LoRaWAN Tutorial 101 - Basics
LPWAN, LoRa and LoRaWAN
A low-power wide-area network (LPWAN) is a type of wireless wide area network designed to allow long-range communications at a low bit rate among things, such as sensors operated on a battery. LPWAN offers battery life of several years and is designed for sensors and applications that need to send small amounts of data over long distances usually at a duty cycle of one message per hour or lower.
LoRaWAN is a non-cellular LPWAN in which LoRa modulation scheme forms the physical layer (PHY - Layer 1 of OSI Model ) while LoRa MAC from LoRa Alliance forms the data link and network layer (Layer 2 and 3 of OSI Model). The LoRa Physical Layer (PHY) together with LoRa MAC forms the LoRaWAN Protocol. The layers are illustrated below :
LoRa in India
LoRa physical layer contains the LoRa Radio Layer as well. The radio layer should be configured to work in the regional ISM band. In India context, the only ISM band that meets the 125 KHz Bandwidth requirement and that coincides with global LoRa frequency bands is the 865-867 MHz Band. To know more about the 865-867 MHz channel regulations, please see the Gazette notification from Wireless Planning and Coordination Wing here.
It is illegal to use LoRa in 433 MHz band as it only supports a maximum bandwidth of 10KHz. It also has severe Tx Power limitations. To know more about the 433 MHz channel regulations, please see the Gazette notification from Wireless Planning and Coordination Wing here.
LoRa Alliance and LoRaWAN Protocol
The LoRa Alliance is an open non-profit organization that promotes its Long-Range WAN (LoRaWAN) protocol as an open global standard. LoRa Radio (without MAC) can be used in standalone mode for P2P communications between nodes but LoRa Alliance defines a star network under the LoRa MAC Layer, where nodes talk to gateways over an end-end encrypted connection . We won't be talking about LoRa P2P from now on but if you are curious to use LoRa without a gateway, an implementation can be found here.
Based on LoRa MAC layer operation there are three classes of end devices in a LoRaWAN. Classes help to categorise devices based on the type of connection which essentially defines its power consumption and availability of Uplink(s) and Downlink(s). The classes are defined as Class A, Class B and Class C. These three different classes devices are designed to address different needs for a wide range of applications. All of the three classes support bidirectional communication.
LoRa Alliance Specifications for India
LoRa Alliance has released specifications for Indian Channel under the title IN_865_867. Page 58 of LoRa Regional Parameters v1.0.3 has details of IN_865_867 Channel Plan. The document can be found here. Channel Plan, in summary, is shown below:
Image Credit: TheThingsNetwork
Indian Channel Plan allows for upto 16 Channels. The three channels for Uplink/Downlink and one dedicated channel for Downlink ( RX2) needs to be supported by all the devices while rest of the channels may be configured as per network requirements.
Next Chapter: LoRaWAN Tutorial 102 - Architecture [Available on 16/11/2018]