Join Response Channel Issue

[Kenneth Martin]

I have the Conduit mLinux setup as a private network. According to: Introduction to LoRa, Network Architecture:
Rx Frequencies

Private:
Rx1 and Rx2:
Uplink Channel / 8

Public:
Rx1:
Uplink Channel % 8
Rx2: 923.3

I’m not sure why Private Rx2 freq. is Uplink/8 (this doesn’t seem to agree with specification), but my current question has to do with the Rx1 Join response frequency. It appears to always be 923.9 MHz irrespective of the Channel the Join request is sent on.

lora/00-80-00-00-04-00-03-d6/packet_recv {“chan”:5,”codr”:”4/5″,”data”:”AG5Kh/bfpPbe1gMABAAAgAAlyiQuRxE=”,”datr”:”SF10BW125″,”freq”:904.89999999999998,”lsnr”:8.8000000000000007,”modu”:”LORA”,”rfch”:1,”rssi”:-101,”size”:23,”stat”:1,”time”:”2017-01-23T20:54:25.795290Z”,”tmst”:1970970356}
lora/00-80-00-00-04-00-03-d6/joined
lora/00-80-00-00-04-00-03-d6/packet_sent {“codr”:”4/5″,”data”:”IGL+45ckF+ZGub5nEVsw9LM”,”datr”:”SF10BW500″,”freq”:923.89999999999998,”ipol”:true,”modu”:”LORA”,”ncrc”:false,”powe”:14,”rfch”:0,”size”:17,”tmst”:1971970356}
^K^Croot@mtcdt:~# nc –udp –listen –local-port 1784
lora/00-80-00-00-04-00-03-d6/packet_recv {“chan”:1,”codr”:”4/5″,”data”:”AG5Kh/bfpPbe1gMABAAAgABNson5ou0=”,”datr”:”SF10BW125″,”freq”:904.10000000000002,”lsnr”:9,”modu”:”LORA”,”rfch”:0,”rssi”:-102,”size”:23,”stat”:1,”time”:”2017-01-23T21:13:22.039315Z”,”tmst”:186874180}lora/00-80-00-00-04-00-03-d6/joined
lora/00-80-00-00-04-00-03-d6/packet_sent {“codr”:”4/5″,”data”:”IGC/rr05kbUJ94EMQ55Ajkg”,”datr”:”SF10BW500″,”freq”:923.89999999999998,”ipol”:true,”modu”:”LORA”,”ncrc”:false,”powe”:14,”rfch”:0,”size”:17,”tmst”:187874180}

The LoRaWAN Regional Parameters specification also states the Join1 response should be the same as the RX1 Channel Number:
“RX1 Channel Number = Transmit Channel Number modulo 8”

Does anyone have an explanation for this seeming inconsistency?

Note: When I change the End Point code to force it to receive the Join1 response at 923.9MHz, then the Join1 response is correctly received, otherwise, it is not.

From the log file (just verifies 923.9MHz, no need to read):

21:24:53:500|DEBUG| Mosquitto command received ‘joined’
21:24:54:129|DEBUG| is frame ready?
21:24:54:130|DEBUG| App Queue Length: 1
21:24:54:130|DEBUG| BestGateway: 800000a00004e9
21:24:54:130|DEBUG| Start
21:24:54:131|INFO| Frame transmitted to 06:00:00:01 via GW (00:80:00:00:a0:00:04:e9 Chan LC2 127.0.0.1:38343) Seq# 0
21:24:54:134|DEBUG| App Data Queue: 1 front size: 17 available: 242
21:24:54:134|DEBUG| check if front is join request 17 bytes
21:24:54:135|DEBUG| Start
21:24:54:135|DEBUG| Transmitted Frame data
================================
000 20 25 af c2 19 52 8e 24
008 71 57 ca 35 7e 58 6a 3d
010 d9

21:24:54:136|DEBUG| rx1Offset: 0 rx1Datarate: 10
21:24:54:136|DEBUG| Use JoinResponse Window Time
21:24:54:138|DEBUG| JSON tx: {
“txpk” : {
“codr” : “4/5”,
“data” : “ICWvwhlSjiRxV8o1flhqPdk”,
“datr” : “SF10BW500”,
“freq” : 923.89999999999998,
“ipol” : true,
“modu” : “LORA”,
“ncrc” : false,
“powe” : 14,
“rfch” : 0,
“size” : 17,
“tmst” : 18415356
}
}

21:24:54:141|INFO| Transmit UDP message to Gateway 186 bytes
21:24:54:143|DEBUG| Send on socket 190 bytes, payload len: 186
21:24:54:160|DEBUG| Set node active: 0
21:24:54:163|DEBUG| Send MQTT message
21:24:54:164|DEBUG| UDP message: lora/00-80-00-00-04-00-03-d6/packet_sent {“codr”:”4/5″,”data”:”ICWvwhlSjiRxV8o1flhqPdk”,”datr”:”SF10BW500″,”freq”:923.89999999999998,”ipol”:true,”modu”:”LORA”,”ncrc”:false,”powe”:14,”rfch”:0,”size”:17,”tmst”:18415356}
21:24:54:164|DEBUG| UDP port: 1784
21:24:54:200|DEBUG| Mosquitto command received ‘packet_sent’

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