 The control channels supported by MAC can be classified as follows (see Figure 7-19): Broadcast Control Channel (BCCH): a downlink channel for broadcasting system control information. 306 CHAPTER 7 The IEEE 802. 16m MAC CPS (Part II) Radio Bearers Security Security Segmentation Segmentation Logical Channels Scheduling / Priority Handling Multiplexing Transport Channels FIGURE 7-17 LTE Layer 2 structure in the uplink [9] Paging Control Channel (PCCH): a downlink channel that transfers paging information and system information change notifications. This channel is used for paging when the network does not know the location of the UE. Common Control Channel (CCCH): a channel for transmitting control information between UEs and eNBs. This channel is used for UEs having no RRC connection with the network. Multicast Control Channel (MCCH): a point-to-multipoint downlink channel used for transmitting MBMS control information from the network to the UE, for one or several MTCHs. This channel is only used by UEs that receive MBMS. Dedicated Control Channel (DCCH): a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. It is used by UEs that have RRC connection. The traffic channels are exclusively used for the transfer of user-plane information. The traffic channels supported by MAC can be classified as follows (as shown in Figure 7-20): Dedicated Traffic Channel (DTCH): a point-to-point bi-directional channel dedicated to a single UE for the transfer of user information. Multicast Traffic Channel (MTCH): a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. This channel is only used by UEs that receive MBMS. 7.4 3GPP LTE radio link control and medium access control sub-layers UPPER LAYERS MAC Control Logical Channel Prioritization (UL only) Control Multiplexing/Demultiplexing Functions Random Access Control DL-SCH UL-SCH LOWER LAYER FIGURE 7-18 3GPP LTE UE MAC structure [10] Logical Channels Control Channels Traffic Ch