An Introduction to LoRa Technology
Monday, July 6, 2015
LoRaWAN is a Long Range, Low Power Wide Area Network (LPWAN) specification designed for the Internet of Things. It emphasizes secure bi-directional communication, mobility, and localization services to provide simple, seamless interoperability among smart Things.
Gateways connected to the network server via standard IP connections relay messages between end-devices using single-hop wireless communication and a central network server in the backend. The end-point communication supports bi-directional communication as well as multicast enabling software, upgrades over the air, and other mass distribution messages.
LoRa spreads communication between end-devices and gateways across multiple frequency channels and data rates. The spread spectrum technology uses data rates ranging from 0.3 kbps to 50 kbps to prevent communications from interfering with each other, and creates a set of "virtual" channels that increase the capacity of the gateway. To maximize both the battery life of the end-devices and the overall network capacity, the LoRa network server manages the data rate and RF output for each end-device individually through an adaptive data rate (ADR) scheme. LoRa also addresses the need for security by providing encryption at the network level, application level, and device level through the use of a unique network key (EUI64), a unique application key (EUI64), and a device-specific key (EUI128).
LoRa has several classes of end-point devices to address the different application needs:
- Bi-directional end-devices (Class A): Class A end-devices allow for bi-directional communications in which each end-device's uplink transmission is followed by two short downlink receive windows. Downlink communications from the server at any other time will have to wait until the next scheduled uplink.
- Bi-directional end-devices with scheduled receive slots (Class B): Class B devices open extra receive windows at scheduled times in addition to the random receive windows described in Class A.
- Bi-directional end-devices with maximal receive slots (Class C): Class C end-devices of have nearly continuously open receive windows, only closed when transmitting.
Key Features of LoRA:
- >160 dB link budget
- +20 dBm TX power
- Exceptional IIP3
- 10dB selectivity improvement over FSK
- Tolerant to in-channel burst interference
- Lowest RX current - 10mA
- Lowest sleep current
- Ultrafast wake-up (sleep to RX/TX)
- Longest Range
- Robust Links
- Extended Battery Life
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