WP7502 AGPS do not work

Our project is using WP7502.
We test it in China, so that China UnionCom SIM is used.
The module can stream video now, that mean the data modem can work.

As the GPS fix time is long, we try to use AGPS.
My understanding of AGPS is that device need to access SUPL server to get data,
so that it can help GPS device fix location quickly.

We use below AT command to set the SUPL server:-

I have ping above server, make sure it can be accessed in China.

But seems that it does not work, because the fix time is still long.

Do I have any misunderstand about the AGPS?