Apurba
Depends on why you need to do that !
Database "dump" taken on lower ASE can be loaded into higher ASE.
After the database load when you issue "online database" command in higher version the database is stamped and upgraded to the new version. This change can not be understood by lower version if you try to load the dump from higher into a lower version ASE.
If you need to take just the data from higher ASE to lower ASE you can use import / export with BCP.
If you have expertise available you could also replicate the data from ASE 16 into ASE 15
HTH
Avinash