LoRa is an open radio standard of a Low Power Wide Area Network (LPWAN) for only small amounts of data. Therefore it’s suitable for a long-range.
As for LoRaWAN, it is the name for a radio network based on LoRa. LoRa and uses frequency bands from the license-free ISM bands. This means that a LoRaWAN can be an alternative or supplement to the traditional mobile network with a central network operator. What’s more, a LoRaWAN is also referred to as a 0G network to differentiate it from traditional mobile communications.
Since LoRa is an open radio standard, anyone can set up a LoRaWAN as an IoT or M2M network with bidirectional communication or use a community-based solution.
Note: American LoRaWAN is different from European LoRaWAN. This has an impact on the transmission rate and thus also on energy consumption.
Characteristics
• Connection: Uplink-oriented, bidirectional, acknowledgment mode possible
• Modulation: Chirp Spread Spectrum and FSK
• Network architecture: The end devices communicate with gateways, which transmit the data packets to a server. The server has interfaces for connecting to IoT platforms and applications.
• Frequency ranges: 868 MHz (863–870 MHz, divided into several subbands) in Europe and 915 MHz in the USA. The channel usage period is limited by regulations in many countries (duty cycle).
• Range: Depending on the topography, up to 2 km in urban areas and up to 15 km in rural areas. Good penetration of buildings is achieved.
• Energy consumption: Between 10 mA and 100 nA in sleep mode. Depending on the application, the battery life is 2 to 15 years.
• Radio channel bandwidth: 125 kHz
• Sensitivity: -137 dBm
• Transmission power: +20 dBm or a maximum of 25 mW
• Data packets: EU: max. 51 bytes / USA: max. 11 bytes of user data per packet
• Transfer rate: Between 250 bit / s and 50 kbit / s
Transmission Technology
To achieve high efficiency in data transfer and energy consumption, LoRaWAN uses a frequency spread. It allows interference to be largely avoided and narrowband interference to be avoided.
The transmission method is called “Chirp Spread Spectrum”. And the signal transmission takes place as a kind of chirping. Then, the chirped pulse is spread over a wide frequency range. The bandwidth can optionally be used for a high data rate or a robust transmission. The spread factor and the bandwidth determine how high the data rate can be and how high the probability of reception is.
Signals that are modulated with different spreading factors and transmitted over the same frequency channel do not interfere with each other. The orthogonality of the spreading factors enables the simultaneous transmission of several end devices on the same channel.
The LoRa signals are very robust against in-band and out-of-band interference. Their insensitivity to multipath reception or fading ensures a long-range in urban areas.
LoRaWAN Network Architecture
The LoRaWAN network architecture consists of many end devices in the form of sensors and actuators, several gateways and a central network server. The terminal device communicates with the gateway. The gateway connects to the network server. Then the network server communicates via various protocols (e.g. REST, MQTT, etc.) with an application that is operated, for example, as an application in the cloud.
In a LoRaWAN, gateways are the receivers for the radio signals at 868 MHz. Here the LoRa chips receive the chirp signals. As for gateways, on the other hand, connect to the Internet.
The gateways of a LoRaWAN ideally form a close-knit network and can be distributed all over the world.
A message can be received by one or more gateways. The gateways forward these to the network server without further intervention.
In a LoRaWAN, the network servers are responsible for identifying the sender and forwarding the package to an application server.
The network server ensures, among other things, that a message arrives only once at the application server, regardless of how many gateways have received it.
Private or Community Network
Basically everyone can operate their own LoRaWAN. Since LoRa works in the non-assigned frequency range, no license costs for frequencies are necessary.
If you only have to set up a LoRaWAN in a limited area, the operation of your own gateways and servers can make sense.
However, if you are dependent on a wide-area radio network, you can also contact MOKOSmart, we only operate our own gateway, which speaks to the servers over the Internet. With regard to security, you only have to trust the network server to deliver the received data packets and the application server, which can decrypt the content.
Range
LoRa has a high sensitivity of -137 dBm, which increases the availability of the network. The signals penetrate building walls without any problems and can also reach cellars or other so-called deep indoor locations.
The distance between the transmitter and the receiver is approximately 3 km (city), approx. 6 km (suburbs) and up to 13 km (rural areas) depending on the surroundings and built-up areas.
The distance between the LoRa transmitter and the receiver depends on the spreading factor, the bandwidth, the selected transmission power of the LoRa Chip and the antenna used.
Transfer Rate
To maximize battery life and control overall network capacity (limited by regulatory requirements), LoRa controls the data rate and RF output individually using adaptive data rate (ADR) for each end device.
Communication between the terminal and gateway takes place on different frequency channels with different data rates. The range of data is 0. 3 to 50 kbit/s. The physical package size is 64 bytes. 13 bytes are required for the header. This leaves 51 bytes for the user data.
Note: in the United States, channel time is capped at 400 milliseconds. This means that only a maximum of 11 bytes of user data can be transmitted per packet.
The SF12 (spreading factor) at 125 kHz (bandwidth) only achieves 250 bit / s (data rate). The receiver is very likely to perceive the chirp pulse because it is comparatively easy for it to distinguish the signals from the noise.
The fastest specified combination is SF7 at 250 kHz bandwidth. This leads to 11,000 bps.
Power Consumption
The LoRa modulation process enables optimal transmission power with the lowest possible power consumption by the transmitter. The low energy consumption enables battery life of up to 15 years.
This simplifies handling and is inexpensive because no separate power supply is required.
Classes of Devices
LoRa differentiates between different device classes, whereby only class A is interesting for applications in the Internet of Things. And the end device is in a battery-saving state and only transmits briefly when the state changes. Something can only be sent to the terminal during this time.
Together with the radio module, these end devices are very inexpensive because of their simplicity and are also suitable for covering a high demand.
If devices can also be addressed outside this period, device class B or C must actually be selected, which greatly increases power consumption and, depending on the network, is not supported at all.
Applications
LoRa is primarily made for static sensor applications. Typical applications include recording, querying and exchanging status information. With sensors located at any location, information can be determined or obtained, which can be easily integrated into an application.
1. Smart Home
2. Smart City
3. Smart Factory
4. Smart Farming
5. Smart Transport
