Gps test of sim7100e

Hi I’m using sim7100E 4g module , i test sms,call, other application they are worked correctly.
Now i wanna test gps with at command , according to sim7100_at_command that recommended by simcom , when i execute “at+cgpsinfo=100”
each 100 second they should return my fixed position, but in really they respond “+cgps:,”
please help me (my english is not good sorry about that )