A method and apparatus of providing a piggybacked positive acknowledgement/negative acknowledgement (ACK/NACK) (PAN) field indicator (PANI) and a polling indicator are disclosed. A combined field of a PANI bit, a relative reserved block period (RRBP) bit and an EGPRS supplementary polling (ES/P) field may indicate a polling scheme and a presence of a PAN field. Alternatively, the presence of the PAN field in the data block may be indicated by using a specific training sequence. Alternatively, a forward error correction (FEC) coding may be performed on the data block including the header, and the presence of the PAN field may be indicated by scrambling the encoded bits corresponding the header with a specific scrambling sequence. Alternatively, a header check sequence (HCS) may be generated and the presence of the PAN field is indicated by mixing a predetermined sequence with the HCS.