ubframe. The overall LTE-based V2X sidelink physical layer processing is shown in Fig. 7.16. 814 Chapter 7 Sidelink baseband processing MIB-SL Transport channel Physical signals discovery TB Physical channel and layer-1 signal generation and SCI format 0/1 RF processing processing processing OFDM modulation V2X traffic SL-BCH, SL-DCH, SL-SCH PSBCH, PSDCH, PSCCH, SL-DMRS, PSSS, SSSS PSSCH Code block Demodulation Synchronization segmentation and Scrambling reference signals CRC attachment signals TB CRC attachment Modulation Mapping of symbols to physical resources Transform SC-FDMA Signal Channel coding precoding generation Mapping to Rate matching physical resources Interleaving Figure 7.16 LTE V2X sidelink physical layer processing [17,22]. The C-V2X specifies two subchannelization schemes, as shown in Fig. 7.17: (1) adjacent PSCCH + PSSCH, where the SCI and TB are transmitted in adjacent RBs. For each SCI + TB transmission, the SCI occupies the first two RBs of the first subchannel utilized for the transmission. The TB is transmitted in the RBs following the SCI, and can occupy several subchannels depending on its size. It will also occupy the first two RBs of the fol- lowing subchannels; and (2) non-adjacent PSCCH + PSSCH, where the RBs are divided into pools. One pool is dedicated to transmit only SCIs, and the SCIs occupy two RBs. The second pool is reserved to transmit only TBs and is divided into subchannels. The TBs can be transmitted using QPSK or 16QAM modulation, whereas the SCIs are always transmitted using QPSK. The C-V2X uses turbo coding with normal cyclic prefix. There are 14 OFDM symbols per subframe, and four of these symbols are dedicated to the transmission of demodulation reference signals (DM-RS) in order to improve robustness against the Doppler effect at high speeds. The reference signals are transmitted in the third, sixth, ninth, and twelfth symbol of the subframe. The maximum transmit power is 23 dBm, and the stan- dard specifies a sensitivity-power-level requirement at the receiver of 