LoRaWAN

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LoRa (from "long range") is a physical proprietary radio communication technique. It is based on spread spectrum modulation techniques derived from chirp spread spectrum (CSS) technology. It was developed by Cycleo, a company of Grenoble, France.

LoRaWAN (Wide Area Network) defines the communication protocol and system architecture. LoRaWAN is an official standard of the International Telecommunication Union (ITU), ITU-T Y.4480.

Together, LoRa and LoRaWAN define a Low Power, Wide Area (LPWA) networking protocol designed to wirelessly connect battery operated devices to the internet in regional, national or global networks, and targets key Internet of things (IoT) requirements such as bi-directional communication, end-to-end security, mobility and localization services. The low power, low bit rate, and IoT use distinguish this type of network from a wireless WAN that is designed to connect users or businesses, and carry more data, using more power. The LoRaWAN data rate ranges from 0.3 kbit/s to 50 kbit/s per channel.

Features

LoRa uses license-free sub-gigahertz radio frequency bands

EU868 (863–870/873 MHz) in Europe;

AU915/AS923-1 (915–928 MHz) in South America;

US915 (902–928 MHz) in North America;

IN865 (865–867 MHz) in India; and AS923 (915–928 MHz) in Asia; LoRa enables long-range transmissions with low power consumption.

The technology covers the physical layer, while other technologies and protocols such as LoRaWAN (Long Range Wide Area Network) cover the upper layers. It can achieve data rates between 0.3 kbit/s and 27 kbit/s, depending upon the spreading factor.

LoRa devices have geolocation capabilities used for trilateration positions of devices via timestamps from gateways.

LoRa PHY

LoRa uses a proprietary spread spectrum modulation that is similar to and a derivative of chirp spread spectrum (CSS) modulation. Each symbol is represented by a cyclic shifted chirp over the frequency interval (f0-B/2, f0+B/2) where f0 is the center frequency and B the bandwidth of the signal (in Hertz).

LoRaWAN

Since LoRa defines the lower physical layer, the upper networking layers were lacking. LoRaWAN is one of several protocols that were developed to define the upper layers of the network. LoRaWAN is a cloud-based medium access control (MAC) layer protocol, but acts mainly as a network layer protocol for managing communication between LPWAN gateways and end-node devices as a routing protocol, maintained by the LoRa Alliance.

LoRaWAN defines the communication protocol and system architecture for the network, while the LoRa physical layer enables the long-range communication link. LoRaWAN is also responsible for managing the communication frequencies, data rate, and power for all devices. Devices in the network are asynchronous and transmit when they have data available to send. Data transmitted by an end-node device are received by multiple gateways, which forward the data packets to a centralized network server. Data are then forwarded to application servers. The technology shows high reliability for the moderate load. However, it has some performance issues related to sending acknowledgements.

LoRa Architecture

LoRaWAN defines the communication protocol and the system architecture, while LoRa defines the physical layer. Here is a typical system architecture of a LoRaWAN node.

LoRa Network Architecture

Most of the modern IoT LAN technologies use mesh network architecture. By using mesh network, the system can increases the communication range and cell size of the network. But, nodes in a mesh network has additional responsibility of forwarding messages to other nodes, typically irrelevant to them. This affect the device battery life significantly.

LoRaWAN uses star topology as it increases battery lifetime when long-range connectivity is used.

LoRa network consists of several elements.

LoRa Nodes / End Points: LoRa end points are the sensors or application where sensing and control takes place. These nodes are often placed remotely. Examples, sensors, tracking devices, etc.

LoRa Gateways: Unlike cellular communication where mobile devices are associated with the serving base stations, in LoRaWAN nodes are associated with a specific gateway. Instead, any data transmitted by the node is sent to all gateways and each gateway which receives a signal transmits it to a cloud based network server. Typically the gateways and network servers are connected via some backhaul (cellular, Wi-Fi, ethernet or satellite).

Network Servers: The networks server has all the intelligence. It filters the duplicate packets from different gateways, does security check, send ACKs to the gateways. In the end if a packet is intended for an application server, the network server sends the packet to the specific application server.

Using this type of network where all gateways can send the same packet to the network server, the need of hand-off or handover is removed. This is useful for asset-tracking application where assets move from one location to another.