When doing IOT test, I encounter an issue. One sony mobile phone initiate detach request just 2 seconds after it attach to EPC successfully.
The attach request is a combined EPS/IMSI attach and the attach accept result is EPS only with EMM cause 'CS domain not available'.
Some one suggest it maybe due to the mismatch of the parameter PTI (procedure translation identifier) in the attach request and attach accept. I checked it and find PTI are the same in the two message.
I also tried another old type sony mobile phone, this old phone does not have such strange behavior.
After compare the attach request and attach accept messages of these two mobile phone, I did not find anything wired.
So does any one knows what is the reason behind?
