Physical certification testing is required to assure interoperability. Likely, this will vary from vendor to vendor. WiMAX Forum members assert that their products hold the inside track to successful WiMAX CERTIFICATION™. Several vendors have asserted that their precursor gear will be forward compatible with future WiMAX CERTIFIED™ gear. This is a crucial step that began paving the way for commercial deployments this past year.  

It might be better to state that vendors have an overriding need for their precursor radios to work with Certified products even if a firmware upgrade is necessary. It is unlikely that hardware upgrades will be necessary for Fixed WiMAX upgrades, but some vendors eager to launch early precursor 802.16e units, planned for specific hardware upgrades in order to launch early.