The classical communication case is:

• A LoRa end-device emits a packet and opens a short reception window after the emission.
  
• The gateway uses its LoRa specific hardware to receive the RF packet.
  
• A program installed on the gateway named “packet forwarder” retrieves the packet and forwards it to the LNS.
  
• The LNS analyses the packet.
  
• If the LNS decides to reply to this packet, it sends the answer back to the packet forwarder.
  
• The packet forwarder uses the hardware of the gateway to send the frame (during the reception window).
  
• The end-device receives the packet.
  

The protocol used by the end-device, the gateway and the LNS is the LoRaWAN protocol. You will find a presentation, a technical introduction, and the detailed specification on the official website.

The LoRa specific hardware differs from one type of gateway to another. It defines the capabilities of the gateways such as the number of channels, the diversity, the sensibility, …

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The LoRa specific hardware of the gateways is driven by an FPGA. This FPGA is regularly updated by Semtech to improve its performances, to add new features and to correct bugs.

Kerlink provides a Hardware Abstraction Layer (HAL) to use the LoRa Specific hardware. This HAL is a static library written in C. Each version of the HAL relies on a version of the FPGA, therefore to use programs that use the HAL, the first thing to do is to update the FPGA.

For almost all users, the use of the FPGA and of the HAL is transparent. Kerlinks provides a CPF (see next paragraph) that takes care of the FPGA update and integrates the HAL.

The packet forwarder is a set of two daemons (working together) used to send the packets received from the end-devices to the LNS and vice-versa, hence its name.

The packet forwarder is the main program of a LoRa gateway. It has to be installed to implement a LoRaWAN network.

More details about how to install/configure the CPF here.

Each country has different regulation about RF transmission. Since this is the LNS that schedules the LoRa packets and chooses the RF power used by the gateways, make sure that your LNS configuration fits with your country regulation.

LNS do not handle the LBT feature (Listen Before Talk). A few countries (Japan and Korea) requires it. This feature is directly activated in the packet forwarder configuration.