Get link quality from a coap client

[kaushalyasat]

Hi,

I want to get a measure of link quality of a OpenThread network from the CoAP client side. I have used 'otThreadGetParentAverageRssi ()' from the client to get RSSI seen from the parent (?), which seems to decrease when distance between the server and client increases.  I would like to get a similar measure on link quality of the total link. I tried 'otThreadGetParentInfo'. It seems to give the Link Quality In but that value seems static!! Does not change when the distance between them is almost at max. So I would like to know

1. Why otThreadGetParentInfo () not reporting correct link quality with distance?

2. Is there a better way to retrieve link quality info?

Cheers,

Kaushalya 

P.S. I am at the end of my development cycle, so if you can give me a quick reply, it is much appreciated.

[kaushalyasat]

Hi, Strange, the link quality seems to be working today. I will keep an eye on this. Are there any conditions this 'otThreadGetParentInfo()' could fail? I must confess I have not tested the return value to be 'OT_ERROR_NONE'.

Cheers,

Kaushalya

[haakonsh]

Hmm the API docs for otThreadGetParentInfo does not define a list of valid return values, and that is a bit strange given that the function header clearly expects a return value. I suggest you monitor this return value. 

Also, RSSI is not a direct representation of Link Quality so their values will not match. I don't know the LQI algorithm that is used for 802.15.4/OpenThread, but I suspect that that it aggregates more datapoints than RSSI, then filter and fuse the data into a single variable called Link Quality. The response-time of the LQI algo is likely way slower than the RSSI sample rate, who is probably updated for every packet received.