rol, multiplexing, message acknowledgement, piggyback bandwidth request, MAC PDU length extension, ARQ feedback, and ARQ feedback polling extended headers. Type-specific header contents (variable): a type-specific and variable-sized field that will be elaborated on in the remaining parts of this section. An example is provided in Figure 6-7. Table 6-1 provides a complete list of extended header types, their descriptions, use cases, and important parameters. Note that the extended header group is never encrypted. Extended FEH/PEH/ Connection Header(s) RFPEH/MCEH Payload MAC PDU with Single Connection Payload FlowID(4) = X Length (3) Length(8) FEH/PEH/ FEH/PEH/ Connection Connection Extended RFPEH and RFPEH and Header(s) Payload Payload MCEH (flow x) MCEH (flow y) Flow ID=x Flow ID=y NI FI Type (4 bits) (4 bits) FID (4 bits), LI (1 bit), Length (11 or 14 bits), Reserved (1 bit) FID (4 bits), LI (1 bit), Length (11 or 14 bits), Reserved (1 bit) EH Indicator Bitmap (Variable) MAC PDU with Multiple Connections Payload FIGURE 6-7 Example usage of FEH/PEH/RFPEH/MCEH and MEH in MAC PDU [2] Table 6-1 Extended Header Types and Associated Parameters in IEEE 802.16m [2] Extended Header Description Usage Parameters MAC SDU The FEH is included in the MAC Fragmentation of Fragmentation Control (FC) is a 2-bit field that Fragmentation PDU with SPMH/AGMH headers, if large MAC SDUs describes the relationship of the MAC PDU and the Extended Header the payload in the MAC PDU MAC SDU in terms of fragmentation (see Table 6-2) (FEH) contains only a fragment of the MAC Sequence Number (SN) is maintained per SDU. The FEH is also included in the connection. For non ARQ connection, SN MAC PDUs with AGMH header, if represents the MAC PDU Payload Sequence the payload in the MAC PDU Number and the SN value increments by one contains a non-fragmented MAC (modulo 1024) for each MAC PDU. For ARQ SDU which requires a sequence connection, SN represents the ARQ block number. sequence number. MAC SDU Packing The PEH is included in the MAC Packing of