n protocol with the BS based on the primary security association. The access RS uses a set of active keys shared with the BS to perform encryption/decryption and integrity protection on the relay link. The MAC PDUs are encapsulated within one relay MAC PDU and are encrypted or decrypted by primary security association, which is established between the RS and the BS. The security contexts used for the relay link (between a BS and an RS) and the access links (between an RS and an MS) are different and are maintained independently. The key management the same as that performed by a macro BS. Figure 3-16 shows the IEEE 802. 16m relay station protocol stack. An RS may consist of a subset of the protocol functions shown in Figure 3-16; however, the ingredients of each subset of functions depend on the type or category of the RS, as well as other deployment requirements. The functional "Time-division transmit and receive is a relay mechanism where transmission to subordinate station and reception from the super-ordinate station or transmission to the super-ordinate station and reception from the subordinate station is separated in time. CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure Relay Location Management Functions Multi-Carrier Mobility Management E-MBS Network-entry Self Organization Security Management Management Fragmentation/Packing Radio Resource Control and Management (RRCM) Medium Access Control (MAC) Multi Radio Sleep Mode Scheduling and Coexistence Management Resource Multiplexing PHY Control Control MAC PDU Formation Data Forwarding Interference Link Adaptation Management Ranging (CQI, HARQ, power Signaling control) Control-Plane Data-Plane PHY SAP PHY Protocol (FEC Coding, Signal Mapping, Modulation, MIMO processing, etc.) Physical Layer FIGURE 3-16 Protocol structure of the IEEE 802.16m relay stations [12] blocks and the definitions provided in this section do not imply their support in all IEEE 802.16m RS implementations. The IEEE 802.16m relay capabilities are partially (and conceptually