1. A method implemented in an apparatus for wireless communication, comprising: dynamically scheduling a user equipment (UE) with a resource allocation of at least one downlink (DL) virtual resource block (VRB); and determining an uplink (UL) acknowledgement (ACK) Identifier (ID) for the UE based on the at least one DL VRB, the UL ACK ID being associated with a time-varying cyclic shift of a base sequence.