SAP BW 7.3 (not HANA) connecting with S4/HANA

Hi Experts,

Our client is having SAP BW 7.3 which connecting with ECC6 currently but they are considering S4/HANA to replace their ERP ECC6 system.

As part of the assessment, we would like to find out what are the technical integration option to perform data extraction between SAP BW 7.3 and S4/HANA.

Please advise.

Thanks.