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Introduction

The ChirpStack Gateway Mesh is a software component that can run on LoRa® gateways, turning these gateways either into Relay Gateways (gateways relaying data, most likely these gateways are solar powered) or Border Gateways (gateways terminating the mesh protocol and directly communicating with ChirpStack).

The aim of this component is to extend LoRaWAN® coverage, by adding LoRa gateways that are not connected to the internet which will repeat uplink and downlink LoRaWAN payloads. This can be useful in remote areas where internet coverage is sparse. This solution is different from the LoRa Alliance Relay Protocol, as no software implementation changes are required in the device stack.

It is possible that there are multiple Relay Gateways inbetween the End-Device and the Border Gateway. The technical limitation is 8 hops (the first Relay Gateway counts as the 1st), but this is also influenced by required airtime to receive and relay these payloads.

The ChirpStack Gateway Mesh component has been developed in collaboration with RAK.

ChirpStack Gateway Mesh architecture

GEnd DeviceEnd DeviceRelay Gateway 1Relay Gateway 1End Device->Relay Gateway 1LoRaWAN payloadRelay Gateway 2Relay Gateway 2Relay Gateway 1->Relay Gateway 2Mesh encapsulated LoRaWAN payloadBorder GatewayBorder GatewayRelay Gateway 2->Border GatewayMesh encapsulated LoRaWAN payloadChirpStackChirpStackBorder Gateway->ChirpStackLoRaWAN payload + Mesh context blob

End Device

LoRaWAN End Device, e.g. LoRaWAN 1.0.x or 1.1.x. Does not need modifications or implementation TS011 specification.

Relay Gateway

LoRa Gateway, e.g. SX1301/2/3 based (optionally + ISM2400 concentrator module). This gateway does not have an internet backhaul and could be solar powered. It runs the ChirpStack Gateway Mesh component which handles the relaying of uplink and downlink packages between the Relay Gateway and the Border Gateway. For the Relay Gateway <> Border Gateway, it might use the same radio band as the End Device, or it could use the ISM2400 band (based on hardware capabilities + use-case requirements).

In this setup, only the ChirpStack Concentratord and ChirpStack Gateway Mesh components must be installed on the gateway.

Gcluster_0LoRa® GatewayChirpStack Gateway MeshChirpStack Gateway MeshChirpStack ConcentratordChirpStack ConcentratordChirpStack Gateway Mesh->ChirpStack ConcentratordZeroMQ

Border Gateway

LoRa Gateway, which is internet connected. It handles the wrapping / unwrapping of the Mesh encapsulated LoRaWAN payloads. The Border Gateway <> ChirpStack communication is as if the Border Gateway is directly communicating with the End Device. The only exception is that on uplink it sets a context with Mesh specific data, which must be returned by ChirpStack on downlink.

In this setup, the ChirpStack Concentratord, ChirpStack Gateway Mesh and ChirpStack MQTT Forwarder must be installed on the gateway. ChirpStack MQTT Forwarder will in this case be configured to use the ChirpStack Gateway Mesh API interface instead of the ChirpStack Concentratord.

Gcluster_0LoRa® GatewayChirpStack Gateway MeshChirpStack Gateway MeshChirpStack ConcentratordChirpStack ConcentratordChirpStack Gateway Mesh->ChirpStack ConcentratordZeroMQChirpStack MQTT ForwarderChirpStack MQTT ForwarderChirpStack MQTT Forwarder->ChirpStack Gateway MeshZeroMQMQTT BrokerMQTT BrokerChirpStack MQTT Forwarder->MQTT BrokerMQTT

ChirpStack

ChirpStack will receive the uplink from the Border Gateway, with the RX parameters from the Relay Gateway. Thus it receives the original:

  • Data-rate
  • Frequency
  • RSSI
  • SNR

Returning the uplink context "blob" on downlink, it is able to transmit downlinks to the End Device.