nt slot within the current sidelink subframe PSSCH jmod10, where j is equal to the subscript of IPSSCH for sidelink transmission modes 1 and 2, respec- tively; and ie {0,1} is the number of the current slot within the current sidelink subframe PSSCH = kmod10 in which k is equal to the subscript of ISL for sidelink transmission modes 3 and 4. The last SC-FDMA symbol in a sidelink subframe is used as a guard period and is not used for sidelink transmission [3,5]. 7.4.2 Sidelink Physical Channels 7.4.2.1 Physical Sidelink Shared Channel In LTE-based sidelink communication, the processing of the sidelink shared channel (SL-SCH) follows the procedures for LTE downlink shared channel processing with some differences as follows: (1) data arrives at the channel coding unit in the form of a maximum of one TB in every transmission time interval; (2) in the step of code block concatenation, the sequence of coded bits corresponding to one TB after code block concatenation is referred to as one codeword; and (3) physical uplink shared channel (PUSCH) interleaving is applied without any control information in order to apply a time-first rather than frequency- first mapping, where For SL-SCH configured by higher layers for V2X sidelink, is used [3,5] (Fig. 7.24). 824 Chapter 7 Figure 7.24 Transport block processing for PSSCH [4]. The PSSCH processing begins with the scrambling of the block of bits b(0), b(Nbit where Nbit is the number of bits transmitted on the PSSCH in one subframe. The scrambling sequence generator is initialized with Cinit = n 2014 + nPSSCH29 nssf + 510 at the start of each PSSCH subframe. For sidelink transmission modes 1 and 2, = nSp is the destination identity obtained from the sidelink control channel, and for sidelink transmission modes 3 and 4 = L-1 with p and L equal to the decimal representation of CRC on the PSCCH transmitted in the same subframe as the PSSCH [3]. The output of the scrambling function is modulated using QPSK or 16QAM modulation and layer-mapped assuming a single antenna port [3]. Tr