ntrol information between a UE and the network Common Control Channel (CCCH) Bi-directional channel for transmitting control information be- tween network and UEs Shared Channel Control Channel (SHCCH) Bi-directional channel that transmits control information for uplink and downlink shared channels between network and UEs Traffic Channel (TCH) Dedicated Traffic Channel (DTCH) A DTCH is a point-to-point channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both up- link and downlink. Common Traffic Channel (CTCH) A point-to-multipoint unidirectional channel for transfer of dedi- cated user information for all or a group of specified UEs. 3.8.3.1.3 Mapping between logical channels and transport channels Table 3.5 illustrates connections between logical and transport channels: Table 3.5 Connections Between Logical and Transport Channels Channel Connected to BCH, may also FACH RACH and FACH SHCCH RACH, USCH/FACH and DSCH Either RACH and FACH; RACH and DSCH to DCH and DCSCH, DCH AND DSCH, DCH, CPCH (FDD only) or USCH (TDD only9 Either RACH and FACH, RACH and DSCH, DCH and DSCH, DCH, CPCH (FDD only), FAUSCH, USCH (TDD only) Figures 3.14 and 3.15 illustrate the mappings as seen from the UE and UTRAN sides including both the FDD and TDD modes. The UMTS Development Platform BCCH- PCCH- DCCH- CCCH- SHCCH- CTCH- DTCH- MAC SAPs (TDD only) Transport BCH PCH CPCH FAUSCH RACH FACH USCH Channels (FDD only) (TDD only) Figure 3.14 Logical channels mapped onto transport channels, seen from the UE side [9]. BCCH- PCCH- DCCH- CCCH- SHCCH- CTCH- DTCH- (TDD only) MAC SAPs Transport BCH PCH CPCH FAUSCH RACH FACH USCH DSCH DCH Channels (FDD only) (TDD only) Figure 3.15 Logical channels mapped onto transport channels, seen from the UTRAN side [9]. 3.8.3.2 MAC Functions The functions of MAC include: Mapping between logical channels and transport channels. Selection of appropriate transport format for each transport channel depending on instantaneous source rate. Priority handling between data flows of one 