ADR chMask all false

ChirpStack Network Server
1

I have an RN2903 near the edge of range of a Laird RG191 gateway. I have seen the following packet several times, where LoRaServer sends an ADR packet with the chMash false for all the channels. Is this by design?

{
        "downlinkMetaData": {
            "txInfo": {
                "gatewayId": "c0ee40ffff29679a",
                "frequency": 926900000,
                "power": 20,
                "modulation": "LORA",
                "loraModulationInfo": {
                    "bandwidth": 500,
                    "spreadingFactor": 10,
                    "codeRate": "4/5",
                    "polarizationInversion": true
                },
                "board": 0,
                "antenna": 0,
                "timing": "DELAY",
                "delayTimingInfo": {
                    "delay": "1s"
                },
                "context": "tTvbxA=="
            }
        },
        "phyPayload": {
            "mhdr": {
                "mType": "UnconfirmedDataDown",
                "major": "LoRaWANR1"
            },
            "macPayload": {
                "fhdr": {
                    "devAddr": "00207d6f",
                    "fCtrl": {
                        "adr": true,
                        "adrAckReq": false,
                        "ack": false,
                        "fPending": false,
                        "classB": false
                    },
                    "fCnt": 181,
                    "fOpts": null
                },
                "fPort": 0,
                "frmPayload": [
                    {
                        "cid": "LinkADRReq",
                        "payload": {
                            "dataRate": 0,
                            "txPower": 0,
                            "chMask": [
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false
                            ],
                            "redundancy": {
                                "chMaskCntl": 7,
                                "nbRep": 0
                            }
                        }
                    },
                    {
                        "cid": "LinkADRReq",
                        "payload": {
                            "dataRate": 2,
                            "txPower": 0,
                            "chMask": [
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                false,
                                true,
                                true,
                                true,
                                true,
                                true,
                                true,
                                true,
                                true
                            ],
                            "redundancy": {
                                "chMaskCntl": 0,
                                "nbRep": 1
                            }
                        }
                    },
                    {
                        "cid": "RXParamSetupReq",
                        "payload": {
                            "frequency": 923300000,
                            "dlSettings": "08"
                        }
                    },
                    {
                        "cid": "RXTimingSetupReq",
                        "payload": {
                            "delay": 1
                        }
                    }
                ]
            },
            "mic": "183b0ee9"
        }
    },
    {
        "uplinkMetaData": {
            "rxInfo": [
                {
                    "gatewayId": "c0ee40ffff29679a",
                    "time": null,
                    "timeSinceGpsEpoch": null,
                    "rssi": -115,
                    "loraSnr": -0.2,
                    "channel": 6,
                    "rfChain": 1,
                    "board": 0,
                    "antenna": 0,
                    "location": {
                        "latitude": 0,
                        "longitude": 0,
                        "altitude": 0,
                        "source": "UNKNOWN",
                        "accuracy": 0
                    },
                    "fineTimestampType": "NONE",
                    "context": "tTvbxA=="
                }
            ],
            "txInfo": {
                "frequency": 905100000,
                "modulation": "LORA",
                "loRaModulationInfo": {
                    "bandwidth": 125,
                    "spreadingFactor": 8,
                    "codeRate": "4/5",
                    "polarizationInversion": false
                }
            }
        },
        "phyPayload": {
            "mhdr": {
                "mType": "UnconfirmedDataUp",
                "major": "LoRaWANR1"
            },
            "macPayload": {
                "fhdr": {
                    "devAddr": "00207d6f",
                    "fCtrl": {
                        "adr": true,
                        "adrAckReq": true,
                        "ack": false,
                        "fPending": false,
                        "classB": false
                    },
                    "fCnt": 192,
                    "fOpts": null
                },
                "fPort": 3,
                "frmPayload": [
                    {
                        "bytes": "AfWqPQy52nq1Wqw="
                    }
                ]
            },
            "mic": "8afe14f9"
        }
    },
2

They are not, see the second LinkADRReq mac-command (quick guess, you have configured uplink channels 8 - 15):

“chMask”: [
false,
false,
false,
false,
false,
false,
false,
false,
true,
true,
true,
true,
true,
true,
true,
true
],
3

Yes, I am running channels 8-15, but have had LoRaServer cause the RN2903 to shut down all the channels, I assume because of the first header payload above.

To be clear, should LoRaServer be sending that header entry, setting all the channels to false, only to include a second entry turning on the right channels?

4

Yes, how it works is that the first LinkADRReq mac-command turns off all channels, then the second mac-command will enable only channels 8 - 15. The device must handle this as an atomic block. See this note from the LoRaWAN Regional Parameters Specification:

image