an overall quality parameter for a cpe

Hi all.
I would test periodically all my users.
My idea is to connect each cpe ad do some tests to evaluate the overall quality of connection.

in addition to usual singnal strength (but it only shown signal from cpe to ap), do you think ping speed (speed test is all invasive) could be an overall paameter of link quality from cpe to gateway ?
or exists something better ?

Thanks.

I guess you could log the time taken to transfer a test file size from AP to CPE?

yes, but the transfert time doesnt give info about (i.e.) packet loss.