acket delivery. The ARQ entity in the transmitter can then initiate re-transmission and re-segmentation of the ARQ blocks that correspond to the failed HARQ packet. 7.3 MAC PDU FORMATION Figure 7-12 illustrates the MAC PDU construction process, input and output of each functional block, and the order in which those functions are applied for various types of connections, i.e., ARQ, non- ARQ, and control connections. The payloads associated with multiple transport connections corre- sponding to the same security association can be multiplexed and encrypted together in a MAC PDU. If N transport connections are multiplexed, one MEH and one FEH, PEH, RFPEH, and MCEH per connection are present in a MAC PDU. The AGMH and the MEH headers carry the information about the Flow IDs and lengths of the payloads. The FEH, PEH, and RFPEH headers carry the information CHAPTER 7 The IEEE 802.16m MAC CPS (Part II) Convergence Sublayer Service Flow Classification MAC Control Functions Header Suppression Messages Messages MAC SDU MAC SDU MAC SDU MAC SDU Fragmentation SDU Fragmentation/Packing Function Signating MAC PDU MAC PDU MAC PDU MAC PDU Payload Payload Payload Payload MAC PDU MAC PDU Payload Payload MPDU Formation Multiplexing Security (Encryption/Authentication) MAC PDUs Concatenation Function Concatenated MAC PDUs Physical Layer MAC CPS Data Plane Functional Blocks Control Connection Transport Connections (ARQ) Transport Connections (non ARQ) FIGURE 7-12 The MAC PDU construction process on the data-plane [1] 7.3 MAC PDU formation Convergence Sublayer MAC SDUs MAC SDUs Flow ID = A Flow ID = B Unencrypted Payload A Unencrypted Payload B Integrity Check PN, EKS Encrypted Payload A Encrypted Payload B Value (ICV) Unencrypted Encrypted PDU Headers Other Extended Integrity Check Headers PN,EKS Encrypted Payload A Encrypted Payload B Value (ICV) Unencrypted Headers Encrypted PDU FIGURE 7-13 Multiplexing of connection payloads associated with the same security association [2] about the transport connection payload and MCEH carries in