h connection. EH_indicator bitmap (variable size) A bit in the EH_indicator bitmap indicates the presence or absence of FEH/PEH/RFPEH/MCEH in the EH group corresponding to a connection payload. For a connection payload only one extended header from FEH, PEH, RFPEH, and MCEH are present. The FEH/PEH/RFPEH/MCEH for the connection payloads (if present) appear after the MEH in the same order as that of connection payloads. MAC Control ACK This header may be used by BS and Acknowledgement MAEH sub-type (1 bit) indicates reception of Extended Header MS to indicate the reception of of MAC control a control message (MAEH) a specific MAC control message or message ACK_SN (6 bits) indicates that SN is retrieved from BR without STID header. When the MCEH of the MAC PDU with the Polling bit set a BS or an MS receives a MAC to 1. control message or MAC control Control Connection Channel ID (CCC ID) of the message fragment with the Polling MAC control message that is received. bit set to 1 in the MCEH, the BS or MS sends an MAEH or AAI_MSG- ACK message as an acknow- ledgement after receiving the complete message with the SN of the MAC control message PDU or the SN of the last received fragment, if fragmented. Piggyback PBREH is used when an MS uses Piggyback Num_of_PBR (4 bits) is the number of piggyback Bandwidth Request a piggyback bandwidth request for bandwidth request bandwidth requests. Extended Header one or more service flows. FID (4 bits) is the flow identifier. (PBREH) Request type (1 bit) indicates aggregate or incremental nature of the request. BR size (19 bits) indicates the amount of requested bandwidth. (Continued) Table 6-1 Extended Header Types and Associated Parameters in IEEE 802. 16m [2] Continued Extended Header Description Usage Parameters MAC PDU length The MAC PDU length extended Extension of the size The length field in MLEH provides the three most extended header header is added to the MAC PDU of MAC PDUs for significant bits of the extended length of the MAC (MLEH) when the MAC PDU length is larger l