Wirnet™ i-series

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====== LoRa Modem management ======

{{ :images:schem_ibts_topology.png??600 |}}

===== How is the data from an end-device transmitted to a LoRa Network Server (LNS) =====
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.\\

===== LoraWan protocol =====
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 {{https://www.lora-alliance.org/what-is-lora|website}}. If you are new to the LoRa technology, the "LoRaWAN™ 101 – A Technical Introduction" document is a good way to start.

===== LoRa specific hardware =====


{{:images:loraloc_hardware_architecture.png?800|}}

Wirnet™ iBTS gateways are composed of multiple boards. The LoRaLOC boards are responsible for the management of LoRa packets. Depending on the Wirnet™ iBTS hardware versions, up to 4 LoRaLOC board can be integrated into the gateway.

Each LoRaLOC board is composed of:
	- 1 frontend 
	- 1 AD9361
	- 2 SX1301
	- 1 FPGA
	- 1 SX1239

Each SX1301 is capable of demodulating 8x 125KHz LoRa bands, 1x 250KHz LoRa bands and 1x FSK band. Since there are 2x SX1301 in each LoRaLOC, a LoRaLOC can use up to 16x 125KHz LoRa bands.

Each frontend has 2x SMB antennas ports. To use both SX1301, only one antenna can be used. Actually, using 2 antennas is only useful to cover a wider area. For example, two directional antennas could be used from the same place or two omnidirectional antennas could be used from different places.

Each LoRaLoc is calibrated on a testbench. The result of the calibration process is copied at each startup in the ''/tmp/calib_loraloc.json'' file.

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

Kerlink provides a Hardware Abstraction Layer (HAL) to use the LoRa Specific hardware. The 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.

More details about the HAL and its debug tools [[wiki:hal|here]].

<note tip>A revoir </note>

===== Kerlink common packet forwarder (cpf) =====
The packet forwarder is the program used to send the packets it received from the end-devices to the LNS and vice-versa, hence its name.

More details about the cpf [[wiki:cpf|here]].		

<note tip>A revoir</note>
===== Regulation =====
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 gateway, make sure that your LNS configuration fits with your country regulation. 

The LNS doas not handle LBT feature (Listen Before Talk). A few countries (Japan and Korea) requires the use of the LBT feature, this feature is activated in the packet forwarder configuration.
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