e., radio bearers) on the same transport channel is performed by the MAC sublayer. In sidelink communications, only one TB is generated per TTI. The sidelink specific services and functions of the MAC sublayer include radio resource selection and packet filtering for sidelink communication and V2X sidelink communication [6]. MAC sublayer provides different types of services that are represented by logical channels, where each logical channel is defined by the type of information it conveys. The logical channels are generally classified into two groups: (1) control channels (for the transfer of control-plane information) and (2) traffic channels (for the transfer of user-plane informa- tion), as shown in Fig. 7.29. The SBCCH is a sidelink logical channel for broadcasting side- link system information from one UE to another UE(s). STCH is a point-to-multipoint channel, for transfer of user information from one UE to another UE(s). This channel is used only by sidelink communication-capable UEs and V2X sidelink communication- capable UEs. Point-to-point communication between two sidelink communication-capable UEs is also realized with an STCH. As shown in Fig. 7.29, STCH logical channel can be mapped to SL-SCH transport channel and SBCCH logical channel can be mapped to SL-BCH transport channel. Sidelink Vehicle-to-Everything (V2X) Communications 833 STCH SBCCH Sidelink logical channels SL-DCH SL-SCH SL-BCH Sidelink transport channels Sidelink physical PSDCH PSSCH PSBCH PSCCH channels Figure 7.29 Mapping between sidelink logical, transport, and sidelink physical channels [6]. transport channels include SL-BCH, which is characterized by a predefined transport for- mat; SL-DCH that is characterized by a fixed size, predefined format, and periodic broad- cast transmission, as well as support for both UE autonomous resource selection and scheduled resource allocation by the eNB. It is subject to collision risk due to support of UE autonomous resource selection; however, no collision is expected when UE is allocated dedi