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Lora-net / LoRaMac-node

Reference implementation and documentation of a LoRa network node.
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Class C on develop reports "No free channel found" #774

Closed ChrisEAlfred closed 4 years ago

ChrisEAlfred commented 5 years ago

We are on the develop branch at 180c8deff3697bb944e8d2aad188aac5899db2f8

I have tested on the NucleoL073 with the SX1276 and SX1262 in Class C, APB and keep getting:

###### ===== MCPS-Request ==== ######
STATUS      : No free channel found

The commit at 0bd3b6a498b362be95b6c0d7b925e92776df790e adds the following code to DEVICE_STATE_SEND to set the class after joining as class A:

                    mibReq.Type = MIB_DEVICE_CLASS;
                    LoRaMacMibGetRequestConfirm( &mibReq );

                    if( mibReq.Param.Class!= CLASS_C )
                    {
                        mibReq.Param.Class = CLASS_C;
                        LoRaMacMibSetRequestConfirm( &mibReq );
                    }

Changing the class to Class C ultimately calls SX126xSetOperatingMode( MODE_RX ) via OpenContinuousRxCWindow( ). So the mode is now MODE_RX.

BUT ...

When we return to execute:

NextTx = SendFrame( );

This tries to call Radio.IsChannelFree() which fails due to the mode not being idle.

djaeckle commented 5 years ago

Hi ChrisEAlfred,

thanks for the report. I will double check it.

djaeckle commented 5 years ago

Hi @ChrisEAlfred ,

i can confirm the issue for regions using LBT, namely AS923 and KR920 .

djaeckle commented 5 years ago

Hi,

it will take some time to apply a suitable fix. The problem is, that the LBT function changes the radio state and thus, its configuration. Here, we need to make sure, changing the configuration has no effect on other operations of the MAC, especially, if no free channel is available.

KwonTae-young commented 5 years ago

I am using v4.4.2 I tried to use the KR920 band

I am not able to use the KR920 due to the following message.

###### ===== MCPS-Request ==== ######
STATUS      : No free channel found

###### ===== MCPS-Request ==== ######
STATUS      : No free channel found

###### ===== MCPS-Indication ==== ######
STATUS      : Address fail

###### ===== MCPS-Request ==== ######
STATUS      : No free channel found

###### ===== MCPS-Indication ==== ######
STATUS      : Address fail

EDIT1. ClassA is fine.

ChrisEAlfred commented 4 years ago

Is there any way to turn off listen before speak for now? It is not required in Australia AS923.

Having listen-before-speak also reduces to reliability on class A. As we do not need it on AS923, might as well send the packet it might get through - it did before adding listen-before-speak.

This is seriously holding up a product.

mluis1 commented 4 years ago

The provided fix should solve the initial issue.

Currently, you may disable the functionality by changing the threshold value. You may change it to 0. Like this the device will think that the channel is always free.

Concerning the the LBT activation for AS923 is due to the fact that Japan is part of the AS923 region. Japan regulatory office mandates the usage of LBT. Thus, if one wants to sell devices using the same firmware on different countries including Japan, then the LBT must be activated.

In the future we will add an MCPS-Request which will allow disabling/enabling the LBT checks. By default we will set it disabled. Then it is up to the application layer to enable/disable the LBT when required.