simply sends it to the LoRaWAN network server. Gateways are linked to the Network Server through backhaul, which might be cellular (3G/4G/5G), Wi-Fi, Ethernet, fiber-optic, or 2.4 GHz radio connectivity.
3. Network Server: A network server is a piece of software that runs on a server that is responsible for securely processing application data. The network server manages the LoRaWAN network's gateways, end devices, applications, and users. A typical LoRaWAN network server has functionalities such as establishing secure 128-bit AES connections for message transit between end-devices and the application server (end-to-end security), validating end device authenticity and message integrity, uplink message deduplication, choosing the optimal gateway for downlink message routing, and routing uplink application payloads to the proper application servers.
4. Application Servers: The application server is responsible for processing application-specific data messages sent by end devices. It also generates all application-layer downlink payloads and distributes them to linked end devices through the network server. The obtained data may be analyzed using machine learning and artificial intelligence techniques. There can be more than one application server in a LoRaWAN network.
LoRaWAN Classes A, B, and C
LoRaWAN is divided into the following three classes that run concurrently.
1. Class A: Class A is a completely asynchronous system, sometimes known as an ALOHA system. This implies that the end nodes don't have to wait for a specific time to communicate with the gateway; instead, they just broadcast whenever they need to and remain inactive until then. If you have an eight-channel system that is completely synchronized, you could fill every time period with a message. As soon as one node completes its transmission, another begins. The theoretical maximum capacity of a pure aloha network, without any communication gaps, is around 18.4 percent of the maximum. This is mostly due to collisions since if one node is sending and another awakens and decides to transmit in the same frequency channel with the same radio settings, they will clash.
2. Class B: Messages may be transmitted down to battery-powered nodes using Class B. The gateway sends out a beacon every 128 seconds. Because all LoRaWAN base stations are slaves to a single pulse-per-second rate, they all emit beacon signals at the same time (1PPS). Within the 128-second cycle, all Class B nodes are allocated a time slot and notified when to listen. You can, for example, instruct a node to listen to every tenth-time slot, and when this occurs, a downlink message can be transmitted.
3. Class C: Class C nodes can listen indefinitely, and a downlink message can be transmitted at any moment. As it requires a lot of energy to keep a node fully awake and to operate the receiver at all times, this is mostly employed for AC-powered applications.
