Systems and methods are disclosed for performing combined grant-free and grant-based UL resource allocation. In a particular embodiment, a network entity sends a first type of UL transmission resource assignment selected from two types of UL transmission resource assignment mechanisms to a UE for grant-free transmission and a second type of UL transmission resource assignment from two types of UL transmission resource assignment mechanism to a UE for grant based transmission. The network entity then receives a first data transmission from the UE for grant free transmission using an assigned transmission resource and a second data transmission from the UE for grant based transmission using an assigned transmission resources. Other embodiments pertain to changing the resource allocation scheme from grant free to grant based for a UE, or vice versa. Examples reasons for doing so may include HARQ re-transmissions.